Big ice may explain Mars’ double-layer craters

An odd type of crater

Double-layer ejecta craters could form when ejected material slides down steep crater walls and across ice, forming a top layer. Striations, common in landslides on Earth, radiate out from the crater rim. Credit: NASA

Brown planetary geologists have an explanation for the formation of more than 600 “double-layer ejecta” (DLE) craters on Mars. The Martian surface was covered with a thick sheet of ice at impact. Ejected material would later slide down steep crater sides and across the ice, forming a second layer.