Nestled within the fractured rim of a vast impact basin on Mars are valley floors dusted in frost. At 2200 km wide and up to 9 km deep, the Hellas Basin is the largest impact crater on Mars. This scene, captured on 6 December 2015 by ESA’s Mars Express, focuses on a portion of the western rim of the basin.
This region spans a height difference of over 6000 m, stepping down like a staircase from the basin’s fractured, terraced rim to its flat, low-lying floor that is covered in frost or ice.
The surface expression of numerous valley-like features can be seen below the icy covering, indicating a flow of material towards the catchment areas on the floor of Hellas. [More at link]