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Hubble Space Telescope observations of Europa in and out of eclipse

Published online by Cambridge University Press:  24 August 2010

W.B. Sparks*
Affiliation:
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
M. McGrath
Affiliation:
NASA Marshall Space Flight Center, Huntsville, AL 35812, USA
K. Hand
Affiliation:
Jet Propulsion Laboratory, California Institute of Technology, MS 183-601, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
H.C. Ford
Affiliation:
Department of Physics & Astronomy, The Johns Hopkins University, Bloomberg Center, 3400 N. Charles Street, Baltimore, MD 21218, USA
P. Geissler
Affiliation:
Center for Astrogeology, U.S. Geological Survey, 2255 N. Gemini Drive, Flagstaff, AZ 86001, USA
J.H. Hough
Affiliation:
Centre for Astrophysics Research, Science & Technology Research Institute, University of Hertfordshire, College Lane, Hatfield, AL10 9AB, UK
E.L. Turner
Affiliation:
Department of Astrophysical Sciences, 122 Peyton Hall, Princeton University, Princeton, NJ 08544, USA The University of Tokyo, Japan
C.F. Chyba
Affiliation:
Department of Astrophysical Sciences, 122 Peyton Hall, Princeton University, Princeton, NJ 08544, USA
R. Carlson
Affiliation:
Jet Propulsion Laboratory, California Institute of Technology, MS 183-601, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
M. Turnbull
Affiliation:
Global Science Institute, P.O. Box 252, Antigo, WI 54409, USA

Abstract

Europa is a prime target for astrobiology and has been prioritized as the next target for a National Aeronautics and Space Administration flagship mission. It is important, therefore, that we advance our understanding of Europa, its ocean and physical environment as much as possible. Here, we describe observations of Europa obtained during its orbital eclipse by Jupiter using the Hubble Space Telescope. We obtained Advanced Camera for Surveys Solar Blind Channel far ultraviolet low-resolution spectra that show oxygen line emission both in and out of eclipse. We also used the Wide-Field and Planetary Camera-2 and searched for broad-band optical emission from fluorescence of the surface material, arising from the very high level of incident energetic particle radiation on ices and potentially organic substances. The high-energy particle radiation at the surface of Europa is extremely intense and is responsible for the production of a tenuous oxygen atmosphere and associated FUV line emission. Approximately 50% of the oxygen emission lasts at least a few hours into the eclipse. We discuss the detection limits of the optical emission, which allow us to estimate the fraction of incident energy reradiated at optical wavelengths, through electron-excited emission, Cherenkov radiation in the ice and fluorescent processes.

Type
Research Article
Copyright
Copyright © Cambridge University Press 2010

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