27. Dionysius
(Real Color)
The crater Dionysius (3°N, 17°E; western edge of Mare Tranquillitatis;
18 kilometers in diameter) shows striking contrasts in albedo. The outside
of the crater is a very bright halo in its near-rim field, while farther
out, darker material is exposed, including rare dark rays. Crater deposits
on the left side of this mosaic are on light Cayley plains of highland
composition, while deposits on the right side are on the basalts of Mare
Tranquillitatis.