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The spatial morphology of Europa's near-surface O2 atmosphere |
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| Authors: | T.A. Cassidy R.E. Johnson M.C. Wong |
| Affiliation: | a Engineering Physics Program and Astronomy Department, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325, USA b NASA Marshall Spaceflight Center, VP01, Huntsville, AL 35812, USA c Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, USA d Heliospheric Physics Laboratory, Code 672, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA |
| Abstract: | Results from a three-dimensional ballistic model of Europa's O2 atmosphere are presented. Hubble Space Telescope (HST) ultraviolet observations show spatially non-uniform O2 airglow from Europa. One explanation for this is that the O2 atmosphere is spatially non-uniform. We show that non-uniform ejection of O2 alone cannot reproduce the required morphology, but that a non-uniform distribution of reactive species in Europa's porous regolith can result in a non-uniform O2 atmosphere. By allowing O2 molecules to react with Europa's visibly dark surface material, we produced a spatially non-uniform atmosphere which, assuming uniform electron excitation of O2 over the trailing hemisphere, compares favorably with the morphology suggested by the HST observations. This model, which requires a larger source of O2 than has previously been estimated, can in principal be tested by the New Horizons observations of Europa's O2 atmosphere. |
| Keywords: | Europa Regoliths Satellites, atmospheres Satellites, surfaces |
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