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the ionosphere of europa from galileo radio occultationsThe Galileo spacecraft performed six radio occultation observations of Jupiter's Galilean satellite Europa during its tour of the jovian system. In five of the six instances, these occultations revealed the presence of a tenuous ionosphere on Europa, with an average maximum electron density of nearly 10(4) per cubic centimeter near the surface and a plasma scale height of about 240 +/- 40 kilometers from the surface to 300 kilometers and of 440 +/- 60 kilometers above 300 kilometers. Such an ionosphere could be produced by solar photoionization and jovian magnetospheric particle impact in an atmosphere having a surface density of about 10(8) electrons per cubic centimeter. If this atmosphere is composed primarily of O2, then the principal ion is O2+ and the neutral atmosphere temperature implied by the 240-kilometer scale height is about 600 kelvin. If it is composed of H2O, the principal ion is H3O+ and the neutral temperature is about 340 kelvin. In either case, these temperatures are much higher than those observed on Europa's surface, and an external heating source from the jovian magnetosphere is required.
Document ID
Document Type
Reprint (Version printed in journal)
Kliore, A. J.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Hinson, D. P.
Flasar, F. M.
Nagy, A. F.
Cravens, T. E.
Date Acquired
August 22, 2013
Publication Date
July 18, 1997
Publication Information
Publication: Science
Volume: 277
Issue: 5324
ISSN: 0036-8075
Subject Category
Lunar and Planetary Science and Exploration
Distribution Limits
Galileo Project
long duration
Flight Experiment