A true-colour image of the Nereidum Mountain Range in the southern hemisphere of Mars captured by the High Resolution Stereo Camera (HRSC) aboard ESA's Mars Express orbiter in 2015. The recently reprocessed image reveals evidence of a variety of geological processes that have shaped the area north of the large Argyre impact basin over billions of years.
Branch-like structures of valleys were carved into the slopes either by the melting snow and ice or runoff from rain in the early period of Mars’ evolution when the planet had abundant water resources.
Inside the craters in the image, one can see deposits, in some cases concentric, probably created by the sublimation of ice that used to cover the region in the past. Scientists believe water ice might still be present in the region deep under the surface.
Mass wasting deposits clearly visible in the canyons captured in this image are also a result of glacial processes that had taken place in the area in the past.
The dark brown streak on the left-hand side of the image represents dune fields created by the effects of wind as it transports sand grains over large distances on the surface of Mars. On the north-facing slope of the ridge between the northern part of the dune field and the large filled crater towards the south, one can clearly see recently created alcoves and gullies. These structures are often linked to the melting of ground ice and could point to still existing water ice deposits in the subsurface.