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%\comment{HST SL9 summary paper}
\def\refhstslscisum{
{Hammel, H.\ B., R.\ F.\ Beebe, A.\ P.\ Ingersoll, G.\ S.\ Orton, J.\
R.\ Mills, A.\ A.\ Simon, P.\ Chodas, J.\ T.\ Clarke, E.\ De Jong, T.\
E.\ Dowling, J.\ Harrington, L.\ F.\ Huber, E.\ Karkoschka, C.\ M.\
Santori, A.\ Toigo, D.\ Yeomans, R.\ A.\ West}
{1995}
{HST Imaging of Atmospheric Phenomena Created by the Impact of Comet
Shoemaker-Levy 9}
{Science}
{{267}{1288}{1296}}
{Hammel \etal}
{}
{}
{H.\ B.\ Hammel \etal}}
%\comment{Comet Shoemaker-Levy 9 impact prediction paper}
\def\refjhcslprednat{
{Harrington, J., R.\ P.\ LeBeau, K.\ A.\ Backes, and T.\ E.\ Dowling}
{1994}
{Dynamic response of Jupiter's atmosphere to the impact of
comet Shoemaker-Levy 9}
{Nature}
{{368}{525}{527}}
{Harrington \etal}
{}
{}
{J.\ Harrington \etal}}
%\comment{Andy's linear wave model}
\def\refikdcslgrl{
{Ingersoll, A.\ P., H.\ Kanamori, and T.\ E.\ Dowling}
{1994}
{Atmospheric gravity waves from the impact of comet P/Shoemaker-Levy 9
with Jupiter}
{Geophys.\ Res.\ Lett.}
{{21}{1083}{1086}}
{Ingersoll \etal}
{}
{}
{A.\ P.\ Ingersoll \etal}}
\begin{document}
\begin{center}
{\bf Evolution of the SL9 Impact Sites and Numerical Experiments\\
with a Two-Layer Rigid-Lid Model}\\[6pt]
\begin{it}
Tadashi Asada \\
Kyushu International University \\[6pt]
Isao Miyazaki \\
Oriental Astronomical Association \\[6pt]
Tokuhide Akabane \\
Hida Observatory\\[6pt]
\end{it}
\end{center}
Ground-based imaging of impact sites of Comet Shoemaker-Levy 9 on Jupiter
was carried out in visible and near infrared wavelength.
Many impact sites were found to be elongated in east-west direction
due to the shear of the zonal flow.
Numerical experiments with two-layer rigid-lid model indicate
that an eddy evoluves to be elongated in east-west direction
by the horizontal shear of the zonal flow
in the case of small Rossby deformation radius,
whereas it survives keeping its circular shape
in the large deformation radius case.
The evolution of impact sites seems to resemble the behavior of the eddy
of small defomation radius.
\newpage
\bc
{\bf IR-Images of Calar Alto:
Investigation of the temporal development of the SL9 impact sites
on Jupiter}\\[6pt]
\bi
Johannes Babion (University Observatory, Munich)\\
Hermann Boehnhardt (University Observatory, Munich)\\
Fionn Murtagh (ST-ECF ESO, Garching)\\
Jean L. Starck (CEA, DSM/DAPNIA, CE-SACLAY, 91191 Gif-sur-Yvette Cedex)\\[6pt]
\ei
\ec
The SL9 impacts at Jupiter were imaged from Calar Alto (Spain) with the
3.5 m telescope + MAGIC Camera in the near infrared and with the
1.2 m telescope + CCD in the visual wavelength range.
After the basic data reduction suitable deconvolution techniques
(Babion et al, European SL9/Jupiter Workshop Proceedings, 1995)
are applied to the images to sharpen the surface structures
of the impact regions on the planet.
Using our time series of multi-wavelength observations the temporal
development of the SL9-impact is assessed.
This still ongoing analysis adresses the rapid expansion during the
initial phase after impact and the long-term diffusion of the ejecta
structures on Jupiter.
In this paper a report on the present status of the project is given and
preliminary results are described.
\np
\begin{center}
{\large \bf Dynamical Evolution of Comet P/Shoemaker--Levy\,9}
\vspace{5pt}
M.E. Bailey$^\ast$, V.V. Emel'yanenko$^\ast$ \& J.V. Scotti$^{\ast\dagger}$
\vspace{5pt}
$^\ast$School of Computing and Mathematical Sciences, Liverpool
John Moores University, Byrom Street, Liverpool L3 3AF, England.\\
$^\dagger$Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona
85721, USA\\
\end{center}
\vspace{1cm}
We report on both the analytical and numerical investigation of the dynamical
evolution of P/Shoemaker-Levy\,9. Secular perturbations on objects in
temporary-satellite-capture (TSC) orbits about Jupiter cause frequent evolution
on to orbits that allow tidal disruption or collision with the planet. The
effect is analogous to the Sun-grazing phenomenon amongst high-inclination
Halley-type orbits about the Sun, and it produces a much higher
Jupiter-collision rate than that expected from a random encounter model.
The order of magnitude of the collision rate is the probability ($\sim\!
10^{-1}$) for a long-lived TSC object to evolve into a Jupiter-grazing or
Jupiter-colliding end-state by secular perturbations, multiplied by the rate of
production of such TSC events per observable Jupiter-family comet per year
($\sim \! 2\times 10^{-4}$). Secular theory and direct numerical integrations
show that the fragments of P/Shoemaker-Levy\,9 passed through a previous
extremely close encounter with Jupiter in 1970, suggesting that the progenitor
must also have made a close approach to Jupiter around this time. We discuss
the similarity between this dynamical evolution and that found for variational
orbits based on P/Gehrels\,3 and P/Helin-Roman-Crocket. Remarkably,
P/Gehrels\,3 was also within the Roche radius of Jupiter at the same time as
P/Shoemaker-Levy\,9 in 1970. Backward integrations of test particles with
initial orbits similar to those of the P/Shoemaker-Levy\,9 fragments are used
to investigate the distribution of possible source orbits for the progenitor of
P/Shoemaker-Levy\,9.
\np
\bc
{\bf Far-ultraviolet emissions from the impact sites of comet
\mbox{P/Shoemaker-Levy 9}\\
with Jupiter}\\[6pt]
\bi
G.E. Ballester(1), W.M. Harris(1), G.R. Gladstone(2), J.T. Clarke(1),\\
R. Prange(3), C. Emerich(3), A. Talavera(4), S.A. Budzien(5),\\
P.D. Feldman(6), M.R. Combi(1), T.A. Livengood(7), M.B. Vincent(1),\\
M.A. McGrath(8), D.T. Hall(6), D.F. Strobel(6), J.M. Ajello(9),\\
L. ben Jaffel(10), D. Rego(1), G.F. Fireman(11), K.L. Jessup(1),\\
L. Woodney(12), S. Miller(13), and X. Liu(9)\\[6pt]
\ei
\ec
\bi
(1) U. of Michigan, (2) Southwest Res. Inst.,\\
(3) Inst. d'Astrophysique Spatiale, France, (4) IUE-VILSPA, Spain\\
(5) Naval Res. Lab., (6) Johns Hopkins U., (7) Goddard Space Flight Center\\
(8) STScI, (9) Jet Propulsion Lab.\\
(10) Inst. d'Astrophysique de Paris, France, (11) Computer Sciences Corp.\\
(12) U. of Maryland, (13) U. College London, UK\\[6pt]
\ei
Observations with the International Ultraviolet Explorer (IUE) during
the collisions of fragments of comet P/Shoemaker-Levy 9 with Jupiter
show far-ultraviolet emissions from the impact sites within a ~20
minute period centered around impact time. Positive detections of H2
Lyman- and Werner-band (1230-1620 A), H-Ly a, C 1657 A, and possibly
Al+ 1671 A emissions were made for the K and S fragment impacts.
Energies of at least 10(21) ergs were emitted at these wavelengths,
corresponding to brightnesses of at least a few hundred
kilo-Rayleighs. No thermal far-UV continuum was detected. The H2
spectrum is consistent with electron collisional excitation if
significant CH4 absorption is included. Such emissions could result
from magnetospheric and/or ionospheric plasma processes generated by
the energetic impacts, and possibly related to the far-UV emissions
imaged 40-50 minutes after the K impact with HST. In this emission
process, the hydrogen could be atmospheric while the C and Al+ would
have to be of cometary origin, and the CH4 absorption could be easily
explained by a stratospheric column in the line-of-sight. Another type
of emission process involves resonant and fluorescent scattering of
continuum thermal radiation by upper atmospheric hydrogen and ablated
comet material. The hot thermal far-UV radiation could have been
produced by either the later stage of the fragment entry, when reaching
sufficiently high pressure levels where the shock may have reached very
high temperatures, and/or also by the early fireball which may have
reached temperatures above ~3500 K when at low altitudes and behind the
limb (cooling to below ~1800 K when directly observable from Earth).
Only small quantities of cometary C and the possible Al+ would be
needed for this emission process. The plausibility of this process
depends on the shape of the H2 spectrum, which has not been modeled.
Scattering of sunlight by the rising plume cannot explain the
emissions, except possibly for the Al+ emission, and direct collisional
excitation in the earliest entry stage or non-thermal emission by the
early non-equilibrium entry shock could in principle have contributed
to the emissions.
\newpage
\bc
\vspace*{-1cm}
{\bf 2$\mu$m spectro-photometry of Jovian aerosol clouds -- scattering
opacities, vertical distributions and wind velocities}\\[6pt]
\bi
D. Banfield, P. Gierasch, S. Squyres, \& P. Nicholson (Cornell)\\
B. Conrath (Goddard), and K. Matthews (Caltech)\\[6pt]
\ei
\ec
Spectro-photometric observations of Jupiter at 9 wavelengths in the
2.0 -- 2.35 micron band were taken on the 5m Hale telescope at Palomar
during the 2 months following the impact of comet P/Shoemaker-Levy 9.
From these, spectra of the discernable spots were measured as they
evolved through this time. Spectra of 4 regions (South Polar Region, North
Equatorial Zone, South Equatorial Zone and Great Red Spot) unaffected
by the comet impacts were also measured.
%
A technique with which near-infrared reflection spectra can be inverted
to yield vertical profiles of scatterer density is presented. For the
wavelengths and bandwidths measured in this study, the sensitivity of
the inversions extends from near 1 bar up to about 15mbar. This
technique was used to estimate the height and total scattering opacity
of the measured comet impact clouds, with the result that all comet
impact clouds were found to lie near or above the vertical limit of our
sensitivity, 15mbar. The lower limit of the clouds is around 50mbar.
%
The total scattering opacity of all of the clouds is seen to decrease
by a factor near 1.7 over the 35 days spanned by the observations.
This is consistent with a change in the mean particle size, with a
general fall-out of some of the cloud material, and with a horizontal
dispersion of clouds. West {\it et al.} (1995) suggest that the mean
particle radius does increase over this time. We have not measured the
horizontal dispersion of the clouds over this time period, and thus
cannot yet separate out the three possible effects to examine particle
fall-out rates.
%
The speeds of stratospheric winds experienced by these clouds were also
measured by two different techniques. The first assumed an {\it a
priori} latitudinal profile for the stratospheric winds (the
tropospheric winds of Limaye (1986)) which was then scaled down. The
scaling factors were chosen to deform early images of the clouds so
that they best matched later images of the same clouds. The second
technique imposed no {\it a priori} assumptions on the wind field, but
rather measured it via a technique similar to that used in
Limaye(1986). Early and later images were correlated with each other
as a function of longitudinal shift for each latitude, yielding zonal
velocities given by the shift of maximum correlation. Both techniques
indicate wind speeds of order -5--15m/s ($\sim 1/2$ those measured by
Voyager in this region).
%
The spectra of the unaffected regions of Jupiter are a very useful
by-product of this data set. They can be used to verify calibrations,
as well as to quantify the vertical distribution of aerosols in
undisturbed regions. For the South Polar Region, we find a
distribution of aerosols (total scattering optical depth $\sim 0.05$)
peaking at about 25mbar, and extending down to near 100mbar. We are
not sensitive to its top limit. The North and South Equatorial Zones
show what appears to be a diffuse aerosol cloud (total scattering
optical depth $\sim 2\times10^{-3}$) near or above the vertical limit
of our sensitivity, overlying a perhaps higher tropopausal cloud deck
at around 450mbar. The South Equatorial Zone shows more variability
than the North. The Great Red Spot shows only a tropopausal cloud
which is again slightly elevated compared to the rest of the planet,
peaking at about 400mbar. Our reflectance spectra inversion technique
can also be applied to other regions of the planet to investigate the
distribution of aerosols there as well.
\np
\bc
{\bf On the Orbital Evolution and Origin of Comet Shoemaker-Levy 9}\\[6pt]
\bi
L.A.M. Benner and William B. McKinnon\\
Dept. Earth and Planetary Sci. and McDonnell Center for the Space Sci.\\ Washington University\\
Saint Louis, MO 63130\\
(e-mail: mckinnon@wunder.wustl.edu)\\[6pt]
\ei
\ec
Based on our dynamical study (submitted for publication), we find that
Shoemaker-Levy 9 (SL-9) orbited Jupiter for most of this century, and
possibly longer, by far the longest known temporary capture by
Jupiter. Secular solar perturbations caused SL-9's inclined and
distant jovicentric orbit to alternate, with a period of $\sim$25 yr,
between intervals of nearly polar inclination (i $\sim 90^{\circ}$) and low
eccentricity and intervals of lower inclination (either prograde or
retrograde) and nearly parabolic eccentricity (e $\approx$ 1.0). This latter
phase brought the comet close enough for disruption on 8 July 1992 and
collision in July 1994. Immediately prior to the 1992 perijove, the
comet passed through Jupiter's tenuous inner ring halo at $1.62 \pm 0.01$
jovian radii, but the population of macroscopic bodies in this portion
of the ring is probably insufficient for collisions to have weakened
the nucleus or disrupted the nucleus. The comet's trajectory was among
the most chaotic of any known solar system body, with an effective
Lyapunov time in jovian orbit of $\sim$10 years. Because of the shortness
of the Lyapunov time compared to the probable length of temporary
capture about Jupiter, SL-9's heliocentric orbit prior to capture can
only be discussed in a statistical sense.
The ensemble of possible pre-capture solutions describe low e and i
orbits just exterior and interior to that of Jupiter. These orbits are
indistinguishable from those of "quasi-Hilda-type" Jupiter-family
comets, a group known to strongly interact with Jupiter and experience
extended temporary satellite captures. Based on their Tisserand
parameters, the orbits are not consistent with a recently escaped
Trojan asteroid, but an origin as such is not impossible.
\np
\begin{center}
{\bf Mid--IR High--resolution Spectroscopy of the SL9 Impact Sites:
Temperature and HCN Retrievals}\\[6pt]
\begin{it}
B.\ B\'ezard (Paris-Meudon Obs.), C.A.\ Griffith (N.~Arizona U.), D.\ Kelly
(U.~Texas), J.\ Lacy (U.~Texas), T.\ Greathouse (N.~Arizona U.), and G.\ Orton
(NASA/JPL)\\[6pt]
\end{it}
\end{center}
We present observations of the SL9 comet's crash that were taken at the NASA
Infrared Telescope Facility (Mauna Kea, Hawaii), with the U.\ Texas
mid--infrared echelle spectrometer IRSHELL. Various impact sites were
imaged at a spatial resolution of 1.5 arcsec and a resolving power of about
15000. Several spectral intervals in the 10--$\mu$m window were observed.
CH$_4$ lines around 1234 cm$^{-1}$ and a C$_2$H$_2$ line near 743 cm$^{-1}$
were observed on July 20, 30 and 31 to monitor stratospheric temperatures
and constrain the analysis of the observed NH$_3$ emission lines (see
poster by Griffith {\it et al.\/}). CH$_4$ line spectra recorded 23 hrs
after impact K and 11 hrs after impact L show enhanced emission over these
sites. This enhancement is very pronounced for the 1233.455--cm$^{-1}$
line but negligible for the $\sim$100 times weaker lines at 1233.147 and
1234.226 cm$^{-1}$, implying that the stratospheric warming was confined
to levels above $\sim$0.2 mbar. We derive temperature enhancements around
45~K for the L impact and 25~K for the K impact at 1~$\mu$bar at the time
of the observations. Mapping of the C$_2$H$_2$ line at 743.265 cm$^{-1}$
indicates a local warming of $\sim$10~K in the 10--$\mu$bar region over
the E site, 2.6 days after impact. HCN emission was detected at 744.458
cm$^{-1}$ over all impact sites observed. The retrieved HCN column
density is somewhat sensitive to assumptions in the gas vertical distribution
and in the temperature profile. A preliminary analysis indicates a column
density of about 10$^{16}$ molec cm$^{-2}$ at the center of the E site 2.6 hrs
after impact, 3 times larger than inferred from millimeter observations
of impact G (Marten {\it et al.\/} 1995).
\newpage
\bc
{\bf Detection of Water in the "Splash" of Fragments G and K of Comet
\mbox{Shoemaker-Levy 9}}\\[6pt]
\bi
G. L. Bjoraker\\
NASA/GSFC\\[6pt]
T. Herter, G. Gull, S. Stolovy, and B. Pirger\\
Cornell University\\[6pt]
\ei
\ec
We observed Jupiter on 17-19 July 1994 using the Kuiper Airborne
Observatory (KAO) deployed out of Melbourne, Australia. The KAO
Echelle Grating Spectrometer uses a Si:As BIB array with 128 spectral
elements at a resolving power of 9000 and 10 spatial elements on
Jupiter. We detected H2O emission lines at 7.7, 22.6, and 23.9
microns. We have obtained temperatures at the peak of the splash phase
for the G and K fragments, for the 3 microbar pressure level. The H2O
lines at 7.7 microns were visible for 10 minutes; those at
23.9 microns were visible for about an hour in G. We have also
obtained column abundances for H2O for both G and K using 7.7 micron
data. Our estimate should be considered a lower limit to H2O as the
7.7 micron data are sensitive only to the portion of water at the
highest temperatures. The G and K fragments exhibited remarkably
similar spectra at the peak of the splash at 7.7 microns. The column
abundance of "hot" H2O at the peak of the splash was roughly
comparable to that of CH4. We interpret the CH4 emission as due to
pre-existing jovian CH4 heated by infalling ejecta. We believe that
the oxygen in the observed H2O is derived from cometary material,
although we cannot distinguish between H2O that may have been formed
through shock chemistry from H2O that may have survived the initial
explosion. A combination of Galileo/NIMS, KAO/HIFOGS, and KAO/KEGS
data favor a scenario in which the fragments did not reach the water
cloud in order to excavate jovian H2O.
\np
\begin{center}
{\bf EFFELSBERG OBSERVATIONS OF JUPITER'S RADIO BRIGHTNESS VARIATIONS
INDUCED BY COMET SHOEMAKER-LEVY 9} \\[6pt]
\bi
M.K. Bird \& \underline{O. Funke}\\
Radioastronomisches Institut\\
Univiversit\"at Bonn\\
Auf dem H\"ugel 71, 53121 Bonn, Germany\\[6pt]
J. Neidh\"ofer\\
Max-Planck-Institut f\"ur Radioastronomie\\
Auf dem H\"ugel 69, 53121 Bonn, Germany)\\[6pt]
I. de Pater\\
Dept.\ of Astronomy\\
University of California\\
Berkeley, CA 91109, U.S.A.\\[6pt]
\ei
\end{center}
As part of a worldwide campaign of Jovian radio observations
associated with the impact of comet SL9,
measurements of Jupiter's flux density and polarization were recorded
for three wavelengths ($\lambda$ = 2.8, 6, 11 cm) at the Effelsberg
100-m Radio Telescope of the Max-Planck-Institut f\"ur Radioastronomie.
The nonthermal flux densities,
attributed to gyrosynchrotron radiation from energetic electrons in the
Jovian radiation belts, are normalized to 4.04 AU and corrected for
the finite size of the emitting region with respect to the beamwidth,
an effect which can be quite important at the higher frequencies.
Two parameter fits were made for each observation day to the Jovian
beaming curve, the radio flux density as a function of
Jupier's rotational phase.
The value of the constant term, the flux density $S_0$,
increased from 4.4 Jy to 5.7 Jy (27\%)
at $\lambda$ = 11 cm and from 2.4 Jy to 3.9 Jy (62\%) at
$\lambda$ = 6 cm during the impact week from July 16 to July 22.
No changes in the radio brightness of 25.6 $\pm$ 0.8 Jy could be
detected at $\lambda$ = 2.8 cm.
The brightness level did not rise uniformly, but was pushed up
preferentially at specific System III longitudes.
Most recent observations in February 1995, more than six months after
the the SL9 collision, indicate that Jupiter's
nonthermal radiation has still not returned to
its pre-impact level.
\np
\bc
{\large\bf{Europe and Io photometry during SL9 fragments impacts}}\\[6pt]
\bi
C. Blanco$^{1}$, G. Leto$^{1,2}$, D. Riccioli$^{1}$\\[6pt]
\ei
\ec
\bi
$^{1}$ Astronomy Institute of Catania University\\
Viale A.Doria 6, I 95125 Catania, Italy\\[6pt]
$^{2}$ Institute of Radioastronomy, VLBI Station\\
C.P. 169, I-96017 Noto (SR), Italy \\[6pt]
\ei
We report on the photometric monitoring of Europa and Io during the impacts
of the comet P/Shoemaker-Levy 9 fragments on Jupiter.
BV photoelectric observations were collected at the Serra
La Nave (SLN) Station of Catania Astrophysical Observatory.
High speed photometry at 0.1~sec and 1~sec integration time was
performed by using the 91-cm Cassegrain telescope equipped with a photon
counting photometer provided by a cooled photomultiplier.
Constraints due to SLN geographical position
have limited our observations to 3 impact events (A, H, Q family). For A and Q
events we have recorded, for Europa and Io respectively, light brightning
exceeding two sigma. The times of the events, their duration and the energy
budget are given and discussed in the light of other observer results.
\np
\bc
{\bf Radiation study of two very bright terrestrial bolides}\\[6pt]
\begin{it}
J. Borovi\v cka and P. Spurn\'y \\
Astronomical Institute, 251 65 Ond\v rejov Observatory, Czech Republic \\[6pt]
\end{it}
\end{center}
For the comparison with the entry phase of the SL-9 collision
with Jupiter, light curves and spectra of two of the brightest photographed
bolides were studied. The \v Sumava bolide (EN\,041274) reached $-21$ absolute
(i.e.\ 100~km distance) magnitude. This fragile cometary body of the initial
mass of about 5000~kg exhibited
many flares and disappeared at the height of 59~km above surface.
The light curve can be explained assuming that the body experienced at least
five subsequent sudden breakups, losing from 25\% to 99\% of its
instantaneous mass in each breakup.
The Bene\v sov bolide (EN\,070591, maximal magnitude $-20$) was a stony body
of the initial mass of about 13\,000~kg which radiated down to 17~km of height
and exhibited bright flare at 24~km. Several fragmentation events
occurred below 42~km of height and are directly visible on the photographs.
In both cases the spectra are composed of emission lines of the vaporized
material. In addition, molecular bands are strong in Bene\v sov.
\np
\bc
{\bf Near-Infrared Spectroscopy of the Shoemaker-Levy 9 Impact Sites with UKIRT: CO Emission from the L Site}
\medskip
\bi
T.Y. Brooke, G.S. Orton, D. Crisp, A.J. Friedson(JPL/Caltech), G. Bjoraker(Goddard)
\ei
\ec
\medskip
Spectra of impact sites in select regions in the 3-5 $\mu$m range were
obtained with the CGS4 spectrometer at the United Kingdom Infrared
Telescope atop Mauna Kea, Hawaii on July 19, 20, 26, 28 UT 1994,
generally long after actual impact. These are being used to determine
the depth of impact effects in Jupiter's atmosphere.
CO emission in the 4.7 micron fundamental vibrational band was
detected at the L site on Jul 20 from 2:20-3:30 UT, over 4 hours after
impact. Lines observed in emission were P4-P6 and R11-R13.
Phosphine and CH$_3$D were not seen in emission. Modelling is in
progress to determine CO abundances at the L site.
\np
\bc
{\bf Limits on Polar Ionospheric Changes during the SL9 Impacts}\\[6pt]
\bi
Michael E. Brown\\
Lunar and Planetary Laboratory\\[6pt]
\ei
\ec
Proposed explanations for many of the auroral and magnetospheric
effects thought to be observed as a consequence of the SL9 impacts
rely on a changes in polar ionospheric conductivity to transmit
the effects through the magnetosphere.
