Recent small craters discovered by the High Resolution Imaging Science Experiment camera on NASA's Mars Reconnaissance Orbiter expose buried ice in the middle latitudes of Mars. This ice is a record of past climate change. Not stable today, it was deposited during a period of different obliquity, or tilt, of the planet's axis.
This image is one product from HiRISE observation ESP_011337_2360 . Other image products from this observation are available at http://hirise.lpl.arizona.edu/ESP_011337_2360. (Image: ESP_011337_2360; (Reference: Byrne et al., 2009).