McEwen, A., Geissler, P., Turtle, E., Keszthelyi, L., Belton, M., Porco, C., Klemaszewski, J., Williams, D., Spencer, J., Lopes, R., Pappalardo, R., and the GLL Team (2001). "Recent Galileo and Cassini Observations of the Galilean Satellites." American Astronomical Society, DPS meeting #33, #2.05.


Abstract
Galileo has completed several orbits of Jupiter in the past year, Cassini passed by on its way to Saturn, and a suite of new observations of the Galilean satellites have been acquired. Galileo data obtained of Callisto's surface during the 30th orbit (May 2001) show bright, icy regions with high-standing knobs and spires tens to hundreds of meters tall (Klemaszewski et al., this conference). The gradual loss of ice by sublimation may liberate non-ice material which slides down-slope due to gravity, piling up at the base of the spires. Galileo acquired color observations of Ganymede's polar cap in orbit G29 (the joint encounter). Cassini captured several sequences of images showing Io, Europa, and Ganymede while eclipsed by Jupiter (Geissler et al., this conference). The images show that Europa is brightest along its limb, suggesting auroral emissions. The Io data have been assembled into color time-lapse sequences showing motion of the equatorial sulfur dioxide and oxygen glows in response to the changing orientation of the Jovian magnetic field. The eclipse data also show temporal variations in the temperatures at Pele, which may be a vigorously overturning lava lake (Radebaugh et al., this conference). The joint Cassini and Galileo images of Io revealed a large (400 km) plume over Tvashtar Catena. The Galileo spacecraft flew through the volume of this (former?) plume in the I31 flyby (August 6). When the imaging data has been fully returned we may be able to say whether the Tvashtar plume was active, but there are several other large new plumes and plume deposits. The Galileo PPR instrument mapped Io's thermal emission in detail in I31, which will provide new information on the global heat flow and processes at Loki. NIMS acquired a wealth of new data in I31 and mapped several intense hot spots (Lopes et al., this conference). SSI failed to acquire any high-resolution images in I31 due to radiation-sensitive electronics, but will try again with a new strategy in I32 (October 14).