Observations of the Io plasma torus
rotation velocity, which is controlled by this
ionospheric conductivity,
show that no such changes took place during the time of
the impacts. The Lick Observatory observations span a three week interval
centered on the impacts and reproduce 8-months of
data obtained in 1991/1992. Upper limits on daily changes
in the ionospheric conductivity will be presented.
\np
\bc
{\bf Global Imaging Campaign of Shoemaker-Levy 9 Impact Phenomena}\\[6pt]
\bi
M. W. Buie, L. H. Wasserman, R. L. Millis (Lowell Obs.),\\
W. B. Hubbard (U. Ariz.),
H. L. Reitsema (Ball Aerospace and U. Ariz.),\\
F. Roques (Paris Obs.),
A. Peyrot, M. Vignand (Obs. of Les Makes),\\
E. Dunham, C. Ford (NASA/Ames),\\
H. Hammel, J. Faust (MIT),\\
K. Meech, B. Patten (U. Hawaii),\\
J. Bell, III, (Cornell), D. Toublanc (Obs. Bordeaux),\\
R. Thompson (U. Wyoming)\\[6pt]
\ei
\ec
We deployed imaging systems to five sites for the time of the Comet
Shoemaker-Levy 9 impacts on Jupiter. All sites used a combination of
a high-speed optical CCD system with similar broad and narrow-band
filters.
Our coordinated effort covers from a few days prior to the first impact
to up to five days after the last impact. Most of the data consists
of multi-spectral imaging that monitors the morphology and development
of the Jovian atmosphere as the impact week progressed.
Other high-speed ($\sim$8 Hz) imaging sequences were taken from most sites
at the time of impact to search for transient phenomena related to the
impact. Some plumes were recorded through the 8900\AA\
methane-band filter but most high-speed sequences showed no changes.
We will present a summary of the dataset as well as quantified searches for
satellite flashes and other limits on plume phenomena.
\np
\bc
{\bf GALILEO INFRARED OBSERVATIONS OF THE SHOEMAKER-LEVY 9 G AND R FIREBALLS
AND SPLASH}\\[6pt]
\bi
R.W. Carlson, P.R. Weissman, J. Hui, M. Segura, W.D. Smythe,\\
K.H. Baines and T.V. Johnson\\
Jet Propulsion Laboratory\\[6pt]
P. Drossart and T. Encrenaz\\
DESPA, Observatoire de Paris\\[6pt]
F. Leader and R. Mehlman\\
Institute of Geophysics, UCLA\\[6pt]
\ei
\ec
The Galileo spacecraft was fortuitously situated for a direct view of the
impacts of comet Shoemaker-Levy 9 in Jupiters atmosphere and measurements were
recorded by the Near Infrared Mapping Spectrometer (NIMS) instrument for
several of the impact events. Seventeen discrete wavelength channels were used
between 0.7 to 5.0 microns, obtained with a time resolution of 5 seconds. Two
phases of the impact phenomona are found in the data: the initial fireball,
which was evident for one minute, and subsequent fallback of impact ejecta onto
the atmosphere, starting six minutes after fireball initiation.
Preliminary analysis of the G event data shows a fireball appearing at 07:33:37
UT (as would be observed from the Earth) with a temperature of 4000 K or
greater and an effective source diameter of 20 km or less. These spectra show
absorption by methane and molecular hydrogen whose strength place the fireball
in the upper troposphere, above the ammonia clouds. As time progresses, the
fireball cools and the effective diameter increases about 2 km/sec. The
strength of the hydrogen and methane absorption decreases with time, indicating
that the radiating surface is rising supersonically. The fireball appears to
expand adiabatically, with an adiabatic index of 1.2. After about 30 seconds,
the spectra indicate a multiple temperature or opacity structure.
A second phase of strong IR emission for the G event was detected beginning at
07:39:41 UT, which we interpret as impact ejecta, supersonically ejected in the
fireball and plume, falling back upon the atmosphere. The resulting infrared
emission steadily brightened over 2 minutes following its first detection. The
timing of the event implies a minimum ejection velocity of 4 km/sec. Spectra
of this splash phase suggest O-H and C-H stretch emission, perhaps from
shock heated water vapor and methane.
The R impact data show qualitatively similiar behavior, but with intensities
reduced by a factor of two to four.
\np
\begin{center}
\begin{large}
{\bf Absolute Reflectivity Spectra of Jupiter: 0.255 - 4.0$\mu$m}\\[6pt]
\end{large}
\bi
Chanover, N.J., Beebe, R., and Simon, A.\\
New Mexico State University\\[6pt]
\ei
\end{center}
Imaging data from the Hubble Space Telescope (HST) and several ground based
observatories are used to define a reference absolute reflectivity (I/F)
spectrum of Jupiter for all latitudes. The impact of Comet Shoemaker-Levy 9
(SL9) with Jupiter in July 1994 has resulted in a tremendous amount of imaging
data, primarily in the near-ultraviolet to near-infrared wavelength regime.
While these new data sets undoubtedly contain vast quantities of
information about Jupiter's atmosphere and its response to the comet fragment
impacts, they were all obtained from different telescopes, using different
instruments, by different investigators. Consequently, the calibration of all
the data sets is not uniform. This makes comparisons between data sets
difficult, if not impossible. We have used high-resolution SL9 Impact
Campaign data from HST from 0.255 to 0.953 $\mu$m, along with near-infrared
imaging data taken at the Apache Point Observatory, Palomar Observatory,
and the Infrared Telescope Facility in July 1994, to create a reference
spectrum of I/F as a function of wavelength for all latitudes along the
``undisturbed'' central meridian of Jupiter. This spectrum will be made
available to all other SL9 investigators as a tool with which they may
calibrate their own data. An example of how this I/F spectrum can be used
as a calibration tool will be illustrated with February 1995 near-infrared
imaging data taken at Apache Point.
\np
\begin{center}
{\bf Galileo Direct Imaging of Impacts K, N, and W}\\[6pt]
\begin{it}
Clark R. Chapman and William J. Merline\\
Planetary Science Institute\\
Tucson, AZ USA\\[6pt]
Kenneth Klaasen, Torrence Johnson, and
Catherine Heffernan\\
Jet Propulsion Laboratory\\
Pasadena, CA USA\\[6pt]
Michael J. S. Belton\\
NOAO\\
Tucson, AZ USA\\[6pt]
Andrew Ingersoll\\
California Institute of Technology\\
Pasadena, CA USA\\[6pt]
The Galileo Imaging Team\\[6pt]
\end{it}
\end{center}
The Galileo camera obtained direct imaging data of the actual
impact sites, showing the luminous phenomena of bolide entry and
early fireball development for S-L 9 fragments K and N (using a drift
scanning mode) and for W (using time-lapse imaging). All three
bolides -- several-second-long initial flashes -- were of comparable
brightness (a few percent of total Jupiter). But the K event showed a
much brighter and longer-lasting fireball (also, possibly, a second
bolide 10 seconds after the first) than did the other two events,
generally consistent with the relative prominence of subsequent
plume phenomena observed from Earth. Later plume development
for K and W was near or below our detection limits, as were any
secondary impacts during the intervals for which we returned data
(with the exception of the possible second, bright K event). We will
present our latest lightcurves, calibrated brightnesses, and compari-
sons with groundbased data for these events.
These Galileo data provide an excellent baseline for assessing
Earthbased observations of early phases of other S-L 9 impacts that
were observed indirectly. In general, we are confident that the onset
of the luminous event we see is the bolide phase, and that precursor
events seen from Earth cannot be. Precursor events must generally
be either the impact of coma or much smaller, secondary projectiles
(too faint to be seen by Galileo) in Jupiter's uppermost atmosphere.
\newpage
\begin{center}
{\bf A Search for Small-Sized S-L 9 Impactors using a\\
Continuous-Readout CCD}\\[6pt]
\begin{it}
Clark~R.~Chapman, Carol~Neese, William~J.~Merline, Gail~Schneller,
Stuart~J.~Weidenschilling, and Don~R.~Davis\\
Planetary Science Institute\\
Tucson, AZ USA\\[6pt]
Philip Massey\\
NOAO\\
Tucson, AZ USA\\[6pt]
\end{it}
\end{center}
We have performed sensitive observations of the Galilean satellites and
Jupiter's morning limb to search for flashes of bolides by small,
unnamed fragments of comet Shoe\-maker-Levy 9. To make the observations,
we developed a technique of continuously reading the CCD under a mask
that covered all but Jupiter's equatorial plane. Continuous readout
allows high duty cycle and time resolution, while the mask prevents
buildup of unwanted scattered- and sky-light. We cover Jupiter itself
with a tiny neutral density filter. This avoids saturation of Jupiter
as we clock the chip at a rate slow enough to yield adequate S/N per
line on the satellites. Thus, we were able to observe Jupiter and the
satellites simultaneously. The CCD is rotated such that the clocking
direction is tangent to Jupiter at the impact site
($45^{\circ}$ \thinspace S). In this
way, the charge from the streaked Jupiter does not overwrite the impact
site, which is just off the terminator. The resultant images are long
trails of Jupiter and the satellites. Scans are 2~to~17~minutes in length,
with time resolution of 25\thinspace ms per CCD line. Observations were primarily
done using a B filter, which we expected would give us the most sensitivity
to the hot bolide phase of the impacts.
The data were obtained on 8~nights at the Kitt Peak 2.1\thinspace m,
including 3~nights before and during the major impacts, and 5~nights afterwards
(July~16, 17, 21, 27, 28, 29, 30, 31~UT). We attempted to observe during
impacts of fragments B and V. We encountered some problems due to
idiosyncrasies with the modified instrumentation, but we were most
affected by poor weather. We obtained data during approximately 10\% of
our scheduled time. Preliminary analysis shows no obvious impacts,
although we may have observed the V flash. Statistically meaningful
statements about smaller fragments must await more detailed analysis of
the data.
\np
\begin{center}
{\bf Peculiarities of Spectral Evolution of SL9 Secondary Nuclei
Impact Sites on Jupiter}\\[6pt]
\begin{it}
Churyumov K.I., Tarashchuk V.P.\\
Astronomical Observatory of Kiev University, Ukraine\\[6pt]
Prokof'eva V.V.\\
Crimean Astrophysical Observatory, Ukraine\\[6pt]
\end{it}
\end{center}
Spectral observations of Jupiter were conducted at the
Crimean Astrophysical Observatory from July 2 to Aug. 30, 1994.
Altogether $\sim$2000 spectra were obtained.
The impacts of large fragments in the Jupiter atmosphere
caused powerful outbursts that led to complete evaporation of a
penetrated body as well as to heating of the surrounding
atmosphere . Because the comet fragment was surrounded by
a coma that comprised products of evaporation of the cometary
matter and dust, then the region of penetration of cometary
matter in the atmosphere occupied much more space, than the
place of the outburst and heating. Thus in the impact sites
there had to be luminosity of the evaporated cometary matter as
the result of the outburst yielding spectral lines that are
absent in the Jupiter spectrum, and the spectrum of the
atmosphere itself had to undergo changes. The second effect of
the penetration of the fragment surrounded by the
atmosphere could be appearance of certain emissions not only in
the site of the impact but at substantial distances from it as
well. Analysis of the spectra obtained in the Crimean
Astrophysical Observatory allowed to detect a number of
peculiarities in the sites that appeared after the fall down of
cometary fragments in the form of dark spots. Spectral
variability on temporal scales of tens of seconds was
registered in the sites of the impacts of the comet fragments
1 or 2 revolutions of Jupiter later after the impact moments
in the atomic lines and molecular bands of the Jupiter
atmosphere (NH3 , CH4 , H2 and H). Intensities of the lines
and bands also showed changes from spot to spot . Thus in the
spot spectrum that was caused by the fragment A impact
observed 2.2 revolutions of Jupiter , the biggest variability
occurred in the region of the CH4 band. Variability in the
region of quadruple line of molecule H2 was registered when
the impact site from fragment H crossed the central meridian
of Jupiter after 1.3 revolutions of the latter. Repeated
variability in the region of resonance line of Na at 589-589.6
nm as well as in the region of the band of NH3 was
registered several times. Occasionally variability in the
lines of Li at 670.8 nm, Ca at 643.9 nm and H2 at 656.3 nm
occurred. Successive in time occurrence of variability
in different ranges of the spectrum are observed. And all
this allows to suggest stratification of outburst
products and different excitation temperatures that gives
the basis for seeking possible regularities. Variability of
Na with a big Doppler shift that was observed in several
cases is evidence of a complex picture of moving matter in
the new spots. Preliminary estimations of velocities of some
jets of matter gave the value 300-600-1000 km/sec, here
the velocity vector had the direction both along the ray of
the sight and in the opposite direction.
\newpage
\bc
{\bf Hubble Space telescope Far-Ultraviolet Imaging of Jupiter
During the Impacts of Comet Shoemaker-Levy~9}\\[6pt]
\bi
John T. Clarke(1), Renee Prange(2), Gilda Ballester(1), John Trauger(3),\\
Robin Evans(3), Karl Stapelfeldt(3), and Wing Ip(4)\\[6pt]
\ei
\ec
\bi
(1) University of Michigan\\
(2) CNRS - Universite de Paris, Orsay\\
(3) Jet Propulsion Laboratory\\
(4) Max Planck Institut fur Aeronomie\\[6pt]
\ei
Hubble Space Telescope far-ultraviolet images of Jupiter during the
Shoemaker-Levy 9 impacts show the impact regions darkening over 2-3 hours
post-impact and darker and more extended than at longer wavelengths, indicating
UV-absorbing gases or aerosols more extended, more absorbing, and at higher
altitudes than the visible absorbers. Transient auroral emissions were
observed near the magnetic conjugate point of the K impact site just after
that impact. The global auroral activity was fainter than average during
the impacts, while a variable auroral emission feature was observed inside
the southern auroral oval preceding the Q1/Q2 impacts.
\np
\begin{center}
{\Large\bf An Update on Imaging Observations from McDonald Observatory} \\ [15pt]
\parbox{11cm}{
A.~L.~Cochran, B.~J.~Armosky, C.~E.~Pulliam,
B.~E.~Clark, W.~D.~Cochran, M.~Frueh, D.~F.~Lester, L.~Trafton (U. Texas),
Y.~Kim (U. Maryland), C.~Na (SWRI), W.~Pryor (LASP)}
\end{center}
During and shortly after the impact of SL9 into Jupiter, we obtained
imaging data using the 0.8-m telescope and CCD detector, and 2.7-m
telescope and HgCdTe detector at McDonald Observatory.
We present here further analysis of imaging observations which were obtained
during the impacts. We observed the impact of the R fragment
into Jupiter and present optical and IR light curves.
In addition, we have continued to obtain CCD images of Jupiter since
the impact, including observations in January through March 1995.
We will examine how the impact sites have varied with time.
\newpage
\begin{center}
{\bf High Resolution CCD Spectroscopy of the Comet Shoemaker-Levy~9
Impact Locations on Jupiter}\\[6pt]
\begin{it}
William D. Cochran (University of Texas), Kevin H. Baines (JPL)
Chan Na (SWRI), and Wayne Pryor (LASP)
\end{it}
\end{center}
We used the McDonald Observatory 2.7m telescope 2Dcoud\'e cross-dispersed
echelle spectrograph to obtain high resolution ($R = 60,000$)
spectroscopy of Jupiter over the 4000-10000{\AA} region
during and immediately after the impacts
of the fragments of Comet Shoemaker-Levy~9 on Jupiter.
The spectrograph entrance aperture of $8.2 \times 1.2$\,arcsec allowed
us to obtain spatially resolved spectra of the impact spots and the
surrounding undisturbed regions of the Jovian atmosphere.
We model the observed H$_2$, NH$_3$ and CH$_4$ lines in order to
derive the altitude and optical thickness of the stratospheric haze
caused by the impacts as a function of wavelength and of time.
We also present results of a search for absorption by H$_2$O in the visible
spectrum.
\newpage
\bc
{\bf Jovian Acoustics and Gravity Waves}\\[6pt]
\bi
Michael D. Collins and B. Edward McDonald\\
Naval Research Laboratory, Washington, DC 20375\\[6pt]
W. A. Kuperman\\
Scripps Institution of Oceanography, La Jolla, CA 92093\\[6pt]
William L. Siegmann\\
Rensselaer Polytechnic Institute, Troy, NY 12180\\[6pt]
\ei
\ec
We have modeled the propagation of acoustic and gravity
waves from the impact sites of Comet Shoemaker-Levy 9
using a three-dimensional technique that accounts for
spatial variations in sound speed, BV frequency, density,
and wind velocity. The zonal winds act as horizontal
waveguides that pinch the propagating energy into beams
that remain coherent all the way around Jupiter. Since
the energy in the beams is enhanced by about an order of
magnitude, they indicate the most favorable locations to
look for evidence of waves far from the impact sites.
It has been established that gravity waves appear near the
impact sites in HST images [H. B. Hammel et al., Science
267, 1288-1296 (1995)]. Some of the HST images also
show evidence of an outward moving front that is at a
location consistent with the group speed of an acoustic
wave.
\np
\bc
{\bf Palomar Mid-infrared Spectroscopic Observations of Comet
Shoemaker-Levy 9 Impact Sites}\\[6pt]
\bi
B.J. Conrath\\
NASA/GSFC\\[6pt]
P.J. Gierasch, T. Hayward, C. McGhee,\\
P.D., Nicholson, \& J. Van Cleve\\
Cornell University\\[6pt]
\ei
\ec
Post impact spectra between 8 and 14 micrometers of the
Shoemaker-Levy 9 impact sites and surrounding regions, acquired
with SpectroCam-10 on the Hale telescope, are analyzed. Both direct
modeling and inversion techniques are used to infer information on
Jovian atmospheric composition and thermal structure from these
observations. In the days immediately following the impacts, over
areas with diameters of approximately 2000 km centered on the
sites, stratospheric temperatures are found to be elevated relative to
adjacent, unperturbed areas. A parameterized retrieval of the
vertical distributions of ammonia and phosphene indicate that these
gases are substantially enhanced in the stratosphere, and strong
stratospheric emission from ethylene is also observed. The temporal
behavior of the retrieved atmospheric parameters associated with
sites K and L over a 5-day post impact period is summarized. Stratospheric
aerosol opacity in the 10-micrometer region is presented. Finally,
implications of these results concerning the radiative and dynamical
processes associated with the sites are considered.
\np
\bc
{\bf Near-Infrared Imaging Spectroscopy of the Impacts of
SL9 Fragments C, D, G, K, N, R, V, and W with Jupiter}\\
\bi
D. Crisp (JPL) and V. Meadows (NRC/JPL)\\[6pt]
\ei
\ec
We used the InfraRed Imaging Spectrometer (IRIS) on the
Anglo-Australian Telescope to observe the collisions of 8 of the Comet
Shoemaker-Levy 9 fragments with Jupiter. We also monitored the
evolution of the impact sites from 16 to 23 July, 1994.
Spatially-resolved K--band (1.98--2.38 $\mu$m) spectral image cubes
were collected during the C, D, G, K, R and W impact events. An
H--band (1.4--1.8\,$\mu$m) image cube was also collected during the
Fragment K impact event. Fast-rate 2.35 $\mu$m filter photometry was
used to monitor the impacts of fragments N and V. The IRIS image cubes
provide a spectral resolution of 300 ($\lambda/\Delta\lambda$), a
spatial resolution of 0.6$^{\prime\prime}/$pixel, and a temporal
resolution of $\sim 2$ minutes or less ($\sim 30s$ for fragment K).
These observations therefore provide detailed descriptions of the
impact events, from the time the fragments entered the Jovian
atmosphere, until their collapsed plumes crossed the limb and traversed
the day side of Jupiter. Many of the AAT/IRIS observations were
simultaneous with Galileo or HST observations, facilitating comparisons
among these data sets. Each event was first detected as one or more
faint flashes (precursors). The G and K precursors were first detected
0.5 to 1.5 minutes before the impact fireball was observed by
instruments on the Galileo spacecraft. We acquired spectra of both the
first (entry) precursors, and second (fireball) precursors for
fragments C and K. The first precursors' spectra were dominated by
blue continuum emission. The second precursors' spectra were much
redder, and exhibited enhanced CH$_4$ absorption features at 2.20, 2.32
and 2.70 $\mu$m as they faded. These precursors were followed 5--10
minutes later by a much brighter ``main flash" which peaked 8-15
minutes after the second precursor. The main flashes were also
initially dominated by continuum emission with color temperatures
decreasing from $>$500 to $\sim230$\,K. Weak CO absorption at
wavelengths $>2.3$\,$\mu$m was also occasionally detected during the
initial phase of the main flashes. As the intensities of the main
flashes peaked and started to fade, our spectra revealed strong line
emission by CO ($\lambda > 2.29 \mu$m), NH$_3$ (2.03\,$\mu$m), CH$_4$
(2.20\,$\mu$m) and H$_2$O (2.0 and 2.3\,$\mu$m). H$_2$ (2.122\,$\mu$m)
quadrupole emission was also detected during the decay of the the C and
D flashes. The CO line emission indicated rotational temperatures
$>2000$\,K. Thirty minutes after each impact, there was little or no
evidence of CO, H$_2$, or H$_2$O absorption and emission in our
spectra of the impact clouds.
The initial dominance of continuum emission over line emission in the
main infrared flashes suggests emission from hot particulates rather
than gases in the rising impact plume. CO seen in absorption in the
initial phases of the main flash may have been transported upwards in
the expanding, cooling, fireball. The hot CO, NH$_3$ and H$_2$O seen
during the decay of the main flash are indicative of a `splashback'
event as the plume collapsed. Emission rates, and an estimate of the
total abundance of emitting molecules will be presented. A radiative
transfer model was also used to estimate the altitude and particle
properties of the impact clouds. The spectra of the impact sites
several hours after impact can be simulated by an optically-thin
($\tau$\,$>$\,0.25) cloud consisting of small
($\sim$\,0.25\,$\mu$m),reflective ($\omega$\,$>$\,$0.97$) particles,
located above the 1\,mbar level.
\np
\bc
{\bf THE R-IMPACT: FLASHES AND FIREBALLS, WHAT DID WE SEE?}\\[6pt]
\bi
Imke de Pater, P. Nicholson, K. Zahnle, J. R. Graham, G. Jernigan,\\
T. Hayward, G. Neugebauer, K. Matthews, A. Weinberger,\\
M. Liu, M. Brown\\[6pt]
\ei
\ec
The R-impact was observed at 2.3, 3.2 and 4.5 $\mu$m with the Keck and
Palomar telescopes respectively. We will show a comparison of the
various datasets, and compare the event times with the timing of the
flashes observed by the Galileo spacecraft. Based upon the viewing
geometry and timing of the various events, we suggest the following
quantitative scenario for the sequence of events. Given the timing of
{\it Flash 1}, it must be related to the comet's entry into Jupiter's
atmosphere. The time evolution of the flash is very similar at the
three wavelengths; it lasts for about 40 seconds and the flux ratios
are consistent with a temperature of $\sim 1000$ K. We suggest it is
the meteor trail seen about 400 km above Jupiter's cloud deck. The
duration of the trail is indicative of the
cooling time of the heated trail high up in the atmosphere, or
it may suggest the comet fragment to be broken up into a
string of material about 2000 km in extent.
{\it Flash 2}, starting approximately one minute
after the first flash appeared, has a rapid rise time at all three
wavelengths. This flash is roughly 20 times brighter at 4.5 $\mu$m
than at 2.3 $\mu$m. We attribute the second flash to thermal emission
from the fireball rising above the limb of Jupiter. The decay,
presumably indicative of adiabatic cooling, is slow at 2.3 $\mu$m
($\sim$ 3 min), but quite fast at 4.5 $\mu$m ($\sim$ 30 sec). This is
just opposite to what one would expect for a slowly cooling fireball,
and is not yet explained. Galileo saw its first flash $\sim15$
seconds before Keck and Palomar saw the second flash. Since Galileo
NIMS had a direct view of the impact site, it was able to see the
fireball well before Earth-based observers.
The evolution of the third and brightest {\it flare} is similar at all
three wavelengths. We attribute this flare to a high atmospheric
temperature ($T\approx 600$ K) induced by the release of gravitational
potential energy by fireball material raining down onto the
atmosphere. The beginning of the flare was also seen by Galileo. A
fourth peak seen 10 min after the main flare is similar to those
reported from the H and L impacts. At optical wavelengths, HST
observed several plumes (A, E, G and W) in reflected sunlight.
