The pits visible here aren’t impact craters . The material they’re embedded into is ejecta (stuff thrown out of an impact crater when it forms) from a large crater called Hale which is not seen in this image.
Substances called “volatiles”—which can explode as gases when they’re quickly warmed by the immense heat of an impact—exploded out of the ejecta and caused these pits. Unrelated sand dunes near the top of the image have since blown over portions of the pits.
Written by: Kirby Runyon (audio: Tre Gibbs) (28 January 2015)
This is a stereo pair with ESP_039801_1445 .
More info and image formats at http://hirise.lpl.arizona.edu/ESP_039524_1445
Image: NASA/JPL/University of Arizona