9113( 5) - 02/16/01 12:50 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9113 Version: 5 Check-in Date: 16-Feb-2001 12:48:56 1.Proposal Title: Solar UV Radiation and the Origin of Life on Earth ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 10 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Sara Heap NASA Goddard Space Flight Center CoI: Dr. Eric Gaidos CalTech N CoI: Dr. Ivan Hubeny Goddard Space Flight Center N CoI: Prof. James F. Kasting Pennsylvania State University N CoI: Dr. Thierry Lanz Goddard Space Flight Center N ------------------------------------------------------------------------------------ 5. Abstract Prior to 3.5 Gyr ago when life arose on Earth, the ultraviolet emission of the early Sun was more intense than at present. This radiation helped shape the chemical environment of the early Earth and hence influenced prebiotic evolution, the origin of life, and its subsequent early development. We propose to investigate this UV emission by making an efficient, systematic study of the UV spectra of 8 stars believed to resemble the early Sun. beginitemize em We will use the observed UV flux distributions as boundary conditions in photochemical models of the Earth's atmosphere, in order to estimate the concentrations of greenhouse gases and other molecules that may have played a major role in the origin of life. em We will also use the spectra to construct semi- empirical models of the chromospheres of these young solar analogs. The chromospheric models will enable us to predict the extreme- UV emission of the early Sun and its consequences for the erosion of the early Earth's atmosphere and the altered oxidation state of the planet. em We will investigate the effect of metallicity on the UV emission and its consequences for the photochemistry of Earth-like planets. enditemize ------------------------------------------------------------------------------------ 9113( 5) - 02/16/01 12:50 - [ 2] Observations Description ------------------------ Requirements We will observe with STIS in the E*M modes because of BOP limitations (LyAlpha emission, strong NUV flux). The program stars have similar fluxes, so we will observe each for the same amount of time (2 orbits). The STIS spectra of each program star should be adequate: o to derive the UV flux distribution (E140M, E230M) at a resolution sufficient to identify, chromospheric emission lines and measure their strengths; o to check the fundamental parameters of the star (E140M, E230M); o to detect the presence of comet-like objects transiting the star (E230M). subsectionEstimation of Count- Rates To estimate exposure times for the E140M spectra, we scaled from our STIS/E140M spectrum of the V=6.4 star, HD 43162, obtained in program 8787. The exposure time for that observation was 38.7 minutes. The resultant far-UV spectrum shown in Figure 1 was binned in 0.25-Angstrom bins and further smoothed by a 15- point running average. While this data-manipulation served to produce a spectrum comparable to the UARS spectrum of the Sun and is adequate for analysis, we plan to double the exposure time so as to compensate for the somewhat lower fluxes of the program stars (cf. the textitObserving Summary for the V magnitudes of the program stars.) To estimate exposure times for the E230M spectra, we used Kurucz' (1992) model SED's for the appropriate T_ eff, log g, and metallicity of the star and scaled according to the V magnitude of the star. The UV flux distribution of HD 43162 is shown in the top panel of Figure 3. (The far-UV portion is observed; the near-UV section is from a Kurucz SED). We then calculated count-rates using the STIS IDT program, SIM\_STIS. This program incorporates the measured post-launch sensitivities of the instrument in each mode. beginfigureh centerline psfigfigure=/home/heap/gstar/cycle10/simulations.eps, height=6 .cm endfigure textitUV Flux Distribution. Photochemical models (\S 3.2) require as input only a coarse UV flux distribution, e.g. fluxes in 25-Angstrom\ bins. We will observe with