This image shows two craters, both approximately the same diameter (not quite 3 kilometers, or about 1.8 miles), but quite different in appearance otherwise.
The slightly smaller crater to the south seems to have a sharper rim and steeper sides than its partner to the north, which also appears to contain more small craters inside it and along its rim. The interior of the northern crater, in particular its south-facing wall, appears to have a similar texture to the ejecta around the southern crater. This is the second image in a stereo pair (the first is ESP_019346_1690 ), so we have an anaglyph of these craters.
Although it would require a digital terrain model and more analysis to be certain, in the anaglyph it appears that the southern crater has a higher rim and a deeper center than the northern crater. All these signs point to the northern crater being quite a bit older than the southern crater, rather than the two craters forming in the same impact event. For an example of two craters that might have formed at the same time (see ESP_020894_1395 ).
Compare the similarity of those two craters with the disparate appearance of the ones in this image.
Written by: Nicole Baugh (audio by Tre Gibbs) (13 June 2012)
This is a stereo pair with ESP_019346_1690 .
More info and image formats at http://hirise.lpl.arizona.edu/ESP_020190_1690
Image: NASA/JPL/University of Arizona