<p>Secondary Craters: 
Secondary impact craters are both interesting and vexing, but can be used to constrain the age of the surface where they fell.
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NASA/JPL/University of Arizona (<a rel="nofollow" class="external text" href="http://www.uahirise.org/ESP_046876_1465">www.uahirise.org/ESP_046876_1465</a>)
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/71688597@N05">UAHiRISE (NASA)</a>
2016-12-16 14:17
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