Although the infrared flares and HST plumes are generally seen at the
same time, we believe that they represent different aspects of the
same elephant.
\np
\bc
{\bf THE OUTBURST OF JUPITER'S SYNCHROTRON RADIATION FOLLOWING\\
THE IMPACT OF COMET P/SHOEMAKER-LEVY 9}\\[6pt]
\bi
Imke de Pater, C. Heiles, M. Wong, F. van der Tak, R. Millan (UCBerkeley),\\
R.J. Maddalena (NRAO Green Bank) M.K. Bird, O. Funke (Univ. of Bonn),\\
J. Neidhoefer (MPI Bonn), R. M. Price, M. Kesteven (CSIRO, Australia),\\
M.J. Klein, S.J. Bolton (JPL), R.S. Foster (NRL),\\
S. Sukumar (DRAO,Penticton), R.G. Strom (NFRA, Dwingeloo),\\
R.S. LePoole (Leiden Univ., Netherlands),\\
R.W. Hunstead(Sydney Univ, Australia)\\[6pt]
\ei
\ec
Jupiter's microwave emission was observed since well before the SL9
impact by many different telescopes. We present the total intensity
data at wavelengths between 6 and 90 cm (an improved subset of the data
published by de Pater et al., 1995, submitted to Science, Dec. 1994).
The flux density increased, depending on wavelength, by 10--45\% during
the week of impacts, and the radio spectrum hardened. Following the
week of cometary impacts, the flux density began to subside at all
wavelengths, while the spectrum continued to harden. The flux density
was still declining in February 1995. We suggest that the increase in
flux density is caused by energization of the resident particle
population. The evolution of the radio spectrum after the SL9
encounter may be caused by an enhancement in the amount of
magnetospheric dust, due to the break-up and ``outgassing'' of the
comet. The radio flux density measurements may be the only dataset
sensitive enough to determine the amount of cometary dust injected into
the magnetosphere. As such, the radio data provide a unique probe of
radial diffusion in Jupiter's magnetosphere.
We show the time evolution of the brightness distribution of the radio
emisison as observed by the VLA and the WSRT telescopes. A preliminary
reduction and analysis of the VLA images shows, crudely, the following
phenomena: {\bf a}) The enhancement in Jupiter's flux density is,
initially, dominated by an enhancement in the magnetic equator at
longitudes $\lambda_{III} \approx 160-260^\circ$, in the socalled {\it
active sector}. {\bf b}) There is {\it no} obvious connection with the
impact sites or times. {\bf c}) The radiation peak which brightened is
often (but not necessarily always) displaced inwards, closer to
Jupiter. This suggests that radial diffusion plays some role and that
(part of) the increase in the radio emission can be explained through
electron energization by conservation of the first adiabatic
invariant. {\bf d}) The impact-induced asymmetry between the peaks
lasts for less than 4 days, as expected from the energy dependent drift
period of the energetic particles.
\np
\begin{center}
{\bf Flaring-up Splitting of SL9 after Encounter with Jupiter}\\[6pt]
\begin{it}
E.M. Drobyshevski\\
Ioffe Physico-Technical Inst.\\
194021 St.Petersburg, Russia\\
E-mail: emdrob@drob.pti.spb.su\\[6pt]
\end{it}
\end{center}
Assumption of tidal disruption of SL-9 contradicts numerous data: it
lasted months after the perijove passage, the fragments' velocity
depended on their size, etc. One can hardly explain why this breakup
should be distinguished from rather common breakups of other comets
far from planets. Such breakups are believed to be caused by the inner
energetics of comets and they correlate with a flare comet activity
which, in its turn, is tied somehow with the Solar activity. The inner
energy sources of SL-9 were triggered likely by the same cause that
initiates the sources in comets when they cross sector structure
boundaries in the Solar wind, viz. by electric current flown through
the SL-9 nucleus when it found its way deep into the Jovian
magnetosphere and ~100 kV e.m.f. was induced across the nucleus
(recall that 400 kV e.m.f. induced across Io generates ~5 MA current).
What an energy source is required for: (1) being initiated by the
current, (2) being capable of imparting ~1 m/s velocity to ~1 km
fragments, and (3) being active in them during months? The only option
reported thus far could be the dirty ice saturated with its
electrolysis products and so capable of burning and even detonation
when some additional energy is supplied. This hypothesis is proved to
be fruitful as for numerous minor bodies' origin understanding,
explanation of SP comet energetics and chemistry, including their
distant outbursts etc, and for explanation why in SL-9 fragments and
in plumes originated after their infall onto Jupiter no water traces
were detected. Here water could evaporate due to electrolized ice
outburning before discovery of SL-9 and its hitting Jupiter.
\newpage
\begin{center}
{\bf Lithium Presence in Impact Plume Favors the Planetary
Origin of SL9 }\\[6pt]
\begin{it}
E.M. Drobyshevski\\
Ioffe Physico-Technical Inst.\\
194021 St.Petersburg, Russia\\
E-mail: emdrob@drob.pti.spb.su\\[6pt]
\end{it}
\end{center}
Lithium is one of the less abundant elements. Its detection in SL-9 L
fragment plume has risen a number of questions. Two ones are main: (1)
why was Li observed never before, even it Sun-grazers, and (2) why was
it localized in some portion of the SL-9 ice only? The great localized
Li overabundance can be hardly explained in framework of standard
hypotheses on the primary cometary grains' formation in turbulized
gaseous medium.
The New Eruptive Cosmogony (NEC) of minor bodies considers the SP
comet nuclei to be fragments of icy envelopes of Ganymede-type bodies.
Such ice accumulates its electrolysis products 2H2+O2 as the
solid-state solution. On reaching their ~15-20 wt.% concentration, it
can explode being initiated by the meteoroid impact. The local Li
concentration in comet ice can be understood from the NEC standpoint
if one takes into account geochemical processes occurring inevitably
in parent planetary bodies. These processes involve at first an
igneous concentration of Li in acid and sedimentary rocks of the rocky
core crust and, afterwards, the aqueous washing out and electrolytic
transport of Li compounds into the water-ice mantle. These compounds
are accumulated there in the last salt brine resting after the water
freezing (or evaporation). By this way Li can be accumulated in the
form of separate ore nests near the rocky core surface and in the ice
envelope. Thus, in the context of NEC, it is not surprising that Li
occurs to be concentrated only in a small part of far from all the
cometary nuclei.
\newpage
\centerline {\bf Changes in Flux and Brightness of Jupiter's Synchrotron
Radiation}
\centerline {\bf During and After SL-9 Impacts}
\vskip 5mm
\centerline {\it George A. Dulk$^{1,2}$, Yolande Leblanc$^1$ and Richard W.
Hunstead$^3$}
\medskip
\centerline {$^1$DESPA, Observatoire de Paris, 92195 Meudon, France.}
\centerline {$^2$University of Colorado, Boulder, CO 80309-0391, U.S.A.}
\centerline {$^3$University of Sydney, Sydney, NSW 2006, Australia}
\vskip 5mm
The Australia Telescope and the Molonglo Observatory Synthesis Telescope were
used to observe Jupiter before, during and after the impacts of SL-9.
Integrated flux and 2-D images of Jupiter's synchrotron radiation belts were
produced with a resolution of $4''\times 18''$ at 13~cm, $7''\times 30''$ at
22~cm and $43''\times 200''$ at 36~cm.
Starting about one day after the first impact and reaching a peak soon after
the time of the last impact, the integrated flux density increased by
approximately 30\% at 13~cm, 25\% at 22~cm and 40\% at 36~cm.
Before the impacts, at 22~cm, the images were similar to those observed at
20~cm by the VLA 12 years earlier at the same longitudes. During and after the
SL-9 impacts the belts were brighter than before, and remained bright at least
12~days after the first impact. The increase in brightness was almost entirely
confined to one hemisphere, between about 100$\deg$\ and 240$\deg$\ longitude.
The changes in the belts at 13~cm were similar to those observed at
22~cm. The new asymmetry implies the existence of a new or
newly-accelerated population of relativistic electrons confined to a
portion of the magnetic field of the planet.
\newpage
\bc
{\bf Abundances of NH$_3$ and CS$_2$ and Upper Limits of H$_2$S, PH$_3$,
C$_2$H$_2$, and C$_2$H$_6$ Above the SL9/G Impact Site}\\[6pt]
\bi
S.G. Edgington and S.K. Atreya\\
Department of Atmospheric, Oceanic and Space Sciences\\
University of Michigan, Ann Arbor, MI 48109-2143\\[6pt]
L.M. Trafton
Department of Astronomy\\
University of Texas, Austin, TX, 78712\\[6pt]
J.J. Caldwell\\
Institute for Space and Terrestrial Science\\
Space Astrophysics Lab., 4850 Keele St., North York, ON, M3J 3K1\\[6pt]
K.S. Noll and H.A. Weaver\\
Space Telescope Science Institute\\
3700 San Martin Drive, Baltimore, MD 21218\\[6pt]
\ei
\ec
Two-stream radiative transfer models allowing for
anisotropic scattering were used to fit the July~18, 1994 Hubble
Space Telescope/Faint Object Spectrograph 170--230~nm observations
of Jupiter above the G-impact site. Aerosol unit optical depths
were varied to occur within 0.3--10~mb and the refractive index
was varied to account for a range of possible aerosol materials.
The models yield abundances for NH$_3$ and CS$_2$ of
$(0.25-1.3) \times 10^{16}$~cm$^{-2}$
and $(0.43-1.1) \times 10^{15}$~cm$^{-2}$, respectively, at the unit
optical depth level
in the part of the atmosphere above the G-impact site. The upper
limits of H$_2$S, PH$_3$, C$_2$H$_2$, and C$_6$H$_6$ at the unit
optical depth level are $1.2 \times 10^{16}$~cm$^{-2}$,
$3.3 \times 10^{14}$~cm$^{-2}$,
$1.0 \times 10^{17}$~cm$^{-2}$,
and $3.3 \times 10^{14}$~cm$^{-2}$, respectively.
\np
\begin{center}
{\bf Near-Infrared Spectroscopy of Jupiter at the Time of Comet
\mbox{Shoemaker-Levy 9} Impacts: Emissions of CH$_{\bf 4}$,
H$_{\bf 3}^{\bf +}$ AND H$_{\bf 2}$}\\[6pt]
\begin{it}
Th.Encrenaz and P.Drossart (DESPA, Obs.Paris), R.Schulz and J.A.Stuewe
(MPIA Lindau), G.Wiedemann (ESO, Garching),
and J.Crovisier (ARPEGES, Obs.Paris)\\[6pt]
\end{it}
\end{center}
Near-infrared emissions of the SL9 impact sites of Jupiter have been recorded
on July 16-18, 1994, using the IRSPEC imaging spectrometer at the 3.5m NTT of
ESO (La Silla, Chile). A very strong emission of methane was recorded between
3.50 and 3.56 microns, shortly after impact H, showing evidence for a strong
and temporary increase of the Jovian stratospheric temperature. Emissions of
H2 (2.12 microns) and H3+ (3.53 microns) werew detected above some of the
impact sites, several hours after the impacts. A strong continuum was also
detected at 2.12 microns over the impact sites, presumably due to intense
scattering of reflected sunlight by high-altitude stratospheric haze.
\newpage
\begin{center}
{\bf Infrared Heterodyne Observations of NH$_{\bf 3}$ and
C$_{\bf 2}$H$_{\bf 6}$ After The Collision of
Comet \mbox{P/Shoemaker-Levy 9} With Jupiter}\\[6pt]
\begin{it}
K. E. Fast(UMD), T. Kostiuk(NASA/GSFC), F. Espenak(NASA/GSFC), D. Zipoy(UMD),\\
D. Buhl(NASA/GSFC), T. A. Livengood(UMD), G. Bjoraker(NASA/GSFC),\\
P. Romani(NASA/GSFC), J. Goldstein(SI/NASM)\\[6pt]
\end{it}
\end{center}
Spectra were taken with the Goddard Infrared Heterodyne Spectrometer during
the NASA/IRTF observing campaign of the collision of comet P/Shoemaker-Levy
9 with Jupiter. Stratospheric NH3 emission was observed at a number of
impact regions days after the collisions. The true line shapes, obtainable
with this instrument, indicate NH3 emission from between 1 and 10 mbar at
the impact regions. Stratospheric C2H6 emission was also observed along
the impact latitude. Preliminary analysis and conclusions will be
presented, along with the results of follow-up measurements made in March
'95.
\newpage
\begin{center}
{\bf HST Observations of Mg$^{\bf +}$ and Dust in Outburst \\
from Comet P/Shoemaker-Levy 9}\\[6pt]
\begin{it}
P. D. Feldman (JHU), H. A. Weaver (STScI), D. C. Boice (SWRI),\\
S. A. Stern (SWRI), M. A. McGrath (STScI)\\[6pt]
\end{it}
\end{center}
Ultraviolet spectroscopy of SL9 was performed on three
different occasions between July 1993 and July 1994 (Weaver \etal\ 1994, 1995)
using the Faint Object Spectrograph (FOS) of the
Hubble Space Telescope with the primary objective to search for the hydroxyl
radical (OH) as a tracer of water ice in the SL9 fragments.
Although OH was not detected during these spectroscopic
investigations, strong \Mgtwo\ emission near 2800~\AA\ was observed
in the vicinity of fragment G during a very short outburst on 14 July 1994.
The emission decayed with a time constant of about one minute.
Approximately 18 minutes
after the \magplus\ outburst, the continuum spectrum of dust scattered
sunlight also changed dramatically, increasing
by more than a factor of three over an 8~minute period and then relaxing
back to the quiescent level less than 20 minutes after the start of the
outburst. The enhanced continuum also exhibited a strong reddening,
$\sim$13\% per 100 \AA , compared with a flat solar spectrum for the
quiescent dust.
The two lines in the \Mgtwo\ doublet are
partially resolved in the HST spectrum, indicating that the emission
was strongly peaked within a spatial region of $\sim$1000 km and suggesting
ion sputtering of the dust surrounding the fragment as a possible source
mechanism. This structure also excludes the possibility of the \Mgtwo\
emission arising from a terrestrial atmospheric source.
At the time of these observations the
comet was \mbox{$3.8 \times 10^{6}$ km} away from Jupiter, which is
consistent with the expected location of the magnetopause.
Neutral Mg was not detected, although the strong \Mgone\ resonance transition
at 2853 \AA\ was in our bandpass. Quantitative estimates of the amount
of mass released in these two events and physical constraints on
possible source and loss mechanisms will be presented.\\
References:\\
H. A. Weaver \etal, 1994. {\it Science} {\bf 263}, 787. \\
H. A. Weaver \etal, 1995. {\it Science} {\bf 267}, 1282. \\
\newpage
\begin{center}
{\bf Calibrating groundbased observations of the SL-9 impact clouds
with small telescopes using the HST WFPC2 images as 'ground truth'}\\[6pt]
\begin{it}
Daniel Fischer\\
Planetary and Cometary Observers Group\\
Germany\\[6pt]
Carlos Hernandez\\
Association of Lunar and Planetary Observers\\
U.S.A.\\[6pt]
\end{it}
\end{center}
While the images from the HST have undoubtedly the highest
angular resolution, the temporal coverage of the evolution of the impact
clouds on Jupiter is very uneven and displays large gaps; furthermore, due
to sun proximity concerns no images could be obtained for many months after
late August. In contrast, a tremendous network of dedicated amateur observers
was following the developments on Jupiter almost minute by minute for months,
and it has been suggested that these CCD images and drawings with small
telescopes form a valuable resource for our understanding of both the impact
physics and the wind motions on Jupiter (Limaye, AGU Fall Meeting 1994). We
are comparing archival HST WFPC2 images with simultaneous amateur observations
to determine the precision and general reliability of the latter and to
arrive at rules one should follow in interpreting them.
\newpage
\bc
{\bf Near-IR Spectral Images from WIRO using the U. of Rochester
Array of Jupiter during Comet Shoemaker-Levy 9 Impact Interval}\\[6pt]
\bi
Brendan Fisher, Judith Pipher, William Forrest, \& Eric Howard\\
U. Rochester\\[6pt]
Chick Woodward \& Bob Howell\\
U. of Wyoming\\[6pt]
Bob Gehrz\\
U. of Minnesota\\[6pt]
\ei
\ec
The University of Rochester Infrared group, in collaboration with the
University of Wyoming and the University of Minnesota collected a large
set of near-IR image data of Jupiter in July 1994 from the 2.3-m telescope
at the Wyoming Infrared Telescope Facility using a 256x256 InSb array.
We obtained a large number of images in the 1.6-2.3 and 2.9-4.0 micron bands
with two CVFs with a spectral resolution of 2%. Additionally, the planet
was imaged in the J, H, K, L', and M' (4.67) bands. The B, U, and V
impacts were observed but no effects were seen in the preliminary
analysis. Other sites were observed after the impacts as permitted.
We have observed an unusual spectral emission in the Q1 spot near 3.35
microns during its first transit that was not visible in other spots
visible on the disk at the same time. Other preliminary results and
progress will be presented along with a summary of our spectral-temporal
coverage.
\np
\begin{center}
{\bf Optical spectroscopy of atomic emission from the
L and Q$_1$ impacts on Jupiter}\\[6pt]
\begin{it}
A. Fitzsimmons, J. E. Little \\
Queen's University of Belfast \\
Belfast, UK\\[6pt]
P.J.Andrews, R.Catchpole, N.Walton \\
Royal Greenwich Observatory \\
Cambridge, UK \\[6pt]
I.P.Williams \\
Queen Mary \& Westfield College\\
London, UK\\[6pt]
\end{it}
\end{center}
During the impacts of fragments L we observed the associated
low-resolution optical spectrum at wavelengths 350nm-670nm.
The spectra demonstrate the existence
of neutral Na, Fe, Mg, Ca and Mn in the plume, which we identify as
remnants of the vapourised bolide. The following night we also obtained
high-resolution spectra of Na D doublet emission resulting from
the impact of fragment Q1. We have constructed models that are able
to explain the observed emission line intensities. We will present our
latest modelling of the temperatures and column densities
of the various atomic species observed.
\np
\bc
{\bf Model Calculations of Aerosol Particle Mean Radius and Number Density
Formed in Comet SL-9 Fireballs}\\[6pt]
\bi
A.J. Friedson, R.A. West, and K.H. Baines\\
JPL/Caltech\\[6pt]
\ei
\ec
We present calculations of the mean radius and number density of
particles condensing in a fireball expanding along a moist adiabat, for
various assumed compositions for the aerosol. The initial mass of
condensible vapor in the fireball is an important parameter.
Relatively volatile species such as ammoniatend to form particles less
than a few tenths of a micrometer in radius; refractory species
generally produce particle radii greater than 1 micrometer. We
estimate the optical depth of plumes seen above Jupiter's limb at
visible and near-IR wavelengths for different cases of composition and
vapor mixing ratio.
\np
\begin{center}
\LARGE
Long Term Monitoring of Jupiter's Synchrotron Radiation with the
Nan\c{c}ay Radiotelescope at the Time of the Collision with Comet
P/Shoemaker-Levy 9
\vspace{1cm} \\
\large
Patrick H. M. GALOPEAU, Eric GERARD \\
and Alain LECACHEUX
\vspace{1cm} \\
Observatoire de Paris, URA CNRS 1757 \\
5, Place Jules Janssen, F-92195 Meudon Principal Cedex, France
\vspace{2cm}
\end{center}
The jovian synchrotron emission has been monitored with the Nan\c{c}ay
radiotelescope at 1410 MHz, 1666 MHz and 3300 MHz from 1 April 1994 to 23
February 1995. Between 13 July and 26 July 1994, we have observed a 20 \%
increase of the non-thermal flux at 1410 and 1666 MHz but a 40 \% increase at
3300 MHz. In February 1995, the non-thermal fluxes at the three frequencies are
still 50 \% above the pre-encounter levels. There is no significant change of
the beaming curve during the pre- and post collision periods. The possibility
of changes in the degree of linear polarization and source size are
investigated.
\newpage
\begin{center}
{\bf Multi-Filter Optical Observations of SL9 Impact Spots on Jupiter}\\[6pt]
\begin{it}
Galen Gisler\\
Los Alamos National Laboratory\\[6pt]
Bryan Laubscher\\
Amparo Corporation\\[6pt]
Nancy Chabot\\
Los Alamos National Laboratory\\[6pt]
Kirsten Boudreaux and Randy Grashuis\\
University of New Mexico\\[6pt]
\end{it}
\end{center}
The 24-inch telescope of the Capilla Peak Observatory of the University of
New Mexico was used to observe Jupiter during the week of the impact of
comet Shoemaker-Levy-9 onto Jupiter. Images of Jupiter were obtained in
several narrow-band interference filters. The opacity in the spots is
calculated as a function of wavelength, and used to infer the distribution
of the debris with altitude. The debris is found to reside very high in the
aerosol layer above the visible cloudtops.
\newpage
\bc
{\bf IRTF Impact Imaging Results}\\[6pt]
\bi
J. D. Goguen, A. J. Friedson, G. S. Orton\\
JPL\\[6pt]
The IRTF Science Team\\[6pt]
\ei
\ec
Highlights of the IRTF results are published in the special issues
of {\it Science\/} and {\it Geophysical Research Letters}. This poster
will include some of those highlights pertaining to impact imaging
of precursors and plume evolution, but will focus on aspects of the impact
data set not previously reported. The IRTF acquired useful data for the B,
C, F, G, and R impacts.
\np
\bc
{\bf Mid-IR Spectroscopy and NH$_3$ and HCN Images of K Impact Site}\\[6pt]
\bi
C.A. Griffith (N.~Arizona~U.), B. B\'ezard (Paris-Meudon Obs.), D. Kelly (U.~Texas),\\
J. Lacy (U.~Texas), T. Greathouse (N.~Arizona~U.), \& G. Orton (NASA/JPL)\\[6pt]
\ei
\ec
We present observations of SL9 comet's crash that were taken at the
NASA Infrared Telescope Facility (Mauna Kea, Hawaii), with the U. Texas
mid-infrared echelle spectrometer IRSHELL. This is a 21 spatial by 64
spectral array, with a step size of 0.8 arcsec. Observations were
conducted at a spectral resolution of $\sim$15000. We detected ammonia
emission at wavelengths of 908 and 948 cm$^{-1}$ over the K impact site
at several times after impact: 20 hours, 5 days and 10 days later. HCN
emission was observed 10 days after impact. With each detection, both
the NH$_3$ and HCN emission lines were imaged with a resolution of 1.4
arcsec over a 17 by 6 arcsec swath centered on the K impact site. At
the impact site the ammonia lines were best interpreted with a
distribution mostly above 10 mbar, having a column density of $2-5
\times 10^{17}$ molecules cm$^{-2}$ above 40 mbar. We have derived both
vertical information and horizontal distributions for NH$_3$ and HCN.
The inferred HCN abundance is sensitive to the temperature profile,
which was derived from C$_2$H$_2$ and CH$_4$ line spectra (see poster
by B\'ezard \etal). We observe the ammonia spreading out over a larger
horizontal area with time. Its distribution is depleted with time as a
function of altitude, consistent with photochemical destruction (Moses
\etal 1995). The vertical distribution of the NH$_3$ appears
consistent with dynamical models of the explosion (K. Zahnle, priv.
comm.).
\np
\bc
{\large\bf Microwave Imaging of Jupiter's Troposphere\\
During Impact with Comet P/Shoemaker-Levy~9}\\[6pt]
\bi
A.~W. Grossman and S.~M.~White (Univ. of Maryland),\\
D.~O.~Muhleman and M.~A.~Gurwell (Caltech)\\[6pt]
\ei
\ec
We report on the results from a world-wide campaign to acquire
high-resolution, microwave images of thermal emission from Jupiter's
troposphere, before, during, and after impact with fragments of comet
P/Shoemaker-Levy 9. Interferometric observations were obtained at wavelengths
of 3cm and 6cm from the Very Large Array (VLA) and the Australia Telescope (AT).
At these wavelengths, gaseous ammonia is the primary source of opacity in
Jupiter's troposphere. It is also the principal condensate. Therefore changes in
brightness temperature are indicative of changes in ammonia abundance and
relative humidity. The corresponding weighting functions at these wavelengths
probe the pressure levels 1-10 bars, below the optically thick cloud deck.
