HR: 08:15h
AN: P51E-02    [Abstracts]
TI: Europa's surface composition: What we know, what we would like to know, and how we can find out
AU: * Carlson, R W
EM: Robert.W.Carlson@jpl.nasa.gov
AF: Jet Propulsion Laboatory, California Institute of Technology, Pasadena, CA 91109, United States
AU: Calvin, W
EM: wcalvin@unr.edu
AF: Univ. of Nevada, Dept. of Geology, Reno, NV 80134,
AU: Dalton, J B
EM: dalton@mail.arc.nasa.gov
AF: SETI Institute, Carl Sagan Center, Moffett Field, CA 94043,
AU: Hansen, G B
EM: ghansen@rad.ess.washington.edu
AF: Univ. of Washington, Earth and Space Science, Seattle, WA 98195,
AU: Hudson, R
EM: hudsonrl@eckerd.edu
AF: Eckerd College, Dept. of Chemistry, St. Petersburg, FL 33733,
AU: Johnson, R E
EM: rej@virginia.edu
AF: Univ. of Virginia, Enginering Physics, Charlotteseville, VA 22904,
AU: McCord, T B
EM: mccordtb@aol.com
AF: Bear Fight Center, 22 Fiddler's Road, Winthrop, WA 9882,
AU: Moore, M H
EM: Marla.H.Moore@nasa.gov
AF: NASA Goddard Space Flight Center, Cosmic Ice Laboratory, Greenbelt, MD 20771,
AB: Europa's icy surface contains both exogenic and endogenic material, and these materials can be modified by radiation and impact-generated processes. Determining the parent molecules and their possible origins is important for studying surface-subsurface exchange and the chemical content of Europa's putative ocean. The surface is known to contain water ice in both amorphous and crystalline form, as well as water in hydrated compounds. The identity of the hydrated molecules is not established; salts, acids, or combinations of both have been suggested. The presence of salts would indicate an endogenic source, acids can arise from both internal and external sources. Sodium and potassium atoms are observed escaping from Europa's surface, possibly originating from endogenic salts or exogenic plasma and neutral atom torii. Europa's brownish chromophore is often suggested to be sulfur, which known to be implanted in the surface by Iogenic plasma but may also be a product of salt or acid radiolysis. Molecular oxygen and hydrogen peroxide are present and are clearly radiolysis products. Sulfur dioxide and carbon dioxide can arise from exogenic or endogenic sources and may be components of radiolytic sulfur and carbon cycles. Volatile molecules such as CO₂ and O₂ may be trapped within defects or clathrate structures. Further studies with higher sensitivity and specificity can elucidate the relative roles of exogenic and endogenic sources and allow searches for minor species, including organic molecules and potential biomarkers. Such studies can be performed using ultraviolet, visible, and near- and mid- infrared remote sensing. Observations of Europa's sputter atmosphere can be used to infer the surface composition while grains, ejected from the surface and forming Europa's dust cloud, are also potential compositional indicators.
DE: 5410 Composition (1060, 3672)
DE: 5421 Interactions with particles and fields
DE: 5422 Ices
DE: 5464 Remote sensing
DE: 6221 Europa
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting