The UA-run HiRISE camera on the Mars Reconnaissance Orbiter spotted this unusual "bulls-eye" crater on Mars. Project member Sarah Milkovich told Space.com that it could be either due to uneven erosion due to weak layers underlying the crater or a fortuitous second impact right in the center of the larger crater.
[Photo credit: NASA/JPL/University of Arizona]
Phil at Bad Astronomy posted about this same crater with some interesting extra details and ideas that make me think the second impact idea is not what happened
ReplyDeletehttp://blogs.discovermagazine.com/badastronomy/2010/07/30/wham-bulls-eye/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed:+BadAstronomyBlog+(Bad+Astronomy