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Session 42 - Solar Systems.
Display session, Tuesday, January 16
North Banquet Hall, Convention Center

[42.17] Ion-Induced Chemistry on Icy Satellite Surfaces: Evidence from Hubble Space Telescope Ultraviolet Spectra

K. S. Noll (STScI), R. Johnson (U.VA), A. L. Lane (JPL), D. Cruikshank, Y. Pendleton (NASA-Ames), T. Roush (SFSU), D. Domingue (LPI), H. Weaver (ARC)

The dominant surface components of satellites in the outer solar system are water ice and dark, presumably silicaceous material in variable mixtures. These satellites surfaces are exposed to high energy ions in the magnetospheres of their primary planet. With UV spectra obtained by the Hubble Space Telescope we have detected at least two molecular absorption bands produced by the products of ion irradiation, SO_2 on Europa and O_3 on Ganymede. We compare the spectra of these two satellites to UV spectra of other ice-rich satellites Iapetus and Rhea, and to the ice-poor asteroid, Ceres. Ozone, in particular, appears to be diagnostic of ion-irradiation of ice. It is produced either directly, or indirectly by ultraviolet photlysis of O_2. Because the key ingredients are ubiquitous, we expect that objects with tenuous O_2 atmospheres, and associated O_3 will be common in extrasolar planetary systems.

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