Preliminary images at centimeter wavelength clearly show the expected zone-belt
structure. Two prominent features in the radio data are a distinctly bright band
at the position of the North Equatorial Belt (NEB) and a corresponding dark band
at the position of the Equatorial Zone (EZ). The 30K brightness temperature
difference (at a wavelength of 6cm) between these two regions, interpreted
within the context of a radiative transfer model, requires that the NH${}_3$
mixing ratio decrease by a factor of two from the EZ to the NEB.
At the latitude of the impacts there are no discernible features at a level of
3-5K within a 3000-5000 km beam-width. This constrains the change in the average
NH${}_3$ abundance within this region to value of less than 10\%, although
larger changes in NH${}_3$ abundance are allowed in a smaller region. These
limits may constrain the depth of penetration of the comet fragments. Work
continues to reduce the full complement of data taken during the week of impacts
and to improve the sensitivity and quality of the images.
\np
\bc
{\bf EUVE Observations During the Comet Shoemaker Levy/9 Impacts}\\[6pt]
\bi
D. T. Hall\\
Center for Astrophysical Sciences\\
The Johns Hopkins University\\
Baltimore, MD~21218\\[6pt]
G. R. Gladstone\\
Southwest Research Institute\\
6220 Culebra Road\\
San Antonio, TX~78228\\[6pt]
\ei
\ec
The Extreme Ultraviolet Explorer satellite conducted extensive observations
of the Jupiter system before, during and after the arrival of the fragments
of Comet Shoemaker-Levy/9. Approximately 500,000 seconds of data were
acquired in 1994. Previous observations of the Jupiter system revealed that
electron-impact generated line emission from oxygen and sulfur ions resident
in the Io plasma torus dominate the spectrum in the 37 to 73~nm range; these
emissions dimmed 30--50\,\% during the impact events, and no new torus
emissions were detected. Because no similar reduction in Io torus output was
observed at longer wavelengths, the EUV luminosity reduction was very likely
caused by a reduction in the population of high-energy Io torus electrons
($Ee > 17$\,eV), which excite a large fraction of the EUV emissions but a
comparatively small fraction of longer wavelength emissions. Following
several of the impacts, EUVE detected transient brightening events in
planetary atomic helium resonance emission, HeI 58.4~nm, which was barely
detected before the impacts ($I \approx 3$\,Rayleigh), although it was measured
by the Voyager spacecraft during 1979 ($I = 4$\,Rayleigh). After the impact
of fragment Q1 the HeI 58.4~nm brightness increased to 25--70 Rayleigh,
or about 8--25 times the average brightness of Jupiter before the impacts.
The brightening events indicate that the impacts lifted substantial amounts
atomic helium to high altitudes in Jupiter's atmosphere, above much of the
molecular hydrogen gas that normally absorbs HeI 58.4~nm photons emitted
from lower altitudes.
\np
\bc
{\bf An Interpretation of Calar Alto Ground-Based Infrared Lightcurves}\\[6pt]
\bi
D.P. Hamilton (Max Planck Institut f\"ur Kernphysik, Heidelberg), \\
T.M. Herbst (Max Planck Institut f\"ur Astronomie, Heidelberg),\\
H. B\"ohnhardt (Universitats-Sternwarte, M\"unchen),\\
J.L. Ortiz (Instituto de Astrofisica de Andalucia, Granada),\\
A. Richichi (Max Planck Institut f\"ur Astronomie, Heidelberg), and\\
G. Calamai (Osservatorio Astrofisico di Arcetri, Italy).\\[6pt]
\ei
\ec
We describe 2.3\mic~and 3.1\mic~data obtained at Calar Alto's
3.5-meter and 2.2-meter telescopes during the impacts of
Shoemaker-Levy 9 fragments A,E,H,L,Q1,Q2, and S with Jupiter. All of
these impact events produced significant brightening of the jovian
disk lasting on the order of 10-20 minutes. These ``main events'' are
the brightest features seen by infrared and optical telescopes. Five
of the impacts - those for fragments A,H,L,Q1, and Q2 - show fainter
precursor features which begin roughly five minutes before the main
events. For impacts H and L, there are additional features at still
earlier times. These sharp H and L first precursors rise, peak, and
begin to fade before the onset of the signals detected by Galileo's
PPR instrument.
Signals from Jupiter might be expected from several stages of each
impact including the bolide entry into the jovian atmosphere, the
rising impact shock wave and fireball, reflected sunlight and thermal
emission from the ejecta plume, reimpacting ejecta, and the rotation
of the glowing impact site into view. Interpretations are difficult
due to the far-side location of the impact sites and the changing
geometry from one impact to the next. We present our infrared
lightcurves and attempt to interpret specific features in these curves
in terms of physical mechanisms.
\np
\bc
{\bf Observations of the Dynamic Response of Jupiter's Atmosphere to
the Impact of Comet Shoe\-maker-Levy 9}\\[6pt]
\bi
J.\ Harrington,
T.\ E.\ Dowling,
C.\ M.\ Santori,
H.\ B.\ Hammel,
J.\ R.\ Mills (MIT),\\
A.\ P.\ Ingersoll (Caltech),
R.\ F.\ Beebe (NMSU),\\
G.\ S.\ Orton,
P.\ Chodas,
D.\ Yeomans (JPL)\\[6pt]
\ei
\ec
We present HST images of impact sites A, E, G, Q1, and R during their
first planetary rotations (Hammel et al., Science, 1995). They each
show one or two rings expanding from the impact site and located above
the atmospheric methane ($P < 380$ mbar). Outer ring radius
varies linearly with time at a velocity of 454$\pm$20 m/s. The inner
ring fit gives 353$\pm$83 m/s. We interpret the rings as signatures of
stratospheric inertia-gravity waves, with the outer ring speed
indicating a deformation radius of $\sim$1,800 km, consistent with
current estimates. The observed outer ring speed corresponds to the
$\sim$400 m/s waves in the 16--69 mbar layer of our pre-impact model
(Harrington et al., Nature, 1994). Tropospheric IG wave speeds in this
model and that of (Ingersoll et al., GRL, 1994) are closer to 100 m/s.
The latter model predicted that a water-cloud wavefront (5 bars
pressure) would affect the stratosphere. However, the observed outer
wave moves too fast to be driven from the troposphere; this is also
likely true of the inner wave. One possibility for faster
tropospheric waves in that model is a water abundance many times that
of estimates based on solar composition.
This work was supported by NASA.
\np
\bc
{\bf Jeans Instability in Comet Shoemaker--Levy 9}\\[6pt]
\bi
Joseph M. Hahn and Terrence W. Rettig\\
University of Notre Dame\\[6pt]
\ei
\ec
Recent $N$--body simulations of a tidally disrupted
comet ({\it e.g.}, Asphaug and Benz 1994)
indicate that gravitational instabilities may be
responsible for the appearance of comet
Shoemaker--Levy 9. These models show that if
the comet catastrophically fragmented into $N\gg20$ parts, the particles
can gravitationally recondense into $n$ fragments a few hours after periapse.
Since $n$ depends sensitively on the parent comet's density $\rho$,
catastrophic disruption of a comet provides a sensitive measure of its
density. We show, via a
tidal impulse model, that if tides disrupted S--L 9 into a cloud of many particles,
the resulting cloud is Jeans unstable and condenses to $\sim20$ fragments
about 10 hours after periapse for a comet density $\rho\sim0.6$ gm/cm$^3$.
Whether these instabilities condense to compact objects or remain as extended swarms
depends upon the rate at which
particle collisions might damp their random motions.
We also show that a varicose instability in an
incompressible medium cannot account for S--L 9's twenty fragments, for this
instability quickly breaks up a tidally elongated cylinder into only
$n\sim{\cal O}(1\mbox{ or 2})$ fragments.
These results indicate that a particle gas equation of state can be
representative of catastrophically disrupted comets.
\np
\bc
{\bf Cometary Impact Lightcurves and Optical Depth Variations of\\
the Impact Plumes}\\[6pt]
\bi
Hitoshi Hasegawa, Satoru Takeuchi, Takuya Yamashita, Kazu Sekiguchi,\\
and Jun-ichi Watanabe\\[6pt]
\ei
\ec
During the impacts of comet P/Shoemaker-Levy 9, we obtained several
light curves of the impacts at near-infrared wavelenghts at the Okayama
Astrophysical Observatory (OAO) and the South Africa Astrophysical
Observatory (SAAO). Impacts of larger fragments showed multiple
flashes. The largest impact that we observed was the fragment K, and it
showed triple flashes. The first faint flash and subsequent secondally
flash are thought to be an entry flash of bolide phase and its expanding
plume over Jovian horizon respectively. The first entry flash might be
missed in most of the smaller fragments. The all of the third flash
appeared 6-7 minutes after their impact times and are the brightest. We
tried to investigate the lightcurves in terms of optical depth variation
of the impact plume. A nucleation theory in the solar composition
gas was applied to the expanding plume gas. We suggest that the secondary
flash was mainly due to gas phase opacity variation and that grain
formation of cometary originated silicate dusts will contribute a large
amount of the brightest third flash.
\np
\bc
{\bf Reflectivities of the Cometary Impact Sites}\\[6pt]
\bi
Hitoshi Hasegawa, Satoru Takeuchi, Takuya Yamashita, and
Jun-ichi Watanabe\\[6pt]
\ei
\ec
Observation of the cometary impact sites of comet P/Sheomaker-Levy 9
at near-infrared wavelengths were carried out with a near infrared
imaging system OASIS at the Okayama Astrophysical Observatory.
The observed wavelengths are the strong methane absorption band at 2.3
micron, intermediate methane absorption at 1.7 micron, and 2.2 micron.
Theese impact sites showed as brighter clouds on the disk. The
reflectivities of several impact sites were measured from these
images at these different wavelengths. Center to Limb variation curves
indicate that their cloud top located at the stratosphere about 1 - 2
mbar. The material of the aerosol particle is still unknown, but we
suggest that magesium silicate dust nucleated in the explosion plume for
the most plausible candidates of the grain.
\np
\bc
{\bf Near Infrared Spectroscopy and Long-Term Monitoring of the
SL-9 Impacts}\\[6pt]
\bi
T. M.Herbst (Max-Planck-Institut f\"ur Astronomie, Heidelberg)\\
D. P.Hamilton (Max-Planck-Institut f\"ur Kernphysik, Heidelberg)\\
H. B\"ohnhardt (Universit\"ats--Sternewarte, M\"unchen)\\
J. L. Ortiz-Moreno Instituto de Astrofisica de Andalucia, Granada\\[6pt]
\ei
\ec
We present K band spectra taken during the H and L impacts and attempt
to derive physical conditions in the emitting regions. Prominent
spectral features due to CO and methane indicate temperatures in
excess of 2000 K near maximum light. These spectral lines faded within
minutes. Monitoring of the impact sites in the days, weeks, and
months after the collision shows longitudinal spreading of the ejecta
structures at a rate of ~10 m/s. The resulting band displayed
significant inhomogeneities as late as February 1995. Although still
prominent at 2.3 microns, the band has faded considerably since solar
conjunction.
\np
\bc
{\bf The Collision of Comet P/Shoemaker-Levy 9 and Jupiter}\\[6pt]
\bi
John J. Hillman, David A. Glenar, William C. Maguire, Gordon Chin,\\
William E. Blass$^{1}$ and Miska Le Louarn$^{2}$\\[6pt]
Laboratory for Extraterrestrial Physics\\
NASA/Goddard Space Flight Center\\
Greenbelt, MD\\[6pt]
\ei
\ec
\bi
$^{1}$Department of Physics and Astronomy\\
Univ. Tennessee, Knoxville, TN\\
$^{2}$Universities Space Research Association, Seabrook, MD\\[6pt]
\ei
We observed the southern hemisphere of Jupiter on two nights during this
impact sequence, using the Coude focus at the Kirtland Air Force Base, 1.5-
meter adaptive optics telescope. Our objectives were to recover a set of
scattering properties and likely vertical distributions of material at the
impact site locations. Multispectral images were acquired in the methane
bands at 725- and 890-nm and in their adjacent continuum using an acousto-
optic tunable filter (AOTF) imaging spectrometer with a silicon CCD at the
focal plane. The stratosphere near 1-mbar was simultaneously sounded by
imaging in the deep 2.35-micron methane band using a NICMOS-3 camera with
cooled narrow band (0.05-micron FWHM) filter.
All observations were photometrically calibrated and reduced to absolute
reflectivity (I/F) using close coincidence standard stars and published solar
intensities. We subsequently narrowed the observed point spread function in
the images by employing a modified inverse Fourier deconvolution algorithm and
then renormalized to the original I/F scale.
For the "quiet" atmosphere we have adopted a vertically inhomogeneous atmos-
pheric model using two clouds and a high-level thin haze which was optimized
to fit our observed Jupiter center-to-limb I/F variations. We then inter-
leave a collision site layer with a variable top and bottom boundary, optical
density, single-scattering albedo and phase function. Results on several
collision sites will be presented.
\np
\begin{center}
{\bf The Search for Historical Impact Sites on Jupiter}\\[6pt]
{\it Thomas Hockey, University of Northern Iowa}\\[6pt]
\end{center}
A search was made through historical reports of major dark spots on Jupiter,
recorded during the pre-photographic era. While many of these reports meet the
sufficient condition for impact candidacy (exogenic origin cannot be ruled
out), the descriptions and drawings lack the detail required to meet the
necessary condition (a morphology similar to that created by the Shoemaker-Levy
9 impacts). The lack of available information about specific historical spots
on Jupiter is a consequence of the perceived physical nature of these spots at
the time, and the traditional purpose of jovian spot observations.
\newpage
\bc
{\bf Direct Observations of the Comet Shoemaker-Levy 9
Fragment G Impact by Galileo UVS}\\[6pt]
\bi
C. W. Hord (1), W. R. Pryor (1), W. K. Tobiska (2), A. I. F. Stewart (1),
K. E. Simmons (1),\\
J. J. Gebben (1), C. A. Barth (1), W. E. McClintock (1),
L. W. Esposito (1),\\
R. A. West (2), S. J. Edberg (2), J. M. Ajello (2),\\
and K. L. Naviaux (2)\\[6pt]
\ei
\ec
\bi
(1) Laboratory for Atmospheric and Space Physics\\
University of Colorado\\
Boulder, CO 80303\\[6pt]
(2) Jet Propulsion Laboratory\\
California Institute of Technology\\[6pt]
\ei
The Galileo Ultraviolet Spectrometer (UVS) team has detected the
Shoemaker-Levy 9 fragment G impact on Jupiter in data recently played back
from the spacecraft tape recorder. A 20\% brightening of the disc-integrated
signal of Jupiter was detected at 292 nm during a swath across Jupiter that
lasted $1.6$ sec and was centered at 1994-July 18 (day 199)/07:33:31 UT (all
times in this paper are corrected to be the time of the event as seen from
Earth). The emission brightness, when combined with simultaneous
Photopolarimeter Radiometer (PPR) measurements at 945 nm, is consistent with
thermal radiation at a temperature of 7800 ($+$500, $-$600) K emitted over an
area of 40 ($+$60, $-$25) km$^2$. No excess signal was seen during
swaths $5.33$ sec before and after the detection swath.
\np
\bc
{\bf On Particle Acceleration by the Impact-driven Field-aligned
Current System}\\[6pt]
\bi
W. H. Ip\\
Max-Planck-Institut fuer Aeronomie\\
D-37191 Katlenburg-Lindau, FRG\\[6pt]
\ei
\ec
Following the scenario that a localized atmospheric wind system will be
generated at the comet impact sites as a result of the energy release
from atmospheric explosion (Hill and Dessler, 1995; Ip, 1995), a simple
model is constructed to estimate the possible ranges of the electric current
flows and the associated potential drop. The particle acceleration effect
caused by a potential drop of 100 eV - keV along the magnetic field line
could in turn produce the ultraviolet emissions observed by HST after the
K impact. Such ionospheric dynamo mechanism might have some interesting
implication on the energy budget of the Jovian thermosphere as well.
\np
\bc
{\bf On the Ballistic Nature of the Shoemaker-Levy~9 Impact Plumes
A,E, and G}\\[6pt]
\bi
Kandis Lea Jessup (University of Michigan, AOSS)\\
John T. Clarke (University of Michigan, SPRL)\\
Heidi B. Hammel (M.I.T.)\\[6pt]
\ei
\ec
We present the time evolution of the plumes associated with SL9
impacts A, E, and G. Our results are based on the analysis of
real time HST WF/PC2 images for each event, as well as those of
the ejecta pattern imaged 1-2 hours subsequent to each event.
From these images we have determined altitude above the limb and
displacement in the plane parallel to the "surface" of the
planet for each plume as a function of time. We have also cal-
culated the ballistic trajectories necessary to reproduce each
ejecta pattern, including coriolis deflection, for comparison.
Thus we have reconstructed the flight of each plume, constraining
the location at which the material descends through the atmosphere
of Jupiter and the initial timing of each explosion event.
\np
\bc
{\bf Comet Capture Statistics}\\[6pt]
\bi
D. M. Kary\\
UCSB\\[6pt]
L. Dones\\
San Jose St.\\[6pt]
\ei
\ec
Before being observed, Comet P/Shoemaker-Levy 9 had orbited
Jupiter for several decades (L. Benner, W.B. McKinnon 1994, BAAS 26, 1564).
We have investigated
comet capture statistics through numerical simulations of
test particles with orbits like those of Jupiter-family comets.
We did 4-body point-mass integrations (Jupiter, Saturn, Sun, and comet),
following the orbits of $\sim3\times 10^4$ bodies for $\sim10^5$
years. Over $2.7\times 10^5$ captures occured.
Of the $2.1\times 10^4$ captures which make 1 or more orbits
around Jupiter, $<0.2\%$ make 20+ orbits
(corresponding to 50+ years) around Jupiter.
Of the captures which get closer than $2.4R_J$, 4.4\%
made 20+ orbits. Provided close passage is necessary
for making a captured comet observable,
the bias in favor of long-term capture events is significant.
This work is supported by NASA Planetary Geology and
Geophysics Grant \# NAGW-2061 at UCSB and by RTOP 151-01-60-09 at NASA
Ames.
\np
\begin{center}
{\bf Infrared Spectroscopy of Jupiter's Atmosphere after the A, D,
and E Impacts of \mbox{Comet P/Shoemaker-Levy 9}}\\[6pt]
\begin{it}
Sang J. Kim\\
Department of Astronomy and Space Science\\
Kyunghee University\\
Yongin, Kyunggido, Korea\\
and\\
Department of Astronomy\\
University of Maryland\\
College Park, MD 20742, USA\\[6pt]
Glenn S. Orton\\
Jet Propulsion Laboratory\\
MS 169-237\\
2800 Oak Grove Dr.\\
Pasadena, CA 91109, USA\\[6pt]
Christophe Dumas\\
Institute for Astronomy\\
University of Hawaii\\
2680 Woodlawn Dr.\\
Honolulu, HI 96822, USA\\[6pt]
\end{it}
\end{center}
Infrared spectra of Jupiter's atmosphere were obtained with
the Infrared Spectrometer (IRS) on the 1.5-m telescope at
the Cerro Tololo Inter-American Observatory (CTIO) during the
first two days of the impacts of the fragments of Comet \mbox{Shoemaker-Levy 9}
(1993e). We monitored 2 - 4 micron radiation from the impact areas,
undisturbed areas, and auroral regions of Jupiter after
the A, D, and E impacts. The strong emission of the
3 micron band of methane was detected on the A impact area 4 hours after
the impact. Emissions of trihydrogen ions decreased at the A and E impact sites compared with undisturbed areas at the same latitude. The
temperatures of trihydrogen ions in the southern auroral region were normal
within the first several hours following the A, D, and E impacts.
\newpage
\begin{center}
{\bf Sizes of the Comet SL9 Secondary Nuclei A and Q2 Calculated on the
Basis of Physical Parameters of Light Echoes from Europa and Io}\\[6pt]
\begin{it}
Kleshchonok V.V., Churyumov K.I.\\
Astronomical Observatory of Kiev University, Ukraine\\[6pt]
\end{it}
\end{center}
On the basis of high-speed photoelectric observations of Europa and Io,
fireball flashes in the atmosphere of Jupiter during the impacts
of fragments A and Q2 of comet SL-9 were recorded. The
flash of the A fragment on July 16, with an amplitude of 0.12 mag and
a duration of 0.7 sec, was recorded during observations of
Europa. The flash of the Q2 fragment on July 20, with an amplitude
of 0.11 mag and a duration of 1.0 sec, was recorded during
observations of Io. Analogous parameters of the second flash were
obtained at the Vatican Observatory [1]. The data allowed us to
estimate the energy of the flashes and fragment radii. Taking into
account the paper by Sekanina [2] that in light energy of
fireball radiation transforms 1% from kinetic energy of secondary
nucleus of comet SL-9 during its impact with the Jupiter
atmosphere we will obtain the following estimate for sizes of
secondary nuclei A and Q2 of SL-9: R(A)=1.42 km for $\rho$=0.3 g/cm3
(1.00 km for $\rho$=1.0 g/cm3); R(Q2)=0.65 km for $\rho$=0.3 g/cm3 (0.43 km
for $\rho$=1.0 g/cm3 ).
In the paper by Hammel H.B. and Nelson R.M. [3] parameters of
flashes of brightness of Io that had the amplitude about 0.5 mag
and that was observed July 26, 1983 are given. This observation
was obtained with the 1.52-m telescope through 420 nm filter at
the Palomar observatory.Though the flash on Io that was registered
by Hammel and Nelson is noticeably greater then the one we
registered in 1994 on Jupiter after July 26, 1983 there was not
observed a somewhat visible new spot that can be compared with
those spots that were formed on Jupiter after the collision of
comet SL-9 with Jupiter. This fact is evidence of that that the
flash of brightness of Io in 1983 was not caused by light echo
from a possible fireball on Jupiter. The most probable reason for
this flash to occur could be fall down on Io of 1-2 km asteroid
or icy cometary nucleus. As a result of this collision from
Io's surface a chain of bodies containing matter from the surface
layers of Io whose composition as is known comprise Na, S2 and
other elements could be exploded. Bodies exploded from the surface
of Io, we think, could form a cometary train that in 1993 was
detected by Shoemaker and Levy as a new comet consisting of 21
secondary nuclei.\\
References:\\
1. G.J.Consolmagno and G.Menard. A Search for Light Echoes of A,
H, and Q Events. European SL-9/Jupiter Workshop. February 13-15,
1995. Garcbing, Germany, p. 25-26.\\
2. Sekanina Z. Disintegration phenomena expected during collision
of comet SL-9 with Jupiter. Science, 262, p.382-387 (1993).\\
3. Hammel H.B. and Nelson R.M. Bright flash on Jupiter in 1983.
Nature, 1, N11, p.46 (1993).
\newpage
\begin{center}
{\bf Near-Infrared Spectroscopy of the R Impact Site of Comet
\mbox{Shoemaker-Levy 9}}
\vspace{1cm}
R.F. Knacke$^{1}$, S.B. Fajardo-Acosta$^{1}$, T.R. Geballe$^{2}$,
\& K.S. Noll$^{3}$\\
\end{center}
\vspace{1cm}
\noindent $^{1}$ Penn State Erie, The Behrend College, Erie, PA 16563
\noindent $^{2}$ Joint Astronomy Center, University Park, Hilo, HI 96720
\noindent $^{3}$ Space Telescope Science Institute, Baltimore, MD 21218
We present 2.20--2.41 $\mu$m spectroscopy of the R event of Comet
Shoemaker-Levy 9, spanning approximately 45 minutes prior, during, and after
the impact. We model the spectra with temporally variable column
abundances of mainly CH$_{4}$ and CO. The CO 2--0 bandhead is visible
during and shortly after the impact event, implying temperatures $\geq$
2000 K. The 3--1 and 4--2 CO bandheads are possibly present in some spectra,
blended with CH$_{4}$ lines. Therefore some of the CO could have reached
temperatures $\geq$ 3000 K. Absorption on the red side of the 2--0 bandhead
by cooler ($T \approx 1000$ K) CO is also evident.
