Pits, Hollows and Viscous Flow

The mid-latitudes of Mars are draped with deposits of water ice and dust on the order of tens of meters thick. The deposits are preserved to varying degrees, depending on latitude and the degree of dust cover that insulates and protects the ice from subliming away. These mantling deposits are thought to have been mobilized from the polar caps and redeposited from the atmosphere millions of years ago during periods when Mars' axial tilt was higher than it is today. The floor of this crater appears filled with such deposits, as evidenced by surface textures such as pits, hollows, grooves, and other small filled craters. The material has undergone viscous flow, resulting in many curved ridges. Much of the original ice may have been lost to sublimation, but it is likely that a significant amount of ice remains. https://photojournal.jpl.nasa.gov/catalog/PIA23582