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M.J. Loeffler, U. Raut, R.A. Vidal, R.A. Baragiola (University of Virginia, Laboratory for Atomic and Surface Physics, Charlottesville, VA 22904, USA), R.W. Carlson (Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, 91109)
There has been a recent interest in the possible production mechanisms of H2O2 in water ice, since the Galileo NIMS instrument reported an absorption band (3.5 µm) on the surface of Europa (Carlson 1999). Here we present results from laboratory studies that show H2O2 creation and destruction by ion bombardment. We have found that 100 keV H+ irradiation can produce H2O2 from a water ice film at temperatures as high as 120 K and have measured the production rates at 20 K and 80 K. Furthermore, we have studied the temperature dependence and stability of the 3.5 µm band. To understand the nature of the peroxide produced by ion irradiation, we have grown solid hydrogen peroxide by distillation in an ultra high vacuum chamber and have used infrared spectroscopy to study the band shape and position as a function of temperature in various mixtures of water. Furthermore, we have measured the crystallization and sublimation of H2O2 at temperatures between 155 and 190 K. We have also irradiated a film of crystalline H2O2 with 20 keV H+ at 80 K and have observed what is most likely amorphization of the peroxide. Furthermore, infrared spectroscopy indicated that during irradiation, water and ozone are produced, while HO2 is not detected. The presence of ozone suggests that H2O2 is a likely precursor molecule for oxygen formation at 80 K.
Work supported by NSF Astronomy, NASA Planetary Atmospheres and Origin programs.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.