This image shows two small craters , just touching on their rims, in the much larger Ptolmaeus Crater, which is located in the Martian Southern hemisphere. These craters are called “tangential craters.”
The more degraded and filled-in crater is approximately 3 kilometers in diameter, and there is an unusual feature near the center. A closeup shows up the feature is approximately 76 meters wide and 164 meters long. This feature is also possibly a substantially oblique impact crater, but its origin remains unknown.
Written by: Livio Tornabene and Kayle Hansen (audio: Tre Gibbs) (4 February 2015)
More info and image formats at http://hirise.lpl.arizona.edu/ESP_020065_1335
Image: NASA/JPL/University of Arizona