Young craters on smooth plains

Young craters on smooth plains

. The smooth-plain terrain of Mercury is a possible example of a secondary crust of volcanic origin; but unlike the dark lunar maria the smooth terrain on Mercury is light in color. It was created after the heavy bombardment that excavated the older craters on the planet, but before the younger craters that are superposed on the smooth plains. The largest young crater shown here is about 100 thousand meters in diameter; such large craters have central peaks, flat floors, terraced walls, radial ejecta deposits and surrounding fields of secondary craters. The smooth plains shown here, in a Mariner 10 image, have well-developed ridges. (Courtesy of JPL and NASA.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University