Radiolysis and Trapping of O2 and O3 in Water Ice

TEOLIS, B. D.; VIDAL, R. A.,; LOEFFLER, M. J.; BARAGIOLA, R. A.

Cambridge, Inglaterra

Workshop; 37th DPS (Division for Planetary Science) Meeting; 2005

American Astronomical Society

We are interested in the question of how oxygen exospheres are produced around icy objects in the outer solar system. To characterize the production, trapping and escape of O2 caused by magnetospheric particle bombardment of icy surfaces, we irradiated water ice films with 100 keV ions and studied the O2 emission at different temperatures and radiation fluences. Our results show the production of a highly concentrated sub-surface layer of trapped O2 when irradiation is performed at 130 K or above, which is attributed to hydrogen escape from the near surface region. Thermal and radiation induced diffusion are also demonstrated, and these phenomena are seen to influence the fluence dependence of the O2 emission. Recent experiments indicate that high concentrations of radiolyzed O2 are produced and retained in ices at sufficiently high temperatures, such as those found in the equatorial regions of the icy galilean satellites. We will also discuss the possibility of ozone production from ices with high O2 concentrations. Work supported by NSF-Astronomy and NASA's Cassini and Planetary Atmospheres Program.