EUROPA - INITIAL GALILEO GEOLOGICAL OBSERVATIONS

Images of Europa from the Galileo spacecraft show a surface with a com plex history involving tectonic deformation, impact cratering, and pos sible emplacement of ice-rich materials and perhaps liquids on the sur face, Differences in impact crater distributions suggest that some are as have been resurfaced more recently than others; Europa could experi ence current cryovolcanic and tectonic activity. Global-scale patterns of tectonic features suggest deformation resulting from non-synchrono us rotation of Europa around Jupiter. Some regions of the lithosphere have been fractured, with icy plates separated and rotated into new po sitions. The dimensions of these plates suggest that the depth to liqu id or mobile ice was only a few kilometers at the time of disruption. Some surfaces have also been up-warped, possibly by diapirs, cryomagma tic intrusions, or convective upwelling. In some places, this deformat ion has led to the development of chaotic terrain in which surface mat erial has collapsed and/or been eroded. (C) 1998 Academic Press.