The ice around Mercury's poles is in permanently shadowed craters. The polar aspect is what allows there to be substantial permanently shadowed areas (because

The ice around Mercury's poles is in permanently shadowed craters. The polar aspect is what allows there to be substantial permanently shadowed areas (because the sun never rises high in the sky). Ref: http://www.space.com/27450-messenger-mercury-water-ice-photos.html http://www.space.com/27450-messenger-mercury-water-ice-photo...