New horizons mapping of Europa and Ganymede.

Evidence for Europa-like tectonic resurfacing styles on Ganymede

[1] Very high-resolution imaging and stereo topographic data obtained during the Galileo G28 encounter with Ganymede show 1) evidence for Europa-like, crustal spreading and resurfacing to form portions of the bright terrain, and 2) bright terrain that appears smooth at Voyager resolution (and thus a strong candidate for cryovolcanism) but instead is tectonically deformed and lacks embayment rel...

Cartographic and Topographic Mapping of the Icy Satellites of the Outer Solar System

Cartographic and topographic mapping of the major satellites of the Outer Solar System has been in progress since the late 1980’s, beginning with Voyager image data, and incorporating Galileo and recently Cassini imaging data as released to the public. Global image mosaics, based on cartographic control nets, have been produced for all these satellites. In addition, digital topographic maps hav...

A Search for a Sodium Atmosphere around Ganymede

Long-slit high-resolution spectra have revealed that Ganymede has an atmospheric sodium column density, between a distance of 7800 and 15600 km from the satellite surface, of less than 1 10 8 atoms cm ?2 , a factor of 13 times smaller than the sodium density in the atmosphere of Europa at the same distance. Assuming similar processes creating sodium on both Europa and Ganymede, we estimate that...

Rampart craters on Ganymede and Europa: implications for fluidized ejecta emplacement

Condensed O2 on Europa and Callisto

High signal-to-noise ratio spectra of Europa and Callisto’s trailing side show a 0.3% deep 5771 Å absorption band due to condensed O2 at the same wavelength as a stronger band previously identified on Ganymede. Excellent longitudinal coverage for Europa shows that unlike Ganymede, where the band is much stronger on the trailing side, Europa shows no significant longitudinal variation in the O2 ...