These two craters show distinct bright layers around their rims. The crater on the top formed after the other, and its rim is sharp and less degraded, showing that it is younger.
At the juncture of the two craters is a landslide ( flowing into the top crater ) that probably formed during the late stages of the top crater’s own formation or perhaps shortly after that.
The material that looks rough surrounding both craters is called ejecta, which is material that the impacts excavated.
Written by: Kelly Kolb (22 October 2008)
More info and image formats at http://hirise.lpl.arizona.edu/PSP_009694_1545
Image: NASA/JPL/University of Arizona