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Cassini/VIMS observation of an Io post-eclipse brightening event |
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| Authors: | G Bellucci E D'Aversa D Cruikshank RN Clark D Matson TB McCord PD Nicholson the Cassini VIMS Team |
| Institution: | a Istituto di Fisica dello Spazio Interplanetario, INAF, Via Fosso del Cavaliere 100, 00133 Roma, Italy b NASA Ames Research Center, Moffett Field, CA, USA c Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA d US Geological Survey, Box 25046 Denver Fed. Ctr., Denver, CO 80025, USA e Lunar and Planetary Lab and Stewart Observatory, University of Arizona, Tucson, AZ 85721-0092, USA f Department of Earth and Space Sciences, University of Washington, Box 351310, Seattle, WA 98195, USA g Astronomy Department, Cornell University, Ithaca, NY 14853-6801, USA |
| Abstract: | During the Cassini-Jupiter flyby, VIMS observed Io at different phase angles, both in full sunlight and in eclipse. By using the sunlight measurements, we were able to produce phase curves in the visual through all the near infrared wavelengths covered by the VIMS instrument (0.85-5.1 μm). The phase angle spanned from ∼2° to ∼120°. The measurements, done just after Io emerged from Jupiter's shadow, show an increase of about 15% in Io's reflectance with respect to what would be predicted by the phase curve. This behavior is observed at wavelengths >1.2 μm. Moreover, just after emergence from eclipse an increase of about 25% is observed in the depth of SO2 frost bands at 4.07 and 4.35 μm. At 0.879<λ<1.04 μm the brightening is 10-24%. Below λ=0.879 μm the brightening, if present, should be less than the precision of our measurements (∼5%). Apparently, these observations are not explained neither by a diverse spatial distribution of SO2 on the Io' surface nor by atmospheric SO2 condensation on the surface during the eclipse. |
| Keywords: | Io Atmosphere Infrared observations Satellites of Jupiter |
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