\newpage
\begin{center}
{\large \bf CCD Spectroscopy of Jupiter's Crash Latitude\\ in 4600-10,240 \AA{}
Wavelength Region\\}
\medskip
P.P.\,Korsun$^{1}$, Yu.V.\,Sizonenko$^{1}$,\\
S.G.\,Sergeev$^{2}$, and S.V.\,Berdyugina$^{2}$
\end{center}
1 Main Astronomical Observatory, Kyiv, Ukraine
2 Astrophysical Observatory, Nauchny, Crimea, Ukraine
\bigskip
\noindent The impact sites of the fragments of the Comet Shoemaker-Levy 9
in the Jovian atmosphere were observed using the 2.6-m Shajn Telescope
of the Crimean Astrophysical Observatory. We obtained long-slit
CCD spectra of the spots DGRS, FTVE, H, K, KUW, L, and N at the
Nasmyth and coude foci. The Nasmyth spectra covered the spectral
region from 4600 to 10,240 \AA{} at a resolution of 4.5 \AA. The coude
spectra were obtained at the methane band (8900 \AA) and at 5893 \AA{}
(Na doublet) with resolution 0.85-1.7 \AA.
We investigated both the spatial structure of the impact sites
along the crash latitude, and spectral peculiarities along
dispersion. All the spots were seen in absorption in the observed
spectral region except for the CH$_{4}$ bands at 8900 \AA{} and
10,000 \AA, where they were brighter then undisturbed Jovian surface.
Some spots showed spectral peculiarities at 7200 \AA{} (CH$_{4}$)
and 7900 \AA{} (NH$_{3}$) as well. We had not detected any Na variation
in our coude spectra.
\newpage
\bc
{\bf POSSIBLE 29MHz PRECURSORS ASSOCIATED WITH SOME
COMET SL9/JUPITER IMPACTS FROM RATAN-600 OBSERVATIONS}\\[6pt]
\bi
Korzhavin A.N., Bogod V.M., Dikij V.N., Dikij D.V., Komar, N.P.\\
Special Astrophysical Observatory of the Russian Acad. Sci.,\\
Pulkovo Branch, SAO, Pulkovo, St.Petersburg, 196140, Russia\\[6pt]
\ei
\ec
Decametric radio observations of Jupiter were made during July 16
to 22, 1994 from the North Caucasus with the RATAN-600 radio telescope
of Special Astrophysical Observatory of the Russian Academy of Sciences.
A special feeder sistem was designed with a purpose to form a beam
(with the main mirror) of about 15 degree width in the E-W direction
allowing to make an observational session of up to one hour duration.
Both right-hand and left-hand polarizations were recorded at frequency
30 MHz with 1 MHz bandwidth and 10 milliseconds time resolution. A total of
20 observational sessions of 30 - 60 minutes duration have been made.
Four of them encompass impact times of some comet SL9 fragments with Jupiter
and are discussed in this paper.
Summarizing our data, we conclude that there is a quite high
probability that each comet SL9 fragment produced a
precursor burst event at decametric wavelengths when
passing throughout low levels of the Jovian magnetosphere.
There are also some post impact burst events.
If so, the unique event, the collision of comet P/Shoemaker-Levy 9
and Jupiter, gives us an unprecedented opportunity to study the
structure of the low levels of the Jovian magnetosphere (the last
20,000 Km of each fragment orbit) with a spatial resolution
as high as 1-2 Km, which corresponds to our 20-40 millisecond
time resolution.
\np
\begin{center}
{\bf On the spatial distribution of fragments of Comet
Shoemaker-Levy near Jupiter}\\[6pt]
{\it N.Ya. Kotsarenko, K.I.Churyumov, V.N. Mal'nev, and A.N.
Kotsarenko\\Kiev University, Ukraine}\\[6pt]
\end{center}
The fragment parameters of comet Shoemaker-Levy and their spatial
distribution before entering the atmosphere of Jupiter have been
determined with sufficient accuracy. Special attention must be given
to the geometry of the string-of-pearls chain of fragments that were
arranged along straight line on approximately equal distances
between large fragments.
\par Evidently such spatial distribution of fragments could be a
result of explosion of the comet or could be formed by fragment
interaction. Moving in strong nonhomogeneous gravitational field of
Jupiter fragments weakly attract and repulse each other because of
elasticity of gas atmospheres that surround each fragment. From the
balance of the average attraction force of proper gravitation and
the repulsion force of the atmospheres in the stationary regime we
obtained the correlation between an average distance $l_i$ between
fragments, their masses $m_i$ and average density number $n_0$ of
the gas atmosphere particles and their effective temperatures.
\par It happened to be that $l_i\sim\sqrt{m_im_{i\pm1}}$ ( $m_i$ are
masses of neighbour fragments). This formula may explain the
observable fact that distances between light fragments are smaller
than distances between bigger fragments. The time of the interaction
transmission in this system is estimated. More detailed comparison
of the theory with the observed results may be made if more exact
density number of the gas atmosphere $n_0$ is known.
\newpage
\bc
{\bf VLA Observations of the Effects of the Shoemaker-Levy~9
Impact on the Synchrotron Emission from the
Jovian Magnetosphere}\\[6pt]
\bi
A. Kundu, A. W. Grossman, J. C. L. Wang \& S.M. White (Univ. of Maryland)\\
D. O. Muhleman and M. A. Gurwell (Caltech)\\[6pt]
\ei
\ec
We observed the Jovian system with the VLA in the X-Band (3 cms) and
the C-Band (6 cms) during the week of the impact. High resolution
interferometric images of the linearly polarized emission from
Jupiter's magnetosphere were obtained. The source of the polarized
emission at these wavelengths is synchrotron emission by high energy
electrons trapped in the inner magnetosphere. The intensity and
morphology of the synchrotron radiation is dependent on the
configuration of the Jovian magnetic field with respect to earth, the
energy of the electrons, and their pitch angle
relative to the magnetic field.
Our maps resolve the detailed structure of the emission out to 2.5
jovian radii with a spatial resolution of 1.5 arcsecs. Snapshot images
at different central meridian longitudes show a prominent region of
extended emission along the magnetic equator on either side of the disk
of Jupiter. Regions of diffuse emission are also observed at high
magnetic latitudes, due to the relativistic electrons with small pitch
angle at the equator. The flux from each of these regions was observed
to increase by a factor of 1.2-2 in the post-impact maps. The position
of the peaks of the emission migrated closer to the disk of Jupiter by
up to 6 arcsecs. Comparison of the fluxes at the two wavelengths
reveal a decrease in the spectral index of electrons with an energy of
25-35 MeV.
The synchrotron emission is observed over a more extended region, both
radially and (magnetic) latitudinally in the post-collision images of
Jupiter's magnetosphere. This suggests an infusion of high energy
electrons at large Jovian radii and possibly an inward radial diffusion
of the radiating electrons. The latidudinal expansion of the emission
regions may by explained by the infusion of electrons with intermediate
pitch angles.
The morphology of the synchrotron emission shows strong time dependent
changes corresponding to the changing geometry of the magnetic field as
seen from the earth. The interpretation of the change in the various
components of the synchrotron radiation at different longitudes is the
subject of an ongoing study.
\np
\bc
{\bf 10 microns Observations of SL-9 Impacts with CAMIRAS at NOT}\\[6pt]
\bi
P.O. Lagage, Ph. Galdemard, R. Jouan, P. Masse, E. Pantin, M. Sauvage (CEA,
DSM/DAPNIA/Service d'Astrophysique, CE Saclay, F-91191 Gif-sur-Yvette; e-
mail Lagage@sapvxa.saclay.cea.fr); B. Mosser (IAP); G. Olofsson, M.
Huldtgren (Stockholm Observatory); J.A. Belmonte, C. Regulo, T. Roca
Cortes, J.M. Rodriguez Espinosa, M. Selby, L. Vidal (IAC); D. Gautier
(Observatoire de Meudon); A. Ulla (NORDICA)\\[6pt]
\ei
\ec
From July 16th to July 27th, Jupiter was imaged with CAMIRAS, the Saclay
mid-IR camera, mounted on the 2.5 m Nordic Optical Telescope (LaPalma
island, Spain). The 10-13 micron filter and the 0.9 arcsec PFoV (total
field: 57x57 arcsec**2) were used. The weather conditions were fine. Out of
the 10 impacts observed (A, E, F, H, L, P2, Q1, Q2, T, U), 5 were detected
(A, E, H, L, Q1).
The light curves obtained within 1 hour after the detected impacts are
quite similar. They will be discussed in terms of plume rising above the
limb (precursor flash about 2 min after Galileo detection), fall-back of
material into the atmosphere (main IR peak about 13 min after impact), and
sun-heated dust (bump about 20 min after impact and subsequent emission).
The prime aim of the observations was the search for thermal fluctuations
associated with seismic waves excited by the comet fragments. Direct
information about the internal structure of Jupiter can be derived from the
arrival times at various distances from the impact. The results of the
search will be presented.
\np
\bc
{\bf REDUCED FIVE MICRON LIGHT CURVE OF THE COMET SL-9 JUPITER
R-IMPACT FEATURE FROM THE AIR FORCE MAUI OPTICAL STATION}\\[6pt]
\bi
J. V. Lambert, V. L. Porter\\
Rockwell Space Operations Company\\[6pt]
J. L. Africano, D. L. Nishimoto, R. A. Nolan\\
Rockwell Power Systems\\[6pt]
P. Kervin, R. Medrano\\
Phillips Laboratory\\[6pt]
\ei
\ec
A 4.8 to 5.08 micron infrared light curve of the Comet Shoemaker-Levy 9
fragment R impact on Jupiter was derived from infrared imagery obtained
using the Enhanced Longwave Spectrometer/Imager (ELSI) on the Phillips
Laboratory 1.6-meter telescope at the Air Force Maui Optical Station (AMOS).
The impact site became visible as it reached the planet's limb, eight
minutes after the estimated impact time, then faded rapidly, within ten
minutes. There is an indication of a precursor event at four and one half
minutes after impact. The two-second temproal resolution light curve
contains multiple maxima. The imagery was processed to obtain estimates of
the impact feature peak intensity and diameter. Some five micron imagery of
the C and F impacts was also obtained, as well as a few frames of the R
impact in the 8 to 13 micron band.
\np
\begin{center}
{\bf Jovian Decametric Radio
L-bursts Associated with the Impact of
Comet SL9\\
and Jupiter}\\[6pt]
\begin{it}
Xiao-Cong Li and Xi-Zhen Zhang\\
Beijing Astronomical Observatory\\
Chinese Academy of Sciences\\
Beijing 100080\\[6pt]
\end{it}
\end{center}
The characters of two decametric radio L-bursts possibly associated with the
impact of Comet SL-9 and the Jupiter are briefly described. Two L-bursts
occurred on July 21,1994. They took place 55 minutes before and 13 minutes
after the impact of the fragment S with the Jupiter respectively. These two
radio L-bursts have been recorded at frequencies from 24.0MHz to 28.5 MHz by
Beijing \thinspace Astronomical Observatory and China Research Institute of
Radio Wave Propagation
The bursts have distinct peak flux densities and durations.
except the effect of emission from Io satellite, The peak flux
densities are generally 7-8 times than that of a normal one, the longest
duration is 266s. The burst occurred after the impact is coresponding
with the brightening at infrared wavelength. Their spectral characters are
different from that of a normal L-burst.
The time profiles of the two bursts have opposite frequency drifts, and
the profiles after low pass filtering(0.01Hz) have opposite arc
curvatures(one is early and another later). The drift rate of the burst
occurred before the impact is -377KH$_z$ , that of another one is +463.9KHz.
However the profiles of two
bursts are similar at ten frequencies. Their flux densities reached the
maximum at 25 MHz. Along with the directions of frequency drift, their line
profiles of curves became more simple, and their durations became shorter.
The spectral characters of these two bursts mentioned above seem to show
that the two bursts excited in a similar way by the impact of the fragment S
with the Jupiter.
This paper was supported by The National Nature Science Foundation of China
and the Chinese Academy of Sciences.
\newpage
\title{
Three strong Jovian decametric radio bursts from impacts
%
}
%
\author{
Qi-Bin Li,
Xi-Zhen Zhang,
Jin-Lin Han
\\
%
{\small{\it Beijing Astronomical Observatory, Chinese Academy of
Sciences, Beijing 100080, P.R. China}}
}
\maketitle
\begin{abstract}
Three strong decametric radio bursts ($>$20db), undoubtedly
related to the impacts of fragments G, K, and W of Comet
Shoemaker-Levy 1993e (SL-9) on the Jupiter, have been detected
during the impact week at Xin-Xiang temporary Jovian Decametric
Watch Station of Beijing Astronomical Observatory. All of them
are narrow band events occurred at about 26.0 and 28.5MHz, and
have a long duration of at least several minutes. Their
completely different characteristics, (ie. strongest one before G
impact, immediate response to K impact, and switching bursts
after W impact), are shown in this report.
\\[1mm]
{\bf Key words:} Jupiter, P/comet/SL9
\end{abstract}
\np
\bc
{\bf Temporal Evolution of the SL-9 Impact Features on Jupiter
from CCD Imaging:\\
A Video Animation}\\[6pt]
\bi
Sanjay S. Limaye \& M. Lindgren\\[6pt]
\ei
\ec
Jupiter was imaged from the solar telescope of the Swedish Royal
Academy of Sciences at La Palma (Canary Islands) during the SL-9 impact
week using a broadband filter several times a minute and exposures of
\mbox{0.5 --2 s}.
Typically more than four hundred images were acquired each night for
about four and a half hour period on ten nights. With an image diameter of
almost 600 pixels (0.06 arcsec per pixel), the scale of the spatial features
resolved on the disk of Jupiter is about 700-1400 km, limited mostly by
atmospheric seeing. These images are among the best CCD images of Jupiter
obtained during the impact period from the earth. By mapping these images
into sections of global latitude-longitude maps, the temporal evolution of
the impact features is revealed dramatically, particularly when viewed as an
animated sequence. Typically, all the spots observed on their initial
appearance on the disk predominantly display an apparent drift in longitude
as they move from the morning terminator to the bright limb. The magnitude
and near constancy of the drift rate on successive rotations and the central
meridian transit time measurements suggest that the actual drift rate is
small and that parallax due to immense vertical displacement of the features
is a dominant cause of the observed apparent longitude drift. By also
removing the photometric function, some additional insights into the
evolution of the impact features be obtained. For example, the magnitude of
the minimum brightness of the core region appears to decrease with time for
as many as 12 to 15 hours after the impact and then slowly rise. This might
be indicative of the increasing optical thickness of the core region as
viewed from the earth and then a gradual dispersal in the vertical and
horizontal directions. The video animation sequence of mapped images
illustrates the expanding ejecta around most spots and the distortion in the
apparent shape of the plume as the impact features move across the disk,
most likely due to uncompensated parallax.
\np
\bc
{\bf Modeling of UBVRIJK${\bf'}$ Observations of P/Shoemaker-Levy 9:
Implications for the Dust Size Distribution, Emission History, and Icy Composition}\\[6pt]
\bi
C.M. Lisse (HSTX/NASA-GSFC), M.F. A'Hearn (UMd), P.A. Esterle (UMd),\\
L.A. McFadden (UMd/UCSD), H.A. Weaver (STScI), L.M. Woodney (UMd)\\[6pt]
\ei
\ec
Periodic comet P/Shoemaker-Levy 9 was observed in the UBVRIJK' passbands from
January 1994 through its July 1994 impact with Jupiter from the Kitt Peak
National Observatory (KPNO), the Cierro Tololo Interamerican Observatory (CTIO),
the NASA/Infrared Telescope Facility (IRTF), and the Hubble Space Telescope
(HST). Extended comae and dust tails many arc-seconds in extent were detected
for some 10 of the cometary nuclei.
We have taken the UBVRIJK' images and attempted to fit them using modified
Finson-Probstein/Monte Carlo dynamical models. These models calculate the
classical orbit of a dust particle experiencing the gravitational influence of
the Sun and Jupiter and the radiation pressure of the Sun. The observed dust
tail is then fit by adjusting the rate of dust emission vs time, the velocity of
dust emission vs particle size (b), and the particle size (b) distribution. The
models are typically poorly constrained unless observations over a large angular
scale and a large time range (> 1 month) are made. We present conclusions
concerning the emission history and dust particle size distribution of
P/Shoemaker-Levy from the dynamical models.
We have also combined the images in different passbands to create spectra of the
observed dust. We have then attempted to fit the spectra using a Mie scattering
code modified to allow for porous spheres, multi-component dust, and various
particle size distributions. Cross-checks to the particle size distributions
found by the dynamical modeling were made. We present conclusions concerning the
silicate:carbon:ice composition of the observed dust in the different cometary
nuclei.
\np
\bc
{\bf Five-Color Thermal-Infrared Spectrophotometry of
Selected SL9 Impact Sites}\\[6pt]
\bi
T.A.\ Livengood$^{1,2}$, H.U.\ K\"aufl$^3$, T.\ Kostiuk$^2$,\\
G.L.\ Bjoraker$^2$, P.N.\ Romani$^2$, B.\ Mosser$^4$, M.\ Sauvage$^5$\\[6pt]
\ei
\ec
\bi
1 University of Maryland, College Park, MD\\
2 NASA/Goddard Space Flight Center, Laboratory for Extraterrestrial\\
Physics, Greenbelt, MD\\
3 European Southern Observatory, Garching bei M\"unchen, Germany\\
4 Institut d'Astrophysique de Paris, Paris, France\\
5 SAP CEA, Saclay, France\\[6pt]
\ei
Thermal-infrared imaging of Jupiter was conducted at the European
Southern Observatory in the first 3 days of the SL9 impact week, and for a
week after the impacts. Five of the six filters used have proven to result
in useful spectrophotometric information on the impact sites, spanning the
range 7.7--13.3~$\mu$m. The spectral distribution of impact-site emission
is inconsistent with blackbody thermal emission. The spectra of different
impact sites are also distinct, despite the presumably homogeneous
atmospheric and impactor composition. Presumably, the only variables
between impacts were the fragment size and mass distribution (fragment
swarms versus single fragments). We will report on several impact sites and
investigate the nature of differences between them.
\np
\begin{center}
{\bf Some Results from the Ukrainian Observations of the SL9 Collision with
Jupiter}\\[6pt]
\begin{it}
D.F. Lupishko\\
Astronomical Observatory of Kharkiv University\\
Ukraine\\[6pt]
\end{it}
\end{center}
Within the scope of the Ukraine Program the comprehensive observations
of Jupiter and its sattelites were carried out. Hundreds of
distributions of brightness and polarization along the Jovian central
meridian were obtained before, during and after the collision. Two
splashes of Io brightness were recorded as a result of collision of
comet fragments with Jupiter. These data were used to estimate an
explosion energy, mass and size of fragments. The fast spectral
changes (from 10 sec to 10 min) of intensity of Na, Li, Ca lines and of
$CH_{4}$, $NH_{3}$ and $H_{2}$ were detected. The decrease of methane
absorption at 0.89 and 1 $\mu$m occured to be the overal peculiarity of
the impact sites on Jupiter. It is varied from 10-15$\%$ (medium-sized
spots) to 20-50$\%$ (giant spots). The Doppler shift of some lines is
evidence of very rapid movements of atmospheric matter.
\newpage
\bc
{\bf Thermochemical and Kinetic Modeling of the SL9 Impact Debris}\\[6pt]
\bi
James R. Lyons\\
Caltech\\[6pt]
\ei
\ec
Aerosols and dust particles in a variety of environments typically
have imaginary refractive index k ~ 1E-3 to 1E-2. The particles are
(or are thought to be) heterogeneous, consisting primarily of a weak absorber
(eg. silicates,sulfates) and a small amount of a strong absorber, usually
carbon soot. West et al. (1995) reported k ~ 6E-3 to 3E-2 for the SL9 impact
debris observed at wavelengths from 950 to 250 nm. The relatively flat k
through the visible is strongly suggestive of the presence of a soot-like
compound, either as small (~ 10 nm) soot/graphite particles distributed
throughtout the debris particle, or as some other species with high carbon
content. The stronger absorption exhibited by the debris particles in the
blue and near-uv is qualitatively well-matched by poly-HCN (West et al,1995).
Thermochemical analysis of a mixture of Jovian gas at temperatures ~
1500 to 2000 K and pressures ~ 1E-2 to 1E+2 suggests that a significant
fraction of carbon is present as graphite; at higher temperatures little or
no graphite is seen. However, very low quantites of PAH's and higher
polyacetylenes are predicted, suggesting that in a gas of jovian composition,
the kinetics may be too slow to form appreciable soot. Increasing the C/H
ratio from 1E-3 (Jovian mix) to C/H ~ 1E-1 results in large quantities of
PAH's and polyacetylenes at equilibrium, thus providing rapid pathways for
soot formation. Such a large C/H ratio could only result from cometary
material, and would only yield soot if C > O locally, as might be true
for cometary crust. While abundant HCN is expected, it seems unlikely that
true poly-HCN would form. However, given the lack of chemical data on HCN
polymers, poly-HCN and other less complex HCN polymers cannot be ruled out.
\np
\bc
{\bf Case Study of Enhancement of HST Images of Pre-crash SL9 and Enhancement
Related Considerations}\\[6pt]
\bi
Stephen L. Mahan\\
Gordon Chin$^{*}$\\
William E. Blass\\
Larry Senesac\\
James Rasnake\\[6pt]
Department of Physics and Astronomy \\
The University of Tennessee \\
Knoxville, TN 37996-1200 \\
\ei
\ec
\bi
$^{*}$ Laboratory for Extraterrestrial Physics \\
Goddard Space Flight Center, Greenbelt, MD 20771\\[6pt]
\ei
Using the image restoration methods presented at the STScI Restoration of
HST Images and Spectra II 1993 Workshop (Chin, Mahan, and Blass, Proceedings
p. 49), we have enhanced HST WFPC-I and WFPC-II SL9 pre-crash images.
Correlation of the enhanced images with the observed impacts is presented.
Attempts to recover morphological information from the restored images will
be discussed.
We shall also report on work in progress including an attempt to determine
the point spread function of John Hillman and David Glenar's AOTF imaging
spectrometer coupled to the Kirtland Air Force Base, 1.5 meter adaptive
optics telescope (cf. abstract, this conference) using enhanced HST WFPC-II
images as ''ground truth''.
\np
\bc {\bf 3- and 5-micron spectroscopy of Jupiter at the Canada-France-Hawaii
telescope during the collision of comet SL-9 } \ec
\vs
J.P. Maillard (IAP, France), P. Drossart, B. B\'ezard, C. de Bergh,
E. Lellouch, A. Marten (Obs. Paris, France),
J. Caldwell (York Univ., Canada), J.C. Hilico (Univ. Bourgogne, France),
S.K. Atreya (Univ. Michigan, USA)
\vs
High-resolution spectra of Jupiter were obtained with the Fourier
Transform Spectrometer at the Canada-France-Hawaii telescope
from July 17 to July 21, 1994. They cover different spectral regions
between 1.4 and 5 microns. Important modifications were observed in
3- and 5-micron spectra recorded a short time after the impacts. The 3-micron
spectra observed just after impacts C and R, using a 2.5 arc-sec
aperture centered on the collision sites, reveal an unusual emission
that we identify as CH$_{4}$ emission originating from a
very small region of the atmosphere (probably less than 100 km wide)
heated to temperatures between 750 and 1500 K and located somewhere between
10$^{-5}$ and 10$^{-4}$ bar.
In a spectrum recorded around 4.7 microns 4.5 hours after
impact L, we detect CO emissions which are not usually present. We estimate
that they are due to a local temperature enhancement of the order of 100 K
near the 2-microbar level combined with a huge enhancement in the CO abundance.
The spectrum also suggests a decrease of the temperature by at least 30 K
between the 2- and 200-microbar levels.
A more refined analysis of our observations will come from a detailed
comparison of our results with the CH$_{4}$ data of Dinelli et al. (B.A.A.S.,
vol.26, p.1582, 1994) on impact C, and the CO data of Brooke et al.
(B.A.A.S., vol.26, 1585, 1994) on impact L. Comparison with
observations at other wavelengths and different impacts will also be quite
useful.
\newpage
\begin{center}
{\bf Status of the IRTF SL/9-R Seismic Wave Search}\\[6pt]
\begin{it}
M. Marley and C. Walter\\
New Mexico State University\\[6pt]
K. Wells, D. Hunten, A. Sprague, W. Hoffmann,\\
M. Sykes, and A.Dayal\\
University of Arizona\\[6pt]
L. Deutsch \\
University of Massachusetts \\[6pt]
G. Fazio \\
Smithsonian Astrophysical Observatory \\[6pt]
J. Hora \\
University of Hawaii \\[6pt]
\end{it}
\end{center}
The search continues for seismic waves launched by the R impact
on approximately 200 $7.8\,\rm \mu$m images
of Jupiter obtained with the instrument MIRAC2 on the IRTF.
