10639(  1) - 04/05/05 12:11  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      10639
                                                       Version: 1
                                                       Check-in Date: 05-Apr-2005
                                                                      16:11:17

1.Proposal Title:
Studies of Europa's Plasma Interactions and Atmosphere with HST/STIS FUV Images
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2. Proposal For  3. Cycle  4. Parallel Pointing Tolerance
AR               14        <none>
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5. Investigators
                                                                                     Contact?
    PI: Dr. Gilda E. Ballester            University of Arizona
   CoI: Prof. Margaret Kivelson           University of California - Los Angeles        N
   CoI: Dr. Floyd L. Herbert              University of Arizona                         N
   CoI: Dr. Krishan K. Khurana            University of California - Los Angeles        N
   CoI: Dr. Michael R. Combi              University of Michigan                        N

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6. Abstract

Europa's tenuous atmosphere was discovered by HST/GHRS in OI 1304 A and OI] 1356 A
emissions that were inferred to be produced by Jovian plasma electrons
dissociatively exciting molecular oxygen (the dominant end product of a water-
derived atmosphere). The properties and spatial distribution of Europa's FUV
emissions are diagnostic for the specific characteristics of Europa's magnetospheric
interactions and atmosphere. Although Europa's plasma interaction was expected to
resemble Io's, later HST/STIS FUV imaging studies have yielded unexpected, puzzling
results. Therefore, many fundamental questions regarding the nature of Europa's
thin, water-derived atmosphere, and of its plasma interactions, induced magnetic
field, and emission excitation processes still remain. The proposed Archival program
will address these questions by analyzing the existing set of STIS FUV images of
Europa concentrating on the temporal variations that have not been reported in the
literature. The derived distribution of the emissions and variations with magnetic
System III longitude and plasma conditions will be compared with expectations based
on the various published models of the Europa's magnetospheric interaction.
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                                                10639(  1) - 04/05/05 12:11  - [  2]

            Summary Form for Proposal  10639

  Item                         Used in this proposal
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  Proposal Category            AR
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