Callisto: Dirty Battered Iceball (Image: Kevin M. Gill/NASA)
Gaze up at the night sky and picture a world bigger than Mercury but lost well out of sight. Jupiter’s moon Callisto, cratered and icy, could conceal mysteries beneath its battered surface….
NASA’s picture of the Day, September 1: Jupiter’s Moon Callisto, a dirty iceball, may hide ocean beneath its surface
