Impacts Into Ancient Martian Ice Implicated In Double-Layered Ejecta Craters

There is a possible new explanation for a mysterious type of crater on the surface on Mars.  Double-layered ejecta craters (DLEs) are surrounded by debris excavated by an impactor  just like other craters. What makes DLEs different is that the debris forms two distinct layers — a large outer layer with a smaller inner layer sitting on top. These distinctive craters were first documented in data returned from the Viking missions to Mars in the 1970s, and scientists have been trying ever since to figure out how the double-layer pattern forms. A new study suggests that DLEs are the result of impacts onto a surface that was covered by a layer of glacial ice tens of meters thick. read more

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