This image shows many small craters over a larger degraded one in the northern lowlands. These small craters are smoother and shallower than their counterparts closer to the equator.

Scientists believe this difference is a result of impact into a region with subsurface ice, which sublimates when exposed to the Martian atmosphere. This causes the crater to gradually expand and flatten after impact.

ID: ESP_044037_2345
date: 18 December 2015
altitude: 306 km

https://uahirise.org/hipod/ESP_044037_2345
NASA/JPL-Caltech/UArizona
#Mars #science #NASA