We have constructed a hodogram (an image of
mean pixel intensity as a function of angular distance from the impact
site and time) utilizing all of the IRTF data. The azimuthal averaging
substantially improves the experiment sensitivity over that
reported earlier.
Assuming a wave excitation efficiency of 15\%, our upper limit to the
impact energy of the R event is about now $4\times10^{27}\,\rm erg$.
Interestingly, this limit is comparable to that derived from observations
at the NOT telescope of the L impact employing
an order-of-magnitude more $10\,\rm \mu m$ images (Mosser {\it et al.}
European SL/9 Meeting, 1995). The IRTF experiment thus demonstrates
the power of the $7.8\,\rm \mu m$ methane band
for seismological observations of Jupiter.
\np
\bc
{\bf Galileo PPR Observations of SL9 Impact Fragments G, H, L, and Q1}\\[6pt]
\bi
Terry Z. Martin \& Glenn S. Orton\\
Jet Propulsion Laboratory\\[6pt]
\ei
\ec
The Galileo spacecraft obtained a direct view of the SL9 impacts.
High speed photometry by the PPR of SL9 fragment impacts G, H,
and L at 945 and 678 nm shows a characteristic light curve shape.
"Precursor" flashes in earthbased telescopic data imply that the
initial bolide phase was not detected by the PPR nor by the
Galileo instruments NIMS, UVS, and SSI. Thus, detected light
arises from the fireball. The sharp change in slope of the PPR
945 nm light curves after the steep initial 2 sec rise suggests
that a new opacity source developed then, due to formation of
an atomic or molecular species.
\np
\bc
{\bf Hydrogen Cyanide Polymers from the Collision
of\\
Comet Shoemaker-Levy 9 with Jupiter}\\[6pt]
\bi
C. N. Matthews\\
Dept. of Chemistry\\
Univ. of Illinois at Chicago\\[6pt]
\ei
\ec
Hydrogen cyanide polymers--heterogeneous solids ranging in color
from yellow to orange to brown to black--may be among the
organic macromolecules most readily formed within the solar
system. The non-volatile black crust of comet Halley, for example,
as well as the orange atmosphere of Jupiter, might consist largely of
such polymers synthesized from HCN formed by photolysis of
methane and ammonia. The dark brown color arising from the
impacts of comet Shoemaker-Levy 9 on Jupiter could therefore be
caused mainly by the presence of HCN polymers. Spectroscopic
detection of these predicted macromolecules and their by-products
would strengthen significantly the hypothesis that cyanide
polymerization is a preferred pathway for prebiotic and
extraterrestrial chemistry.
\np
\bc
{\bf MODELING OF THE IONOSPHERIC EFFECTS OF COMET
D/SHOEMAKER LEVY 9 IMPACTS WITH JUPITER}\\[6pt]
\bi
A. N. Maurellis and T. E. Cravens\\
University of Kansas\\[6pt]
\ei
\ec
Theoretical modeling of the Jovian ionosphere with and
without contaminant species associated with comet
Shoemaker-Levy 9 (SL9) impacts is described. Introduction
into the thermosphere of species associated with the
impacts such as ammonia, water, and hydrogen sulfide has
a dramatic effect on the ionosphere. In particular,
the ionospheric electron density can be reduced by a factor
of 100 for reasonable contaminant abundances and H3+ column
densities display increases of about a factor of 10 or so.
These ionospheric perturbations should be present over areas
of Jupiter much more extensive than the visible impact sites
due to strong thermospheric winds.
\np
\begin{center}
{\bf Recent Spectroscopic Observations of the Jovian Atmosphere\\
with the Hubble Space Telescope}\\[6pt]
\begin{it}
M. A. McGrath (STScI), R. V. Yelle (NASA/Ames),\\
K. S. Noll (STScI), H. A. Weaver (STScI)\\[6pt]
\end{it}
\end{center}
We present new spectroscopic observations of the Jovian
atmosphere made in March and April 1995 with the Hubble Space Telescope
(HST) Faint Object Spectrograph (FOS). Observations made on 3 March
1995 at the impact latitude near the central meridian using the
0.86$''$ aperture and covering the wavelength range 160--320nm show
strong NH$_3$ absorption that is significantly enhanced relative to
the pre-impact (14 July 1994) spectrum. There is no evidence for the CS$_2$
or S$_2$ absorption observed in the G impact site $\sim$4 hours after G
impact (Noll \etal, 1995). The 3 March spectrum also shows evidence for
C$_2$H$_2$ absorption, which was the only absorber clearly evident in
the pre-impact spectrum (Yelle and McGrath, 1995). FOS observations on
7 April 1995 include one spectrum obtained near the limb covering the
wavelength range 220--320nm, and three spectra covering the wavelength
range 160--230nm which map the impact latitude in the N-S direction at
$\sim$2$\degr$ latitude intervals. The limb spectrum is very similar to
pre-impact spectra, showing no evidence for the bright metallic
emissions seen near the limb close to the time of the S impact on 21
July 1994 (Noll \etal, 1995). The three spectra mapping the latitude of
impact also show strong NH$_3$ absorption, but show little evidence for
variation of the NH$_3$ with latitude. Temporal evolution of the
NH$_3$ absoprtion in spectra obtained on 14 July, 18 July, 9 August, 23
August in 1994, and 3 March and 7 April 1995 will be presented.\\
References:\\
K. S. Noll \etal, 1995. {\it Science} {\bf 267}, 1307. \\
R. V. Yelle and M. A. McGrath, submitted to {\it Icarus}, February, 1995.
\np
\bc
{\bf CASPIR Observations from Siding Spring Observatory, Australia}\\[6pt]
\bi
Peter J. McGregor \\
Mount Stromlo and Siding Spring Observatories \\
Institute of Advanced Studies \\
The Australian National University\\[6pt]
\ei
\ec
Near-infrared images of the C, D, G, K, N, R, V, and W impacts were obtained
with the CASPIR instrument on the ANU 2.3 m telescope at Siding Spring
Observatory, Australia. A selection of images from the G and K impacts
will be presented. Images at 2.34 $\mu$m provide accurate timing of the
impacts. Narrow band images in the 3--4 $\mu$m region slow the development
of an emission ring surrounding the impact sites, and a region of excess
northern auroral emission at a similar absolute latitude to the impacts.
An image at 4.78 $\mu$m taken 25 min after the K impact shows strong emission
from the impact site, indicating that the K fragment penetrated deep into
the atmosphere. This emission is not present in an image taken 45 min later.
\np
\bc
{\bf THE VERTICAL STRUCTURE OF JUPITER'S CLOUD LAYER BEFORE AND AFTER THE
IMPACT BY COMET SHOEMAKER-LEVY 9}\\[6pt]
\bi
A. V. Morozhenko, A. S. Ovsak, and P. P. Korsun\\
Main Astronomical Observatory of National Academy of Sciences of Ukraine\\
Holosiiv, Kiiv 22, 252650, Ukraine\\[6pt]
\ei
\ec
The vertical structure of Jupiter's cloud layers before
the impact (the background) and on the place of the fragment K impact
for the atmospheric pressure 0.44 $\leq$ p $leq$ 8.0 bar has been determined from
the analysis of observetional data on the spectral reflectivity in
methane absorption bands at 619, 727 and 880 nm. For the background the
maximum particle concentration (the volume scattering coefficient is
$\sim 3 \times 10^{-5} cm^{-1}$ at the 1 bar level.
The effective radius of cloud particles is approximately 1.3 micron
for p $>$ 1.5 bar. The altitude profile of the scattering component of the
effective optical depth (scattering optical depth) forms by eddy mixing
of the atmosphere. The value of vertical eddy diffusive coefficient is
$D = 0.5 \times 10^{5} cm^{2} s^{-1}$ for
p $\sim$ 1 bar or for the scattering optical depth 1-11.
Therefore the altitude stratification of particles sizes arises and
effective radius decreases from 1.3 micron ( p $=$ 1 bar), to 0.45 micron
(p $=$ 0.38 bar). Thus the contradiction is explaned between estimates of
effective radius obtained earlier from observations of linear and
circular polarization of the planet's light and especially from the
spectral dependence of the scattering optical depth. After the fragment
K impact, scattering coefficient decreased almost twice for p $\sim$ 1 bar and
increased slightly for p $<$ 1 bar. The value of D increased up to
$10^{5} cm^{2} s^{-1}$.
On the level with p $=$ 0.44 bar we have scattering optical depth
0.43. If sharp increase of D for p $<$ 0.44 bar is not assumed the
appearance of the aerosol in higher layers of the stratosphere (the
pressure up to several mbars) cannot be accounted by rising cloud
particles. Thus, the hypothesis of its origin from the comet is very
probable.
The research described in this publication was made possible in
part by Grant N U4R000 from the International Science Foundation.
\np
\begin{center}
{\bf Jovian Photochemistry Following the SL9 Impacts}\\[6pt]
\begin{it}
J. I. Moses (LPI), M. Allen (Caltech/JPL), and G. R.
Gladstone (SWRI)\\[6pt]
\end{it}
\end{center}
\medskip
The collision of SL9 with Jupiter caused many new molecular
species to be injected into the Jovian stratosphere. We use a
one-dimensional photochemical model to follow the evolution of the
impact-derived species. Sulfur photochemistry dominates the initial
evolution, but the longer-lived nitrogen and oxygen compounds also
participate in the stratospheric photochemistry. We discuss the
important photochemical processes operating on the impact-derived species,
identify the short- and long-term reservoirs of the different elements,
compare our predictions concerning the temporal variation of the major
compounds with observations, and discuss the implications for aerosol
formation and long-term observations.
\newpage
\bc
{\bf Dynamic spectroscopy of Europa before the A-impact}\\[6pt]
\bi
\framebox{H.K.Nazarchuk} and L.M.Shulman\\
Main Astronomical Observatory of the National Academy of Sciences\\
Kyiv-22, 252650, Ukraine; e-mail: shulman@mao.gluk.apc.org\\[6pt]
\ei
\ec
\begin{sloppypar}
The spectral monitoring of Europa has been carried out on
July 16, UT 19:16---20:02. The 1024-channel TV scanner at the 6-meter
telescope (Special Astrophysical Observatory of Russian Academy of
Sciences) was used. The result of the observation is the record of
the numbers of the spectral channel where one-electron event took place
each 32 msec.
The spectral range covered in one exposure is $\sim1000$\AA\
approximately centered onto H--$\beta$ line: 4400---5300\AA.
Each spectrum has been flatfield corrected and recalculated
to the wave lengths scale using the spectrum of a Ne+Ar+He lamp.
So we have got $\sim1000$ monochromatic
($\Delta\lambda\approx 1$\AA) light curves for the
above mentioned time period with a time resolution at \mbox{$\sim20$ s.}
This data can be considered like 128 sequential spectra as well.
There were no predicted impact during this time interval but the spectra
differ from the plain reflected Solar radiation slightly changed by
the albedo of Europa. Besides the Solar Fraunhofer lines
(the H$-\beta$ is the strongest) there are many weak and strong
non stationary emission peaks. Among them a strange peak is detected
at 4518\AA\ (the most probably S$^+$). It is localized
in the UT 19:46--19:50 time interval when the intensity of the 4518\AA\
emission was enhanced by the factor $\sim 2$.
It seems that H--$\beta$ emission in the pre-impact spectrum is present
too. At least there is a feature at 4861\AA\ which is either
H$-\beta$ or something else. Other possible identifications are:
O$^+$(4860.93), N$^+$(4860.35), Fe(4859.75), Ca(4859.31). All these
lines may occur in a high temperature meteor flush. Moreover,
these lines may be present in the spectrum together as well as the H$-\beta$.
Unfortunately, our spectral resolution is not good enough for
a reliable choice. This emission arose two times:
firstly at UT 19:28--19:30, and then simultaneously with
the 4815\AA\ emission.
A group of emissions is seen in the range 4920--4965\AA.
They probably belong to atoms (Fe, Ni, Na, Ca, Mg, Si),
ions (S$^+$, O$^+$, C$^+$, Ba$^+$, N$_2^+$),
and molecules (CN, O$_2$, OH, Na$_2$, H$_2$, S$_2$).
The spectrum of Europa seems to have features of a high
temperature meteor spectrum. The total
contribution of the emissions to the integral brightness of
Europa was rather small but there was detectable spectral variations
in some narrow spectral bands. It is probable that two impacts of small
undetectable fragments took place at UT 19:30 and UT 19:48. It seems
that a continuous meteor shower began approximately one hour before
the A-impact.
\end{sloppypar}
\np
\noindent\centerline
{\bf Carbon monoxide in Jupiter's stratosphere after the impact of
SL9}
\bigskip
\noindent
{\it K. S. Noll, D. Gilmore (STScI), R. F. Knacke, M. Womack, S. Fajardo
(Penn State, Behrend), C. Griffith (NAU), \& G. Orton (JPL)}
\medskip
Two lines of the CO 1-0 fundamental band were observed in Jupiter's
spectrum before and after the impacts of comet SL9 with the CSHELL
infrared spectrometer at the NASA Infrared Telescope Facility on
Mauna Kea. On the nights of August 1 and 2 (UT) the 30 arcsec slit
of CSHELL was placed parallel to latitude bands near the impact
sites at approximately 45 degrees South and at a corresponding
latitude in the Northern hemisphere. On the night of August 1 we
see no difference between CO lines at the two latitudes. On the
subsequent night, howver, we observe a distinct decrease in the
central depth of the CO R5 and R7 lines. The observations were
obtained 24 hours after the previous night's, so they sample a
different range of longitudes. On August 2 our slit includes the
fragment L impact site where strong CO emission was observed
immediately after impact (Brooke et al.~1994 BAAS 26, abstract
03.07). An explanation consistent with our observations is that
weak emission features persist and fill in the center of the CO
absorption line. We will compare model spectra to the observed CO
line profiles in an attempt to constrain the abundance of
stratospheric CO observed with this data. This is of particular
importance since it appears that CO is the primary oxygen-bearing
molecule produced by the impacts (Lellouch et al.~Nature 373, 592.,
Bjoraker private communication), though the low HST upper limit
on CO (Noll et al.~Science 267,1307.) suggests that uncertainties in the
CO vertical profile remain.
\np
\begin{center}
{\bf Jupiter's 21cm Continuum Emission caused by the Collision of Comet
\mbox{Shoemaker-Levy 9}}\\[6pt]
\begin{it}
C. A. Olano, J.C. Testori and F.R. Colomb\\
Instituto Argentino de Radioastronomia\\
C.C.5, 1894 Villa Elisa, Argentina\\[6pt]
\end{it}
\end{center}
From July 13 to August 21 we have observed Jupiter at 1420 MHz using
one of the IAR 30-m single dish radiotelescopes. After the impact of
fragment G, we detected a rapid increase of the 21cm-continuum flux,
which reached the maximum (around 20% of Jupiter's flux) at the end of
the impact period and then decayed within 30-60 days. The nature of
this radiation is clearly synchrotron, originated probably by a new
population of relativistic electrons ( 1.E28 -1.E29) injected into the
Jovian magnetosphere. The energy released by the explosions under the
form of relativistic electrons is of 1.E22-1.E23 erg. The decay time
of the flux density, when interpreted as due to synchrotron losses,
implies that the relativistic electrons were subject to a mean
magnetic field of 3-5 G. However, non-synchrotron losses can better
account for the magnitude of the losses required by the data.
\newpage
\begin{center}
\Large
{\bf Cloud perturbations as a result of the SL9 impacts}
\end{center}
\normalsize
\begin{center}
J.L. Ortiz$^*$, G. Orton, K. Baines, P. Yanamandra-Fisher, J. Friedson. \\
Jet Propulsion Laboratory, Pasadena, CA 91106\\
T.H. Herbst\\
Max Planck Institute f\"ur Astronomie, Heidelberg, Germany\\
D.P. Hamilton\\
Max Planck Institute f\"ur Astronomie, Heidelberg, Germany\\
H. B\"onhardt\\
Universitaets-Sternwarte, M\"unchen, Germany\\
\vskip 0.5truecm
*also at the Instituto de Astrofisica de Andalucia, CSIC, Spain\\
ortiz@uli.jpl.nasa.gov ~ ortiz@iaa.es \\
\end{center}
\vskip 0.5truecm
The normal Jovian vertical structure was affected by the formation of a
very dark haze at visible/uv wavelengths, mostly at stratospheric and
upper tropospheric levels, but the perturbations at deeper levels are
still uncertain. We present the first efforts to address this topic,
by analyzing some imaging and spectroscopic results from Calar Alto in
the range 1 to 2.5 $\mu$m on several impact areas along with IRTF mid-IR
images for the same impact sites. Changes in molecular equivalent
widths are investigated in the near IR as well as changes in cloud
opacity for longer wavelengths.
\np
\bc
{\bf Spatial Variation and Time Dependence of
the Temperature Structure of Impact Sites}\\[6pt]
\bi
Glenn Orton\\
Jet Propulsion Laboratory\\
California Institute of Technology\\[6pt]
Joseph Spitale\\
California Institute of Technology\\[6pt]
James Friedson, Padma Yanamandra-Fisher, Kevin Baines\\
Jet Propulsion Laboratory\\
California Institute of Technology\\[6pt]
William Hoffmann, Aditya Dayal\\
Steward Observatory\\
University of Arizona\\[6pt]
Lynne Deutsch\\
Five-College Astronomy Department\\
University of Massachusetts\\[6pt]
Joseph Hora\\
Institute for Astronomy\\
University of Hawaii\\[6pt]
\ei
\ec
The NASA Infrared Telescope Facility comet crash program included an
investigation of temperature structure at the impact sites. This experiment
used the MIRAC2 mid-infrared array camera to image Jupiter at several
wavelegnths where thermal emission was dominated by well mixed constituents:
CH$_4$ at 7.8 $\mu$m to sense stratospheric temperatures near 8 mbar and H$_2$
at 13.0, 17.8, 20.2 and 20.8 $\mu$m to sense tropospheric temperatures between
150 and 400 mbar. We present temperature sounding results from absolutely
calibrated observations which show the vertical variability of temperature
as a function of time, concentrating specifically on the region near the K
impact site.
\np
\bc
{\bf HST FAINT OBJECT CAMERA UV OBSERVATIONS OF THE SHOEMAKER-
LEVY 9 IMPACT SITES AND OF THEIR TEMPORAL EVOLUTION}\\[6pt]
\bi
R. Prang\'e \& C. Emerich (IAS/CNRS, Orsay, France)\\
D. Rego (IAS, Orsay, France and U. Michigan, USA)\\
F. Paresce (STScI, Baltimore)\\[6pt]
\ei
\ec
Images of Jupiter have been taken in the UV with the Hubble Space
Telescope Faint Object Camera (FOC) from July 13, 1994, before the
beginning of the comet fragment infalls, to August 9, 1994, more than
two weeks after the end of the event. The camera was used with FUV
filters centered on the H$_2$ bands, collisionally excited in the high
latitude aurorae, around 1500 \AA. The solar flux reflected by the
atmosphere of Jupiter was also transmitted in the long wavelength wing
of the transmission function. When folded with a Jovian reflected
spectrum, the FOC transmitted flux peaks near 2000 \AA $ $, and covers
the 1700 to 4000 \AA $ $ range. Therefore, the altitude range studied
is higher than in visible images.
The core of fresh impact sites is darker and more extended than the
streak seen in visible images, and it is surrounded by an extended area
(several arcsec), also larger and darker than the visible plumes. They
are very similar to features observed with WFPC2 in the FUV, although
less dark on average. This is consistent with the difference in
altitude range sampled, and can be used for a comprehensive diagnostic
of the plume material.
Two images, taken on August 9, on both sides of Jupiter, show the long
term evolution of the UV absorbing material in the upper
stratosphere/thermosphere. The evolution is very different depending on
the fragments, some of the plumes (as A) have almost disappeared
whereas others (the major ones) are still very dark (up to 70\%
absorption). In addition to longitudinal drift of the material in the
stratosphere creating a belt-like feature, we identify a strong
latitudinal diffusion with significant absorption from the auroral zone
up to the edge of the FOC frame ($\simeq$ 20-25 $^circ$). Finally
transient and/or meridional winds in the upper stratosphere are
inferred from the observation of several structures drifting north of
the impact region. This also is consistent with results obtained from
FUV WFPC2 observations.
\newpage
\bc
{\bf MAGNETIC MAPPING AND INTERPRETATION OF AURORAL SIGNATURES
OF COMET SL9 IN THE JOVIAN MAGNETOSPHERE}\\[6pt]
\bi
R. Prang\'e (IAS, Orsay, France)\\
I. Engle (Naval Academy, Annapolis, USA)\\
M. Dunlop \& M.K. Dougherty (Imperial College, London, UK)\\
S. Maurice (ESTEC, Nordjwick, Netherlands)\\
W. H. Ip (MPI, Lindau, Germany)\\
J.T. Clarke \& G.E. Ballester (U. Michigan, USA)\\[6pt]
\ei
\ec
Before impacting the dense atmosphere of Jupiter, the fragments of
comet Shoemaker- Levy 9 spent a few days flying across its
magnetosphere (several millions of km across). Electrodynamic
interaction with the ambient plasma induced several unique phenomena
detected in the UV, X ray and radio wavelength ranges.
Among them, the detection of an unusual 'blinking' UV bright spot in
Hubble Space Telescope images of the southern polar cap on July 20,
just before P2 collision, might be attributed to auroral type processes
triggered by the charged environment of the comet fragments, as
described in some prediction models. A detailed modeling of the time
varying morphology of the magnetic field lines enables us to compare
the location of this spot with the magnetic footprint of the fragments
still in the magnetosphere, and to determine the characteristics of the
corresponding field line. We show that fragment Q is a good candidate,
and we discuss whether the data can allow us to distinguish between the
various fragments.
We establish also that Q was on an open magnetic field line at the time
of the observations, in agreement with the lack of observable conjugate
emission from the north, although the most distant fragments may be on
closed field lines. We study the deformation of the instantaneous Q
magnetic field line in the hours following the UV observations, to
investigate a later set of images and any possibility of relationship
between this UV event and a close-in-time X ray emission from the
northern hemisphere. We find that the field line passing through Q
closed during two periods before the fragment impacted the atmosphere,
the first one corresponding to the north X ray burst and to the second
set of UV images.
Under the assumption that this auroral emission is indeed a signature
of the interaction of the coma of fragment Q with the magnetosphere,
and that this interaction is triggered by a mechanism alike the one
predicted in Ip and Prang\'e (1994) which involves field-aligned
currents, we propose an explanation of the modulation of the spot
brightness.
\np
\begin{center}
{\bf On the Disappearance of the Dark Band in the Jovian Southern Hemisphere
before the SL9 Impacts on the Planet}\\[6pt]
\begin{it}
PROKOF'EVA V.V.\\
Crimean Astrophysical Observatory\\[6pt]
TARASHCHUK V.P., CHURYUMOV K.I.\\
Astronomical Observatory of Kiev University\\[6pt]
\end{it}
\end{center}
It is known that Jupiter disc is rich in numerous details. Some
of them change their contours appear and disappear within small
time intervals. Other details, though they can suffer several
changes, remain for month, years, centuries. They all are purely
atmospheric formation because Jupiter does not have hard surface.
As usual during falldown of fragments of comet Shoemaker-Levi 9
on Jupiter dark bands and light zones between them were observed.
However blurring and later disappearance of the dark band in the
southern hemisphere were observed. This phenomena occurred before
fall down of 21 secondary nuclei, i.e. it took place before
July 16 1995. After their fall down on to the visible surface of
the planet dark formation, on which the spectrograph diaphragm
have been guided. The principal components of the Jupiter
atmosphere are hydrogen H2, helium He, methane CH4, in the
gaseous state and ammonium NH3 in form of aerosol of the cloudy
sheet, comprising small crystals as well as product of their
dissociation as the result of photochemistry processes (C2H2 -
acetylene, N2H4 - hydrazine et al.) yield the most powerful
absorption bands in the visible range of the spectrum: 619, 725
nm - methane, 644.1 , 790 nm - ammonium). Sharp contours of the
dark features are connected with methane, while NH3 yields more
light clouds located higher and having lower temperature.
