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R.E. Johnson (University of Virginia), P.D. Cooper, T.I. Quickenden (University of Western Australia)
The oxidants produced by radiolysis and photolysis in the icy surface of Europa may be necessary to sustain carbon-based biochemistry in Europa’s putative subsurface ocean. Because the subduction of oxidants to the ocean presents considerable thermodynamic challenges, we examine the formation of oxygen and related species in Europa’s surface ice with the goal of characterizing the chemical state of the irradiated material. Relevant spectral observations of Europa and the laboratory data on the production of oxygen and related species are first summarized. Since the laboratory data is incomplete, we examine the rate equations for formation of oxygen and its chemical precursors by radiolysis and photolysis (Johnson et al. 2003). Measurements and simple rate equations are suggested that can be used to characterize the production of oxidants in Europa’s surface material and the chemical environment produced by radiolysis. Possible precursor molecules and the role of radical trapping are examined. We note that the trapped O2 associated with these spectral features can also be produced via radiation-induced decomposition of hydrogen peroxide dimers contained in hydrogen peroxide inclusions in Europa's surface (Cooper et al 2003). The possibility of oxygen reactions on grain surfaces in Europa’s regolith is discussed and the earlier estimate of the supply of O2 to the atmosphere are increased. Cooper, P.D. et al. Icarus sumitted (2003) Johnson, R.E. et al. Astrobiology J in press (2003)
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.