NASA LRO Image of the Moon: Smooth Ejecta




Grooved surface created in an instant by an impact event. The linear pattern is radially symmetric around the parent crater; the parent crater must be very young as very few craters dot the ejecta blanket! LROC NAC M171788458RE, image width is 650m [NASA/GSFC/Arizona State University].

When an impact event deposits an ejecta blanket, nearby craters of all sizes are buried or modified. Larger craters may be preserved, while smaller examples are obliterated. In the case of today's Featured Image, a nearby impact covered the area and erased any craters that previously existed. Currently only small impact craters dot the landscape, but must have been emplaced after the ejecta blanket was deposited. In fact many of these small craters may be auto-secondaries; craters that formed as late stage blocks of ejecta landed on the just formed ejecta (all from the same impact event). Because these impacts are so few, and so small, the ejecta (and corresponding parent crater) must be very young.

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