Intensities of bands of methane and ammonium is dependent not
only from their abundance but to a greater extent from the
physical conditions in the atmosphere. Possible mechanism of the
disappearance of the dark band in the Jupiter south hemisphere is
discussed.
\newpage
\begin{center}
{\bf Pre-impact Images of Comet \mbox{P/Shoemaker-Levy 9} from Las
Campanas}\\[6pt]
\begin{it}
David L. Rabinowitz\\
Carnegie Institution of Washington, Department of Terrestrial Magnetism\\
5241 Broad Branch Rd, NW, Washington, DC 20015\\[6pt]
\end{it}
\end{center}
On the night of 1994 July 16 (~04:00 UT), visible light images of nuclei
E, G, L, P2 (8a and 8b) , Q1, Q2, R, S, and W of comet P/Shoemaker-Levy 9
were obtained using a CCD and coronagraph at 100$"$ Dupont Telescope of
Carnegie Observatories (Las Campanas, Chile). The coronagraph was built by
Steve Larson (University of Arizona) as part of the Comet Impact Network
Experiment [1, 2]. Each of nuclei E, G, L, Q(1,2), and W show trails of
material extending towards Jupiter. Similar trails appear in Hubble Space
Telescope images of the "P-Q complex" on July 20 UT, but not on July 11 UT
and prior images. Because these trails extend asymmetrically from the
nuclei, it is unlikely that Jovian tidal forces can explain their
appearance. Other forces, such as Lorentz drag in the the Jovian magnetic
field, may be responsible.\\
[1] S. Larson et al., 1994, The Comet Impact Network Experiment, BAAS 26.\\
[2] J. Scotti et al., 1994, Preliminary Results from The Comet Impact
Network Experiment, BAAS 26.
\np
\bc
{\bf Deep Coma Imaging of Comet Shoemaker-Levy 9 to Characterize Dust Outflow
Velocities and Grain Sizes}\\[6pt]
\bi
T. W. Rettig, J. Hahn, \& G. Sobczak\\
Univ. Notre Dame\\[6pt]
M. J. Mumma\\
NASA/Goddard\\[6pt]
\ei
\ec
The comae resulting from the approximately 20 fragments of Comet
Shoemaker-Levy 9 present a unique opportunity to characterize the ejected
cometary dust grains that were once buried deep within the parent
progenitor. We present an analysis of the spatial brightness profiles of
P/S-L 9's inner comae extracted from Hubble Space Telescope images obtained
from January through July 1994. These profiles reveal that most of the S-L
9 fragments exhibit the usual r$^{-1}$ spatial dependence in their inner
r $\leq 1''$
comae in observations where jovian tides are unimportant. Beyond this
distance, the comae lose their circular appearance as radiation pressure
drives the dust tailward. This distance is related to two unknown
properties of comet dust grains: the grain size and outflow velocity. But
when the comet fragments are within about 100RJ of Jupiter, where RJ is one
Jupiter radius, jovian tides become the dominant perturbation acting on the
comae. However, the projected distance beyond which tides distort the
comae are related only to a single unknown, the dust outflow velocity.
Thus, by measuring the distance beyond which the comae are initially
distorted by radiation pressure, and in later observations by tides, we are
able to extract an estimate of the characteristic dust grain size, which is
of order 10 to 100 microns, and its outflow velocity ~3 meters/sec. In
comparison to gas driven cometary outflows measured in other comets, the
emitted dust grains leaving the P/S-L 9 fragments are unusually large with
considerably lower velocities. In addition to the dust sizes and
velocities, the surface brightness profiles will be used to extract the
central brightness excesses which are a measure of the reflecting area in
the inner comae regions. We will also present the temporal magnitude
variations of the inner comae regions. These observations are being used
in conjunction with tidally distorted Monte Carlo models to place
constraints on the dust outflow velocities and dust production rates.
\np
\bc
{\bf Evolution and Drift of the Visible Impact Scars}\\[6pt]
\bi
John Rogers\\
British Astronomical Association\\[6pt]
\ei
\ec
Most of the visible SL9 impact sites lasted more than a month, and
their average rotation period was very close to that of the S.S.S.
Temperate Current or System III. However, there was evidence for
diverse local motions. At first, the black core regions had an average
System III drift of +6 deg/month (+/- 5, s.d.) (omitting the multiple
impact sites K/W and D/G/S). But the leading edges, peripheral
clouds, and whole sites later, moved faster: -10 deg/month (+/- 12,
s.d.), which is faster than the underlying cloud-top currents. By
mid-September the sites had merged into an uneven new belt. In early
1995, this belt was still present but fading.
\np
\bc
{\bf Normal Patterns of Dark Spots in Jupiter's Atmosphere}\\[6pt]
\bi
John Rogers and Michael Foulkes\\
British Astronomical Association\\[6pt]
\ei
\ec
The SL9 impact scars were unprecedented in the experience of visual
observers of Jupiter. All available observations of Jupiter have been
surveyed (J.R., The Giant Planet Jupiter, CUP, 1995). The record is
complete from 1878 onwards. Almost all dark spots are of recognisable
types in fixed latitudes moving on permanent currents. There are no
outstanding records of large black sudden-onset spots like impact
sites G or L. Therefore the frequency of such impacts (allowing for
unoservability during solar conjunction) is less than one per 70
years.
\np
\bc
{\bf Atomic Line Emissions in the Impacts of Comet SL-9 into Jupiter}\\[6pt]
\bi
M. Roos-Serote, A. Barucci, J. Crovisier, P. Drossart,\\
M. Fulchignoni, L. Lecacheux and F. Roques\\[6pt]
Observatoire de Paris-Meudon\\[6pt]
\ei
\ec
High-resolution spectroscopy of Jupiter was performed during and
after the impacts of comet SL-9 at the Pic du Midi 2-m telescope. Spectra
with a resolving power of 36,000 between 564 and 875 nm were recorded with
the MUSICOS (MUlti SIte COntinuous Spectroscopy) spectrograph. Transient
emissions of atomic lines following impacts L and Q1 were detected: sodium
(589 nm doublet), iron (multiplets at 804, 636 and 550 nm), calcium (657 nm
intersystem line and 616 nm triplet), lithium (671 nm doublet), potassium
(766 nm line) as well as the hydrogen H alpha line. These lines were
detected about 15 min after the impacts and were no longer visible one hour
after.
The excitation process for these atomic emissions is not yet
understood in every detail. The resonant fluorescence mechanism can neither
account for the observed intensities nor for the presence of the Ca
intersystem line. Collisional excitation is not efficient at the high
altitudes reached by the plumes. The falling back of the plumes at a
velocity of 10 km/s on Jupiter might explain the transient emission.
Electronic recombination processes and chemical reactions might also play a
role.
The alkali and metals observed are not usually present in Jupiter's
upper atmosphere and should come from the refractory compounds of the comet
nucleus. Correct modelling of the excitation processes of the emission
lines will allow the determination of the abundances of these species in
the comet.
\np
\bc
{\bf DISRUPTION OF SL9 BY VOLATILES RELEASED BY TIDAL HEATING}\\[6pt]
\bi
T.V. Ruzmaikina\\
Lunar and Planetary Laboratory\\
University of Arizona, Tucson 85721\\[6pt]
\ei
\ec
The comet Shoemaker-Levy 9, revealed in March of 1993 as a
string-of-pearls of 21 major fragments, has been destroyed
when it passed Jupiter within Roche limit,
at the distance about 1.6 of the planet's radius in 1992.
In this paper we suggest an idea that the comet might had been
disrupted not by the tidal force itself, but by the pressure of
volatiles released due to the tidal heating.
We consider the comet as a conglomeration of blocks divided by
narrow "fracture" zones, and assume that the tidal force initiated
the sliding of parts of the comet along one (or few) zones.
Then the heat released in a narrow shear layer between the blocks
could be sufficient for the evaporation of highly volatile
elements and their pressure could disrupt the comet.
The momentum transferred to the pieces of the comet
is large enough to provide them velocities exceeding escape
speed from the surface of the comet and hence prevent their
coalescence, provided that the comet radius was $< 10$ km.
We speculate that the shear induced release of volatiles
could also cause disruption of the comet fragments
in the upper layers of Jovian atmosphere, and thus
explain the shallow penetration of the fragments without
putting a strong restriction on their sizes.
\np
\bc
{\bf MORPHOLOGY AND MOTIONS OF THE SL9 IMPACT
CLOUDS\\
(JULY 1994-APRIL 1995)}\\[6pt]
\bi
A. Sanchez-Lavega (1), J. Lecacheux (2), F. Colas (3), J. M. Gomez (4),
P. Laques (5), I. Miyazaki (6), and D.C. Parker(7)\\[6pt]
\ei
\ec
\bi
(1) Dpto. Fisica AplicadaI, Universidad Pais Vasco, Bilbao, Spain.\\
(2) DESPA, Obs. Paris-Meudon, France.\\
(3) Bureau des Longitudes, Paris, France.\\
(4) Grup d'Estudis Astronomics, Barcelona, Spain.\\
(5) Observatoire Pic-du-Midi, Bagneres-de-Bigorre, France.\\
(6) Oriental Astronomical Association, Okinawa, Japan.\\
(7) Association Lunar Planetary Observers, Florida, USA.\\[6pt]
\ei
A large number of CCD images of the SL9 impact clouds in the wavelength
range 600-900 nm, taken at Pic-du-Midi Observatory in France from July
1994 to April 1995, has allowed us to study the morphological changes and
motions of the impact clouds. Our measurements show the existence of at
least three different kind of motions (July-August 1994): (1) Eastward
expansion during the first two days of the largest impact regions (K, L,
G) with velocities in the range from 36 to 60 m/s; (2) Clouds that acted
probably as passive tracers of the stratospheric flow (velocities in the
range -15 to 20 m/s); (3) Local motions of the cloud elements with
meridional components, sometimes related to the interaction with
anticyclonic ovals in nearby latitudes (velocities of about 20 m/s). The
average zonal velocity relative to System III of the cores of impacts E,
A, C, W, K, L, G, R, Q1 and H was (up to August 18) -1.7 m/s with an
average jovicentric latitude of -43.8 deg. Since mid-August and up to early
October 1994, the preferentially zonal spreading of the clouds formed a
nearly complete belt at latitude -44.6 deg together with scattered clouds
alongside parallels -55.0 and -36.2 deg. Post-solar conjunction
observations between January and April 1995, show the permanence of the
heterogeneous dark belt at -44 deg which contains numerous local
condensations (size 3000-10000 km) dispersed along the whole latitude
circle. Other synoptic clouds, probably pertaining to the SL9 impact,
were detected at -54 deg during this period.
\np
\bc
{\bf Comet Shoemaker-Levy 9 in Historical Context:\\
The Record of Split Comets on the Galilean Satellites}\\[6pt]
\bi
Paul M. Schenk (LPI, Houston, TX), Erik Asphaug (NASA ARC, Moffett Field, CA), William B. McKinnon (Wash. U., St. Louis, MO), H.J. Melosh (LPL, U. of Ariz., Tucson, AZ), and Paul Weissman (JPL, Pasadena, CA)\\[6pt]
\ei
\ec
Shortly after discovery of comet Shoemaker-Levy 9 in 1993, Melosh and
Schenk concluded that crater chains on the Galilean satellites Callisto
and Ganymede were the result of the impact of past split comets. We
investigate the morphology of crater chains, focusing on three key
problems:
\begin{itemize}
\item What are the gross physical properties (e.g., mass, radii)
of Jupiter-family comets?
\item What are the characteristics of individual fragments at the time
of impact?
\item What is the nature of the breakup process: can we distinguish between
'rubble piles,' 'solid' snowballs and other breakup models?
\end{itemize}
We compare these properties with those of Shoemaker-Levy 9, providing a
historical context in which to evaluate that event.
\np
\bc
{\bf COLLISION OF COMET \mbox{SHOEMAKER-LEVY 9} WITH JUPITER: IMPACT STUDY OF
TWO FRAGMENTS FROM TIMING OF PRECURSOR EVENTS}\\[6pt]
\bi
Zdenek Sekanina\\
Jet Propulsion Laboratory, California Institute of Technology\\
Pasadena, California 91109, U.S.A.\\[6pt]
\ei
\ec
The impacts of fragments K and R of comet Shoemaker-Levy 9 are
investigated with the aims to interpret the timing of the observed
precursors to the main thermal emission event and to correlate the
results of ground-based infrared observations with a variety of
observations made onboard the Galileo space- craft. Analysis of the
phenomena associated with the impact and explosion of fragment K shows
that there is no discrepancy in the timing of the Earth- and
Galileo-based observations and that the time of \mbox{53 $\pm$ 3}
seconds between the emission peak of Precursor 1 and the onset of
Precursor 2 can be interpreted as the interval between the impactor's
disappearance behind the Jovian limb and the first appearance of the
ejecta's plume over the limb following the explosion of the impactor's
residual mass, as viewed by terrestrial observers. It is concluded
that the impactor exploded at an altitude of 45 to 50 km above the
pressure level of 1 bar and that the residual mass involved in the
explo- sion, approximately 6 to 7 million tons and about 400 meters
across, repre- sented only a fraction of 1 percent of the fragment's
preatmospheric mass. The explosion is calculated to have taken place
under a dynamic pressure of several hundred bars and the dissipated
energy is found to have been on the order of \mbox{10$^{26}$ erg}. The
results for fragment R show it to be smaller and less massive than
fragment K, exploding slightly higher in the Jovian strato- sphere,
50-60 km above 1 bar. The preferred solutions suggest that the rate of
ablation of these impactors was comparable with, or somewhat higher
than, that of category IIIb fireballs in the Earth's atmosphere. These
fireballs represent a population of objects consisting of "soft"
cometary material, whose bulk density is typically \mbox{0.2 g/cm$^{3}$}.
Preliminary evidence from other observations of the
various fragments appears to be consistent with the pres- ent
conclusions. All plume-expansion models based on penetrations below
the clouds are incorrect and need major revisions. The successful
prediction of explosion altitudes for the \mbox{Shoemaker-Levy 9}
fragments, based on the slightly modified fundamental equations of the
classical theory of meteor physics and on ablation rates derived from
data on relevant terrestrial fireballs, is a tribute to the meteor
theory and demonstrates the versatility of its tech- niques in
applications.
\np
\bc
{\bf SAAO K-band Imaging Observations of the Collision of\\
Comet \mbox{P/Shoemaker-Levy 9} and Jupiter}\\[6pt]
\bi
Kazuhiro Sekiguchi (NAO-Japan \& SAAO), Ian S Glass (SAAO),\\
and Satoru Takeuchi (Kyusyu Univ.)\\[6pt]
\ei
\ec
We present results of K-band imaging observations of the collision of
Comet \mbox{P/Shoemaker Levy 9} obtained using the
SAAO/U-Tokyo/NAO-Japan PtSi IR camera on the 75-cm telescope at the
SAAO Sutherland. Time resolved (30 sec and 10 sec interval)
observations of the impacts by the fragments, A,E,H,P2,Q1,Q2,S and T
were analyzed and K-band light curves of the each impact event have
been constructed.
\np
\bc
{\bf Interaction between the magnetospheres of comet SL9 and Jupiter}\\[6pt]
\bi
A. S. Sharma, G. M. Milikh and A. S. Lipatov\\
Department of Astronomy\\
University of Maryland\\
College Park, Maryland\\[6pt]
\ei
\ec
The plasma in the cometary magnetosphere formed by the mass loading of
the solar wind by the cometary ions is tenuous and has low energies
at 5 AU. Simulations using hybrid (particle ions and fluid electrons)
plasma simulation codes have given plasma density of 2--3 cm-3 and
electron temperature of a few eV in the cometary bow shock region.
The interaction of the Jovian and cometary magnetospheres, simulated
with these codes, yields local enhancements of the magnetic field and
plasma density by a factor of 4 -- 5 and the electron temperature by
2-- 3. Enhancement in the intensities of the ion emissions in this
region was predicted at the SL9 - Jupiter encounter and the HST/FOS
observations have shown a strong MgII 280 nm emission at 53 RJ from
Jupiter. The detailed modeling of the emissions and its implications to
the magnetospheres at the interaction will be presented.
\np
\bc
{\bf Global Maps and Drift Rates for Jovian Features}\\[6pt]
\bi
Simon, A. A., Beebe, R. F., \& Chanover, N. J.\\
New Mexico State University\\[6pt]
\ei
\ec
Using Hubble Space Telescope Cycle 4 data obtained on February 13, 1995 with
WFPC2, a maximum resolution global map of Jupiter has been constructed at a
wavelength of 410 nm. This map can be compared to a similar map produced from
images taken after the Comet P/Shoemaker-Levy 9 impacts on July 23, 1994.
Standard features have been tagged on the February 13th map, and their drift
rates computed. This is important in studying cloud morphologies and transient
features on Jupiter. In addition, interacting features have been tagged on the
impact map and their circulation rates determined.
\np
\bc
{\bf Radio Observations of Jupiter from HartRAO}\\[6pt]
\bi
D.P. Smits \& G.D. Nicolson\\[6pt]
\ei
\ec
Monitoring of Jupiter's microwave emission at wavelengths of 18, 13, 6 and 3.6
cm commenced at the Hartebeesthoek Radio Astronomy Observatory (HartRAO) a few
weeks prior to the collision of the fragments of comet Shoemaker-Levy 9 into
the planet, continued daily during the week of impacts and irregularly
thereafter. Short-timescale 6 cm and 3.6 cm data collected during the times
of 2 impacts show no observable changes. The horizon-to-horizon runs recorded
during the week of impacts show a gradual flux increase. The largest increases
occurred at 18 and 13 cm suggesting that the synchrotron emission has
increased. Monitoring of the fluxes after the collisions shows that they have
remained in their high state. The analyzed data will be presented together
with recent radio data (1995) from Jupiter collected at HartRAO.
\np
\bc
{\bf Near-IR Images and Spectra of the Impact Sites from Cerro Tololo}\\[6pt]
\bi
John R. Spencer (Lowell Observatory), Darren L. DePoy (Ohio State University),\\
Glenn S. Orton (JPL), Christophe Dumas (University of Hawaii),\\
Sang J. Kim (University of Maryland)\\[6pt]
\ei
\ec
We used the 1 - 2.5 micron Ohio State Infrared Imager Spectrometer
(OSIRIS) to observe the Shoemaker-Levy 9 impacts from the CTIO 4-meter
telescope in Chile. We obtained 1.58, 1.7, and 2.3 micron images and
1-2.5 micron cross-dispersed R=500 spectra of the impact sites during
the following times in July (given in fractional days): 16.95--17.15;
17.93--18.15; 19.00; 22.80--22.90; and 23.18; also a few images near
days 25.0 and 27.0. Continuous movies at 1.7 or 2.3 microns during
the B and F impacts showed no detectable effects due to these events,
though clouds caused brief interruptions, and all other impact events
were clouded out.
2.05 - 2.30 micron spectra of the impact site clouds show CH4
absorption, presumably due to CH4 above the impact clouds: simple
reflecting-layer models assuming normal atmospheric CH4 abundances
above the impact sites give cloud altitudes in the 1 mbar range,
though there is considerable variation in the strength of the CH4
bands between impact sites of the same age: the D site shows much
stronger overlying CH4 absorption than the E site when both are 0.48
days old, for instance. There is very little CH4 absorption above the
A site at age 0.17 days. Spectra of the E site appear to show that
the ``halo'' around the site was at a higher altitude than the central
``core''. In contrast to visible continuum wavelengths
where the impact sites appeared dark, the sites were invisible at
the near-infrared continuum wavelength of 1.58 microns.
Follow-up imaging of the impact sites from the IRTF in September
1994, February 1995, and March 1995 showed that considerable
structure persisted in the impact-generated clouds even eight
months after the impacts.
\np
\bc
{\bf Measurements of Water in the `Re-entry phase' Following
Fragments R and W of Comet Shoemaker Levy 9}\\[6pt]
\bi
A.L. Sprague$^1$, G.L. Bjoraker$^2$, D.M. Hunten$^1$, F.C. Witteborn$^3$,
R.W.H. Kozlowski$^3$, and D.H. Wooden$^3$\\[6pt]
\ei
\ec
\bi
$^1$ LPL, The University of Arizona\\
$^2$ NASA GSFC \ $^3$ NASA ARC\\[6pt]
\ei
We have measured the abundance of water seen in spectra following
the R and W impacts of Comet Shoemaker Levy~9
into Jupiter's upper Atmosphere. Measurements were made with
HIFOGS on board the Kuiper Airborne Observatory that flew out
of Melbourne, Australia on July 21 and 22, 1994.
The 6.6 $\mu$m \ band of high quantum number rotational states
was seen for approximately 5 minutes following both impacts.
Abundances are: $\sim$ 5.7 $\times$ 10$^{10}$ \ g for
R+12 minutes and $\sim$ 2.2 $\times$ 10$^{10}$ \ g\ for W+10 minutes.
These masses are equivalent to ice balls of diameter 50 and 35 m
respectively.
If we accept the Galileo NIMS conclusion that the
explosion of R occurred near the 0.2 bar level then
the water is from the bolide rather than the Jovian
atmosphere.
\np
\bc
{\bf Polarimetric Imaging Observations of Impact Dark Spots}\\[6pt]
\bi
B. Suzuki, J. Watanabe, T. Sasaki and H. Kurihara\\[6pt]
\ei
\ec
We carried out a polarimetric observation of traces of the comet
impacts on 20th July 1994 with OOPS(Okayama Optical Polarimetry System)
attached to the 91cm reflector at Okayama Astrophysical Observatory.
The measurements of the degree of linear polarization fragments K and L
sites were obtained with four wavelength range(514, 644, 659 and 820nm).
The trend of maximum polarization degree of impact dark spot appears
about 4 percent which is higher than the Jovian atmosphere situated equal
latitude. Wavelength dependence of polarization is not known well from
our preliminary results.
\np
\bc
{\bf NUMERICAL SIMULATIONS OF IMPACT OF COMET SHOEMAKER-LEVY 9:
COMPARISON WITH OBSERVATIONAL RESULTS}\\[6pt]
\bi
T. Takata\\
Univ. of Tokyo\\
JAPAN\\[6pt]
T.J. Ahrens \& J.D. O'Keefe\\
Caltech\\
Pasadena CA 91125\\[6pt]
G. S. Orton\\
JPL\\
Pasadena CA 9110\\[6pt]
\ei
\ec
Numerical simulations of impact of fragments of SL9 were conducted
to predict the impact phenomena and the observational possibilities
[Takata et al., 1994, Ahrens et al., 1994(1)(2)].
These results are compared with observational results,
such as chemical abundance and plume heights (Hammel et al., 1995,
Carlson et al., 1995) to investigate the nature of SL9 fragments such
as the progenitor size and the origin of the parent body.
The comparison suggests that the material of SL9 is primitive,
and that sizes of a large fragment and the parent body are $\sim$2 and
$\sim 4-5$ km in diameter, respectively.
\np
\bc
{\bf The OAO near-infrared observations of the SL-9 impact to Jupiter}\\[6pt]
\bi
Satoru Takeuchi\\
Department of Physics\\
Kyushu University\\[6pt]
Hitoshi Hasegawa\\
Astec, Inc.\\[6pt]
Jun-ichi Watanabe and Takuya Yamashita\\
National Astronomical Observatory of Japan\\[6pt]
\ei
\ec
We observed the impact of comet Shoemaker-Levy 9 into Jupiter by 188cm
telescope of Okayama Astrophysical Observatory with a near-infrared
camera, OASIS. Flashes originated to the impacts of fragments C,D and
K were detected at wavelength of 2.35 micron. We report the detail of
these observations and discuss some impact phenomena.
\np
\bc
{\bf Was SL-9 a Jupiter Family Comet or an Escaped Asteroid?\\
(Dynamical Considerations)}\\[6pt]
\bi
Gonzalo Tancredi and Andrea Sosa\\
Depto Atronomia, Fac. Ciencias\\
Montevideo, Uruguay\\[6pt]
\ei
\ec
SL-9 was an unusual object in many senses. Despite the fragmentation and
collision with Jupiter, the dynamics of SL-9 were remarkable. SL-9
experienced a long-lasting temporary satellite capture by Jupiter. The
duration of the encounter can not be unequivocally determined due to the chaotic
character of the motion, but the evolution can reliably tracked for more than
20 years. There are only two other objects which had suffered comparative but
much shorter satellite capture: P/Helin-Roman-Crockett and P/Gehrels 3.