the 0.2X0.2 arcsec slit in order to get a good measure of the absolute flux distribution. Note that in Figure 3 the observed flux at Lambda ~ 1700 Angstrom\ is several times higher than given by the Kurucz SED. This discrepancy may be caused by errors in far-UV opacities and/or by the omission of any chromospheric continuum flux. The discrepancy emphasizes the need for reliable observations. textitDiagnostic Features in the Mid-UV Spectrum. We have developed UV spectral diagnostics of temperature and metallicity of cool stars (Lanz et al. 1999) based on STIS E230M spectra of F-type stars obtained in program 7433 (Heap et al. 1998). The major photospheric features are: the MgI Lambda2852 resonance line, the MgII Lambda2800 resonance doublet, and the spectral break at 2640 Angstrom . All three diagnostics can be observed in a single E230M exposure and will be useful in refining the atmospheric parameters of each program star. An E230M spectrum should also work well for detecting the absorption of comet-like objects, if present. Again, a high resolution is needed to detect these sharp absorptions. textitVariability. We will obtain the E140M exposures in the time-tagged mode in order to follow a flare should one occur during the observation. subsectionEstimate of Orbits We have devised an efficient program in which only two orbits are needed per program star. We assume that an average orbit is 56 minutes long. In a given visit to a program star, the following exposure sequence is taken: target acquition, G430M (10 sec; CaII K emission); E230M (20 minutes; near-UV spectrum 2300- 3140Angstrom ); E140M (80 minutes; 1160-1720 Angstrom ). The G430M exposure to observe the chromospheric emission in the CaII K line occurs right after target acquisition and placement in the 0.2x0.2" slit. This observation will be useful, and the exposure time is negligible. Real Time Justification ----------------------- We have acquired ground-based spectra of the targets in order to determine the fundamental parameters of each of the program stars (Gaidos et al. 2000, Gaidos & Gonzalez, in prep). Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9113( 5) - 02/16/01 12:50 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD116956 STAR, G V-IV RA=13H 25M 45.76S +/- 0.2", J2000 V = 11 V = 7.29+/-0.05 DEC=+56D 58' 13.7" +/- 0.2" B-V = 0.804 Coordinate Source: HIPPARCOS/TYCHO_CATALOGUE Comments: G9IV-V star, Coordinates are Epoch 1991.25 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 -0.02659 0.01121 0.04576 2 HD37394 STAR, G V-IV RA=05H 41M 20.33S +/- 0.2", J2000 V = 2.0 V = 6.21+/-0.05 DEC=53D 28' 56.4" +/- 0.2" B-V = 0.840 Coordinate Source: HIPPARCOS/TYCHO_CATALOGUE Comments: K1V star, Coordinates are Epoch 1991.25 For S/N=100, ETC gives 0.17 S Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 0.0003 -0.5236 0.08169 3 HD203244 STAR, G V-IV RA=21H 24M 40.42S +/- 0.2", DEC= J2000 V = 11 V = 6.98+/-0.05 -68D 13' 41.7" +/- 0.2" B-V = 0.723 Coordinate Source: HIPPARCOS/TYCHO_CATALOGUE Comments: G5V star, Coordinates are Epoch 1991.25 For S/N=100, ETC gives 0.35 S Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 0.0253 0.1694 0.04886 4 HD128987 STAR, G V-IV RA=14H 40M 31.17S +/- 0.2", DEC= J2000 V = -23 V = 7.24+/-0.05 -16D 12' 32.9" +/- 0.2" B-V = 0.710 Coordinate Source: HIPPARCOS/TYCHO_CATALOGUE Comments: G6V star, Coordinates are Epoch 1991.25 For S/N=100, ETC gives 0.45 S Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 -0.0078 -0.0652 0.04243 5 HD59967 STAR, G V-IV RA=07H 30M 42.58S +/- 0.2", DEC= J2000 V = 9 V = 6.66+/-0.05 -37D 20' 22.2" +/- 0.2" B-V = 0.641 Coordinate Source: HIPPARCOS/TYCHO_CATALOGUE Comments: G3V star, Coordinates are Epoch 1991.25 For S/N=100, ETC gives 0.26 S Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 -0.0074 0.0538 0.04593 6 HD73350 STAR, G V-IV RA=08H 37M 50.47S +/- 0.2", DEC= J2000 V = 35 V = 6.74+/-0.05 -06D 48' 25.2" +/- 0.2" B-V = 0.655 Coordinate Source: HIPPARCOS/TYCHO_CATALOGUE Comments: G0 star, Coordinates are Epoch 1991.25 For S/N=100, ETC