NASA Mars MRO HiRise Image: Late winter on south-facing slopes

Image Credit: NASA MRO.

An image of Mars taken by the HiRISE instrument on NASA's Mars Reconnaissance Orbiter shows frost or ice (white areas) persisting in late winter only on south-facing slopes that have not received much direct sunlight.

Ridges between gully alcoves receiving more light appear reddish and mostly free of frost. New gully activity is not readily detectible in this image.

In some years, the frost (up to roughly 3.3 feet or 1 meter thick) triggers avalanches, although not in most years.

The frost here consists of mostly carbon dioxide (dry ice), but also contains small amounts of water ice.