Long-lasting satellite captures are a rare phenomena among the observed Jupiter
family comets, because there is a very narrow window in the orbital elements
phase-space for which it can occur.
A useful parameter to classify the candidate orbits is the Tisserand
parameter (T), an integral of motion in the Restricted Three Body
Problem. Values of T $\sim$ 3 are needed for long-lasting captures. In
fact, SL-9 and the two objects mentioned before have T $\geq$ 3. There
are also two large populations of objects with T $\sim$ 3, i.e. the
Trojan and the Hilda asteroids; but the mean motion resonances with
Jupiter (the 1:1 and 3:2 respectively) act as a protection mechanism
that prevents the close encounter. Nevertheless, due to mutual
perturbations or collisions, an asteroid can escape from the resonance
and become a Jupiter approacher.
We compare the probability for objects in the three groups to experience a
longlasting satellite capture and estimate the frequency of collision with
Jupiter.
\np
\bc
{\bf THE REFLECTIVITY OF THE AEROSOL MATERIAL IN THE G, L AND E
IMPACT-REGIONS}\\[6pt]
\bi
Tejfel V.G., Kharitonova G.A., Sinyaeva N.V.,\\
Gajsina V.N., Aksenov A.N., Kirienko G.A.\\
Fessenkov Astrophysical Institute, Kazakhstan National\\
Academy of Sciences, Alma-Ata, 480068 , Kazakhstan\\[6pt]
\ei
\ec
The consequences of the Comet Shoemaker-Levy and Jupiter collisions
(CJC) were observed photographically during 16 nights between 17 July
and 15 August 1994 with the 1-meter telescope in the high mountain
Assy observatory (80 km eastern Alma-Ata, altitude 2750 m). 150
photographic images obtained with the scale 1.8 arcsec/mm were
measured on automatized microdensitometer. Computerized images were
analyzed to find the planetographic coordinates of the dark
impact-regions, their sizes and relative intensities in the blue and
red light. The best images (24 and 25 July) in blue and red light with
the impact-regions G, L and E placed near the central meridian were
studied especially to estimate the minimum relative intensities at the
centers of these regions. These intensities are not less 0.62, 0.64
and 0.72 for G,L and E regions respectively on the original images and
cannot be less than O.2-0.5 if the smoothing will be considered. The
modeling calculations for the most probable characteristics of the
cometary solid material that has low albedo have given the estimates
of the optical depth for the stratospheric layer formed by dark
cometary material. For assumed law of the radial distribution of the
dark material amount within observed area of the inpact-regions the
sizes of the cometary fragments are derived. They cannot exceed
0.2-0.3 km and this estimate don't contradict to the values derived
from other considerations.
\np
\bc
{\bf High temporal resolution near-IR observations of impacts H and Q
from Calar Alto and interpretation}\\[6pt]
\bi
G.P. Tozzi, A. Richichi, \& A. Ferrara\\
Osservatorio Astrofisico di Arcetri\\[6pt]
\ei
\ec
Observations with a fast IR photometer at the 2.2m telescope on
Calar Alto have yielded high temporal resolution (sampling
typically 100~Hz) lightcurves for some of the impacts, including
A, H, Q1/Q2, T (Richichi et al. 1995).
In this contribution, we analyze in some detail the data for
the main impacts in this set, namely H and Q1. By comparing
our H data with those available at other wavelengths, we present
estimates of the temperature of the phenomenon and its evolution.
In the case of Q1, it is particularly interesting to examine the
fine structure of the lightcurve, which is generally lost in
other observations available at lower temporal resolution.
\newpage
\bc
{\bf FUV Spectra of SL9 Impact Site G with HST/GHRS}\\[6pt]
\bi
L. M. Trafton, S. K. Atreya, M. A. McGrath, G. R. Gladstone,\\
J. J. Caldwell, K. S. Noll, H. A. Weaver, R. V. Yelle,\\
C. Barnet, and S. Edgington\\[6pt]
\ei
\ec
Spectra using grating G140L obtained within hours of the impact of
fragment G of comet SL9 with Jupiter are presented at effective
resolution $4.4$ \AA . Below 1610 \AA\ the spectrum is dominated by
emission, with Io's torus being tilted largely out of the field of
view. The H$_{\rm 2}$ dayglow spectrum is analyzed and subtracted from
Jupiter's spectrum to search for non-hydrogenic emissions such as CO
and S. Upper limits are placed on several species of interest and the
results are used to interpret impact phenomena.
\np
\bc
{\bf Multiwavelength Observations of S--L 9 Impact Spots on Jupiter}\\[6pt]
\bi
R. Vasundhara$^1$ \& Pavan Chakraborty$^2$\\
Indian Institute of Astrophysics\\
Bangalore 560034\\[6pt]
\ei
\ec
$^1$e--mail: rvas@iiap.ernet.in\\
$^2$e--mail: pavan@iiap.ernet.in\\[6pt]
Observations of Jupiter made at the cassegrain (f/13) focus of the 102 cm
telescope at the Vainu Bappu Observatory during 18 -- 22 July 1994 and
13 -- 14 Aug. 1994 are reported. The images taken in July, were recorded
through six narrow band filters centered at 4862$\AA$, 4935$\AA$, 5083$\AA$,
6581$\AA$, 8900$\AA$ and 8930$\AA$ with FWHM ranging between 50 to 300 $\AA$.
The differential wave length dependence of the scattered light from the
impact regions compared to nearby satellites and the surrounding regions on
Jupiter are presented. Subsequent, images obtained during 13 --14 Aug, 1994
at 4862$\AA$ and 8930$\AA$ are compared with the July images to look for
changes in the wavelength dependence and size of the spots.
\np
\bc
{\bf Comet Shoemaker-Levy 9: A New Class of Object}\\[6pt]
\bi
Siacho Wang (PMO)\\[6pt]
\ei
\ec
The Comet SL9 has high abundance of sulfur and low abundance of H2O, CO
and nitrogen, but most of the fragments were embedded in circularly
summetric inner comae from July 1993 until late June 1994, implying
that there was continuous and weak outgassing activity. This indicates
that comet SL9 is a new class of object which is different from known
comets and asteroids. The main features of SL9 are 1) low abundance of
H2O, CO and nitrogen; 2) high abundance of sulfur; 3) existence of
central coherent body, not swarm of debris; 4) fragile nature; 5( low
albedo; 6) containing carbonaceous and silicate material; 7) low
volatile object. The existence of this new class object of SL9
indicated the variety of the objects in the solar system.
This work was mainly supported by Chinese Academy of Sciences, Chinese
National Science Foundation and Chinese Pacific Insurance Co. Ltd.
\newpage
\bc
{\bf Observations and Studies of Chinese Jupiter Watch}\\[6pt]
\bi
Sichao Wang (PMO), Bochen Qian (BAO) and Keliang Huang (NUU)\\
China\\[6pt]
\ei
\ec
Optical observations: 14 telescopes at 8 observatories or stations
joined the CJW. Using the CCD camera and CCD video camera,
observations of dark spots have been made at SAO, YAO, PMO, BAO and
some stations during the period between June 15 and Sept. 15, 1994. 6
Satellite flash observations have been succeeded at SAO (China) and 9
light curves of Galilean satellites have been obtained.
Radio observations: 5 radio telescopes at 5 observatory or stations
joined the CJW. During the impact periods, a steady flux density
increase of Jupiter was seen at 12cm and 13cm wavelength at BAS and UAS
respectively. Possible decametric radio bursts have been detected by
BAS. Impact predictions: J. X. Zhang and his colleagues provided the
July 7 edition of their heliocentric orbital elements and their impact
prediction of SL9.
This work was mainly supported by Chinese Academy of Sciences and
Chinese National Science Foundation.
\np
\bc
{\bf THERMAL EFFECTS FROM MINOR CONSTITUENTS\\
IN JUPITER'S UPPER ATMOSPHERE AFTER SL9}\\[6pt]
\bi
Y.~Wang \& K. S. Noll\\
Space Telescope Science Institute\\
3700 San Martin Dr.\\
Baltimore, MD 21218\\[6pt]
R. V. Yelle\\
NASA/Ames Research Center\\
MS245-3\\
Moffett Field, CA 94035-1000\\[6pt]
\ei
\ec
The thermal structure of Jupiter's atmosphere at pressures
between 10$^{-6}$ mbar and 100 mbar is calculated for both
pre-impact and post-impact conditions, using a radiative-conductive model.
For the pre-impact model, we include solar UV and EUV heating,
non-LTE cooling by hydrocarbon fundamental bands, cooling by \htwo\
collision-induced opacities, and heating by \chfour\ near-IR and
visible bands. The calculated temperature profile indicates that
extended heat sources other than known gas opacities have to be present
in order to explain the observed temperatures in both the stratosphere
and the mesosphere of Jupiter. We added a total heat flux of
175 ergs/\cmt /sec in the stratosphere, 15 ergs/\cmt /sec
in the mesosphere, assuming a Chapman profile for each source.
This heating is presumably related to the absorption of solar
energy by suspended aerosals.
Some reports find post-impact temperatures in the stratosphere
decreased by as much as several tens of degrees.
To study the effects of impact-generated gas on Jupiter's thermal
profile we consider a range of models with stratosphere abundances of
HCN, NH$_{3}$, and CO taken from published reports.
Our studies show that the cooling effects from the minor constituents including
HCN, CO, and NH$_{3}$, produced by the impact, are insignificant.
The existing thermal balance is dominanted by the main hydrocarbon
fundamental bands and \htwo\ collision-induced opacity, and
can not be perturbed significantly by the observed quantities of
impact-generated gases.
\np
\bc
{\bf Geometrical Model for the Plume Evolution}\\[6pt]
\bi
J. Watanabe, S. Takeuchi, H. Hasegawa, B. Suzuki and K. Sekiguchi\\[6pt]
\ei
\ec
A geometrical model of the evolution of the impact plume is
described. Although impact plumes were basically observed with the HST,
three-dimensional structure of the plumes is not clear. Considering
the geometrical distribution of the dust grains on the stratosphere at
the impact sites, we constract the three-dimensional model of the
plumes. By using this model, we discuss the nature of the light curve
of the impacts recorded by many grand-based observations with Near-IR
wavelength.
\np
\begin{center}
{\bf Temporal and Spatial Variations Among the Fragments of\\
Comet D/Shoemaker-Levy 9}\\[6pt]
\begin{it}
H. A. Weaver (STScI), M. F. A'Hearn (UMD), C. Arpigny (Li\`ege),\\
P. D. Feldman (JHU), Ph. Lamy (LAS), K. J. Meech (Hawaii),\\
K. S. Noll (STScI), \& T. E. Smith (STScI)\\[6pt]
\end{it}
\end{center}
Observations of comet \mbox{D/Shoemaker-Levy 9} (SL9) with the
Hubble Space Telescope began in July 1993 and continued systematically
throughout 1994. While a typical spatial brightness profile can be defined
for the SL9 fragments, there were also significant deviations from the
average behavior. For at least some cases, the deviations are likely
due to fragmentation events subsequent to the breakup of the SL9 parent
body. There are apparently secular trends in the core brightnesses of
some fragments, but generally the variation is less than 50\%. All
of the observed fragments showed a strong stretching of the coma near
the time of impact as the differential acceleration across the coma
due to Jupiter became significant.
\newpage
\bc
{\bf Comet Shoemaker-Levy 9: Support for the Rubble Pile Model}\\[6pt]
\bi
Paul R. Weissman\\
Jet Propulsion Laboratory\\
Pasadena, CA 91109\\[6pt]
\ei
\ec
The observed behavior of comet Shoemaker-Levy~9 as it orbited and impacted
Jupiter was consistent with predictions of the primordial rubble pile
(Weissman, 1986) and fractal (Donn et al., 1985) models for cometary nuclei.
The comet displayed repeated disruption events along its orbit as sub-nuclei
continued to separate from the individual fragments, and complete fading and
dispersal of some smaller fragments. Using the rubble pile model, Asphaug and
Benz (1994) demonstrated the reassembly of the disrupted comet into $\sim$15-20
fragments, with physically reasonable densities of 0.5 to 1.3 g cm$^{-3}$.
Impacting fragments deposited a substantial fraction of their energy in
Jupiter's upper atmosphere, consistent with a partially dispersed rubble pile.
\np
\begin{center}
{\bf Narrow-Band Imaging of the Impact Sites on Jupiter}\\[6pt]
\begin{it}
Dennis D. Wellnitz and Michael F. A'Hearn\\
University of Maryland\\
College Park, Maryland\\[6pt]
Ralph Martin and Arie Verveer\\
Perth Observatory\\
Western Australia\\[6pt]
\end{it}
\end{center}
During the month of July 1994, the University of Maryland/Perth Observatory
team recorded about 6000 images and spectra of Jupiter, observing from the
Perth Observatory in Western Australia. Jupiter was observable from about
1030 through 1630 UT each evening, and we enjoyed an unusually good run of
clear weather and near-arc-second seeing during much of impact week. Some
of the images were taken through narrow-band filters in methane absorption
bands, while others were taken in continuum or wide red filters; the total
wavelength range sampled was from about 500 to 900 nm. This data set permits
us to look at the reflectivity and absorptivity of the impact spots as a
function of height in the atmosphere of Jupiter, and to follow the evolution
of individual spots during July 1994. We may also integrate the absorption
of a spot over its extent and thereby obtain an estimate of the total mass
of the particles comprising the spot. The current status and results of
this analysis effort will be presented at the meeting as a poster paper.
\newpage
\begin{center}
{\bf Scattering Properties of Dust Associated with SL9-Jupiter Impact}\\[6pt]
\begin{it}
N.C.Wickramasinghe\\
University of Wales, Cardiff, U.K.\\[6pt]
K.S.Krishna Swamy\\
Tata Institute of Fundamental Research\\
Bombay, India\\[6pt]
\end{it}
\end{center}
The collision of SL9 with Jupiter injected substantial quantities
of cometary dust into the Jovian atmosphere at several impact sites,
inparticular at the G-site. Therefore the observation of radiation fluxes
from the impact site as a function of the time could yield important
information on the nature of the dust.
In our preliminary investigation, we have calculated the changes
in planetary albedos based on optically thin radiation transfer model of
an atmospheric haze with optical depth at 5500A and with the size
distribution function n(a)=const. a(-3.6). The laboratory measured n and k
values for the organic material has been used. The results indicate
significant drop in albedo in the UV, but the situation is dependent on
the dust loading, the grain parameters and on the composition. We hope
to explore wide range of models including multiple scattering.
\np
\bc
{\bf Chemistry of the Shoemaker-Levy 9 Jovian Impact Blemishes:\\
Indigenous Cometary vs. Shock-Synthesized Organic Matter}\\[6pt]
\bi
Peter D. Wilson and Carl Sagan\\
Laboratory for Planetary Studies\\
Cornell University\\
Ithaca, NY 14853\\[6pt]
\ei
\ec
We find that the optical constants of the aerosols in the dark impact
blemishes, as measured by West et al. (1995), are a near-identical match to
Murchison organic residue. This organic matter could be either (1)
indigenous to the impacting comet, or (2) shock-synthesized from the Jovian
atmosphere. A 1-km comet will produce an earth-sized blemish with $\tau=1$ if
5-15\% of its volume is deposited into the atmosphere as particles with
radii r=0.1-1.0 microns. Based on our most analogous charged-particle
irradiation experiments, the energy deposited into the Jovian atmosphere by
the same-sized impact is able to produce only enough organic matter to
reach $\tau=0.25$. This estimate, however, could easily be in error by an
order of magnitude, so we cannot conclusively exclude the shock-synthesis
mechanism. Given the high degree of similarity between the aerosols and
the organic residue extracted from the Murchison meteorite, though, we
conclude that the organic matter in the blemishes is most likely debris
from the impactors.
\np
\vspace*{-1cm}
\centerline{\bf Observations of the Jovian Satellites During Comet
P/Shoemaker-Levy 9's}
\centerline{\bf Impact with Jupiter }
\vskip .1in
\centerline{L. M. Woodney, R. Meier, M.F. A'Hearn, and D. Wellnitz}
\centerline{University of Maryland}
%\centerline{and}
\medskip
\centerline{T. Smith, A. Verveer, and R. Martin}
\centerline{Perth Observatory}
\vskip .1in
Once it was known that the impacts of the fragments of comet
P/Shoemaker-Levy 9 would occur behind the limb of Jupiter it was
expected that reflections off of satellites would be one of the best
ways to view the entry flashes from Earth. However, the results of the
attempts to observe this effect were disappointing. To date, no one
has reported a significant detection of a flash, but there are several
reports of possible flashes. Each of these detections require
confirmation from other observers to establish whether or not they are
noise.
Our own data contain two of these possible flashes. We observed Io, Europa
and/or the limb of Jupiter during the expected impact times of fragments D, E,
and K from two sites in Western Australia. At the Perth Observatory 61 cm
telescope we used a CCD camera and broad band filters, while at Mt. Singleton
we used an unfiltered, high-speed, blue sensitive photometer and a 14 inch
Celestron. Our best photometer observations are from the time of the D impact.
These data also include our best possibility for an observed flash. There is
a 7\% increase in the brightness of Io which lasts several seconds. There is
a second possible flash at the time of impact of E, which is seen in both
the photometer data and a CCD image, but both detections could easily be
explained by noise. To establish whether or not these events are real, high
signal to noise data from other observers is needed.
The luminosities that we derive from both possible flashes are two
orders of magnitude greater than seen by Galileo for other events.
This implies that the spectra of these flashes were either very
different from those of black-bodies, or possibly that they were like
those of very hot black-bodies.
Our upper limit for the luminosity of
impact K of \mbox{6 $\times 10^{23}$ erg sec$^{-1} \mu m^{-1}$}
at 945 nm is only a few times brighter than the peak observed by Galileo.
Perhaps better data reduction will reveal a flash.
\np
\begin{center}
{\bf Physical Properties of Swarmed SL9 Fragments at Impact}\\
\vspace{0.3in}
Xingfa Xie and
Michael J. Mumma\\
NASA/GSFC
\vspace{0.1in}
Kevin M. Olson\\
George Mason University\\
\end{center}
We present results from an N-body simulation of the swarms made of
tens-meter-sized objects, beginning at apojove and ending seconds
before impact. Our simulation shows the swarm to be stretched
into a long train along the direction of orbital motion, with a high
mass concentration at the center. The initial sizes of the swarms
at apojove are estimated to be in the range of 20-50 km for swarm
masses of $10^{13}-10^{15}$ g, based on the light
curves obtained by Galileo. Incorporation of particle collisions into
our model is currently in progress.
\np
\bc
{\bf Explanation of Flashes and Bright Flare in IR-Lightcurves of Shoemaker-Levy
9 Impacts: Comparison between Numerical Simulations and Observations}\\[6pt]
\bi
Takashi Yabe, Masakazu Tajima, Sho Sasaki, Yutaka Abe, Feng Xiao,\\
Takayuki Aoki, and Jun-ichi Watanabe\\[6pt]
\ei
\ec
The strong IR emission and the preceding flashes at Comet Shoemaker-Levy~9
impacts into Jupiter are studied based on the numerical simulation of the
explosion process. 2-D and 3-D simulations of impact and explosion
processes are performed using highly accurate hydrocode ExCIPHER. Energy
deposition at the shallower depth along an elongated trajectory of cometary
entry can generate the first rapid rising fireball as well as a subsequent
broad plume. Calculated time intervals are compatible with the secondary
flash and the strong bright flare in IR-lightcurves. Obtained temperature
evolution can explain the observed rapid decay of the strong flare.
\np
\bc
{\bf CCD Methane Band Modelling of A, H, L and R Impacts}\\[6pt]
\bi
Padma A. Yanamandra-Fisher, Jose Luis Ortiz and Glenn S. Orton\\
Jet Propulsion Laboratory, Pasadena, CA 91109\\[6pt]
\ei
\ec
Time series of impacts (H, L, R) at 0.89 $\mu$m and (A, H, L)
\mbox{0.945 $\mu$m} indicate that the main event or the major brightening
of the plume occurred and is in phase with the peak of the event as observed
at 2.3 $\mu$m. However, the first and second pre-cursors are not always
evident in the CCD methane band data. We are presently working on
modelling these events to establish the spectral energy distribution of
the fragments. Our data set comprises of data from Calar Alto, La
Palma and Table Mountain observatories.
\np
\bc
{\bf Three strong Jovian decametric radio bursts from impacts}\\[6pt]
\bi
Xi-Zhen Zhang$^{1}$, Jin-Lin Han, \& Qi-Bin Li\\
Beijing Astronomical Observatory\\
Chinese Academy of Sciences\\
Beijing 100080, P.R. China\\[6pt]
\ei
\ec
\bi
$^{1}$email: zxz@bao01.bao.ac.cn\\[6pt]
\ei
Three strong decametric radio bursts ($>$20db), undoubtedly
related to the impacts of fragments G, K, and W of Comet
Shoemaker-Levy 1993e (SL-9) on Jupiter, have been detected
during the impact week at Xin-Xiang temporary Jovian Decametric
Watch Station of Beijing Astronomical Observatory. All of them
are narrow band events occurred at about 26.0 and 28.5MHz, and
have a long duration of at least several minutes. Their
completely different characteristics, (ie. strongest one before G
impact, immediate response to K impact, and switching bursts
after W impact), are shown in this report.
The project is supported by the National Natural Science
Foundation of China.
\np
\bc
{\bf On Jovian Decametric Radio Bursts of the Great Comet Crash}\\[6pt]
\bi
Xi-Zhen Zhang , Lin-Lin Han, Qi-Bin Li , Pei-Nan Jiao, Jun-Hu Du\\[6pt]
\ei
\ec
Strong decametric narrow-band radio bursts (N events) and broad-band
storms, produced by impacts of fragments of Comet Shoemaker-Levy 1993e
(SL-9) on the Jupiter, have been detected during our observations from
July 17 to 22, 1994 at the Xin-Xiang temporary Jovian Decametric
Station (longitude = -113.8 degrees, latitude = 35.3 degrees) of the
Beijing Astronomical Observatory. Observations were carried out in the
scanning mode in the frequency range from 24.0 OMHz to 28.5 MHz.
Signals were detected from 10 narrow bands in a step of 0.5 MHz, and
each band has a bandwidth of 0.1MHz and a sampling time of 0.1 second.
Plots of relative signal intensity of these bursts at 10 frequencies
between 24.0 and 28.5 MHz has been published (Zhang et al., 1994 and
Han et al., 1994). In this paper we report some preliminary analysis
results on three strong radio bursts, which were apparently produced by
G, K and W fragment impacts on July 18, 19 and 22, respectively. Also
some spectrum analysis are presented on decameter storms which appears
to be related to the impact of fragment S$=$5 on July 21.
\np
\bc
{\bf THE PREDICTION OF THE IMPACT OF COMET SHOEMAKER-LEVY 9 ON JUPITER}\\[6pt]
\bi
J.-X. Zhang, Q. Wang, J.X. Yang, S.C. Wang, X.Z. Chen\\
Purple Mountain Observatory, Nanjing, China\\[6pt]
\ei
\ec
Using numerically self-established dynamical model for solar system objects,
exploring method and making software, we successfully sent out several times
of prediction from April to July 1994, and the predictions mainly coincided
with actuality. The method and theory of the predictions are expounded
briefly in this paper, and the precicted impact items are compared and analyzed with actual accented impact times newly confirmed. The nuclei's movement
when they were in the vicinity of Jupiter and the impact positions are also
discussed.
\np
\bc
{\bf THE LIGHT CURVES OF GALILEAN SATTELITES DURING THE COLLISIONS OF
COMET SHOEMAKER-LEVY 9 AND JUPITER}\\[6pt]
\bi
Hongnan Zhou\\
Dept. of Astronomy\\
Nanjing University\\
Nanjing 210093\\
P. R. China\\[6pt]
\ei
\ec
In this paper, we present the light curves of Galilean
Sattelites during the fragments D=19, E=18, K=12, N=9, P2=8b and
S=5 impact with Jupiter.
\np
\bc
{\bf THE IMPACT TIME OF FRAGMENT P2=8b}\\[6pt]
\bi
Hongnan Zhou\\
Dept. of Astronomy\\
Nanjing University\\
Nanjing 210093\\
P. R. China\\[6pt]
\ei
\ec
According to the light curve of Io during the fragment
p2=8b impacts with Jupiter, we obtained the precise impact time
of fragment p2=8b.
\end{document}