gives 0.28 S Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 -0.0200 0.0433 0.04232 7 HD165185 STAR, G V-IV RA=18H 6M 23.64S +/- 0.2", DEC=- J2000 V = 15 V = 5.94+/-0.05 36D 1' 11.3" +/- 0.2" B-V = 0.615 Coordinate Source: HIPPARCOS/TYCHO_CATALOGUE Comments: G3V star, Coordinates are Epoch 1991.25 For S/N=100, ETC gives 0.13 S 9113( 5) - 02/16/01 12:50 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 0.0087 0.0080 0.05758 8 HD97334 STAR, G V-IV RA=11H 12M 32.53S +/- 0.2", J2000 V = -4 V = 6.41+/-0.05 DEC=35D 48' 52.0" +/- 0.2" B-V = 0.600 Coordinate Source: HIPPARCOS/TYCHO_CATALOGUE Comments: G0V star, Coordinates are Epoch 1991.25 For S/N=100, ETC gives 0.21 S Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 -0.0204 -0.1513 0.04604 9113( 5) - 02/16/01 12:50 - [ 5] Visit: 01 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 111 HD116956 STIS/C ACQ F28X50O MIRROR 1 0.7 S CD III ------------------------------------------------------------------------------------------------------------------------------------ 112 HD116956 STIS/N ACCUM 0.2X0.2 E230M 2707 WAVECAL=NO 1 20 M MAX DUR UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 113 WAVE STIS/N ACCUM 0.2X0.2 E230M 2707 1 DEF UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 114 HD116956 STIS/F ACCUM 0.2X0.2 E140M 1425 1 12 M END ORBIT UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 116 HD116956 STIS/F ACCUM 0.2X0.2 E140M 1425 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 117 WAVE STIS/F ACCUM 0.2X0.2 E140M 1425 1 DEF UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9113( 5) - 02/16/01 12:50 - [ 6] Visit: 02 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 211 HD37394 STIS/C ACQ F28X50O MIRROR 1 0.2 S CD III ------------------------------------------------------------------------------------------------------------------------------------ 212 HD37394 STIS/N ACCUM 0.2X0.2 E230M 2707 WAVECAL=NO 1 20 M MAX DUR UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 213 WAVE STIS/N ACCUM 0.2X0.2 E230M 2707 1 DEF UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 214 HD37394 STIS/F ACCUM 0.2X0.2 E140M 1425 1 12 M END ORBIT UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 216 HD37394 STIS/F ACCUM 0.2X0.2 E140M 1425 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 217 WAVE STIS/F ACCUM 0.2X0.2 E140M 1425 1 DEF UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9113( 5) - 02/16/01 12:50 - [ 7] Visit: 03 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 311 HD203244 STIS/C ACQ F28X50O MIRROR 1 0.4 S CD III ------------------------------------------------------------------------------------------------------------------------------------ 312 HD203244 STIS/N ACCUM 0.2X0.2 E230M 2707 WAVECAL=NO 1 20 M MAX DUR UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 313 WAVE STIS/N ACCUM 0.2X0.2 E230M 2707 1 DEF UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 314 HD203244 STIS/F ACCUM 0.2X0.2 E140M 1425 1 14 M END ORBIT UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 316 HD203244 STIS/F ACCUM 0.2X0.2 E140M 1425 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 317 WAVE STIS/F ACCUM 0.2X0.2 E140M 1425 1 DEF UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9113( 5) - 02/16/01 12:50 - [ 8] Visit: 04 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 411 HD128987 STIS/C ACQ F28X50O MIRROR 1 0.5 S CD III ------------------------------------------------------------------------------------------------------------------------------------ 412 HD128987 STIS/N ACCUM 0.2X0.2 E230M 2707 WAVECAL=NO 1 20 M MAX DUR UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 413 WAVE STIS/N ACCUM 0.2X0.2 E230M 2707 1 DEF UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 414 HD128987 STIS/F ACCUM 0.2X0.2 E140M 1425 1 12 M END ORBIT UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 416 HD128987 STIS/F ACCUM 0.2X0.2 E140M 1425 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 417 WAVE STIS/F ACCUM 0.2X0.2 E140M 1425 1 DEF UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9113( 5) - 02/16/01 12:50 - [ 9] Visit: 05 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 511 HD59967 STIS/C ACQ F28X50O MIRROR 1 0.3 S CD III ------------------------------------------------------------------------------------------------------------------------------------ 512 HD59967 STIS/N ACCUM 0.2X0.2 E230M 2707 WAVECAL=NO 1 20 M MAX DUR UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 513 WAVE STIS/N ACCUM 0.2X0.2 E230M 2707 1 DEF UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 514 HD59967 STIS/F ACCUM 0.2X0.2 E140M 1425 1 12 M END ORBIT UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 516 HD59967 STIS/F ACCUM 0.2X0.2 E140M 1425 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 517 WAVE STIS/F ACCUM 0.2X0.2 E140M 1425 1 DEF UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9113( 5) - 02/16/01 12:50 - [ 10] Visit: 06 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 611 HD73350 STIS/C ACQ F28X50O MIRROR 1 0.3 S CD III ------------------------------------------------------------------------------------------------------------------------------------ 612 HD73350 STIS/N ACCUM 0.2X0.2 E230M 2707 WAVECAL=NO 1 20 M MAX DUR UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 613 WAVE STIS/N ACCUM 0.2X0.2 E230M 2707 1 DEF UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 614 HD73350 STIS/F ACCUM 0.2X0.2 E140M 1425 1 12 M END ORBIT UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 616 HD73350 STIS/F ACCUM 0.2X0.2 E140M 1425 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 617 WAVE STIS/F ACCUM 0.2X0.2 E140M 1425 1 DEF UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9113( 5) - 02/16/01 12:50 - [ 11] Visit: 07 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 711 HD165185 STIS/C ACQ F28X50O MIRROR 1 0.2 S CD III ------------------------------------------------------------------------------------------------------------------------------------ 712 HD165185 STIS/N ACCUM 0.2X0.2 E230M 2707 WAVECAL=NO 1 20 M MAX DUR UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 713 WAVE STIS/N ACCUM 0.2X0.2 E230M 2707 1 DEF UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 714 HD165185 STIS/F ACCUM 0.2X0.2 E140M 1425 1 12 M END ORBIT UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 716 HD165185 STIS/F ACCUM 0.2X0.2 E140M 1425 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 717 WAVE STIS/F ACCUM 0.2X0.2 E140M 1425 1 DEF UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9113( 5) - 02/16/01 12:50 - [ 12] Visit: 08 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 811 HD97334 STIS/C ACQ F28X50O MIRROR 1 0.2 S CD III ------------------------------------------------------------------------------------------------------------------------------------ 812 HD97334 STIS/N ACCUM 0.2X0.2 E230M 2707 WAVECAL=NO 1 20 M MAX DUR UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 813 WAVE STIS/N ACCUM 0.2X0.2 E230M 2707 1 DEF UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 814 HD97334 STIS/F ACCUM 0.2X0.2 E140M 1425 1 12 M END ORBIT UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 816 HD97334 STIS/F ACCUM 0.2X0.2 E140M 1425 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 817 WAVE STIS/F ACCUM 0.2X0.2 E140M 1425 1 DEF UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9113( 5) - 02/16/01 12:50 - [ 13] Summary Form for Proposal 9113 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50OIII 0.2X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/NUV-MAMA STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters WAVECAL=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements MAX DUR END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR E230M E140M ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD116956 WAVE HD37394 HD203244 HD128987 HD59967 HD73350 HD165185 HD97334 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 2707 1425 ------------------------------------------------------------------------------------------------------------------------------------