Surrounding the uplifted bedrock in the center of this large crater is mottled terrain. What possibly caused this?
The floor of the crater might be the result of icy flows. Perhaps an ancient aquifer system was exposed at the time of the impact resulting in the incredible mottled floor we see now, which appears different from the uplifted central peak.
This caption is based on the original science rationale.
Written by: HiRISE Science Team (audio by Tre Gibbs) (30 January 2013)
More info and image formats at http://hirise.lpl.arizona.edu/ESP_024870_2080
Image: NASA/JPL/University of Arizona