Water in a martian desert

1 August 2013 - Craters once brim-full with sediments and water have long since drained dry, but traces of their former lives as muddy lakes cling on in the martian desert. The images were taken on 15 January by ESA's Mars Express, and feature a region just a few degrees south of the equator within the ancient southern highlands of Mars. The unnamed region lies immediately to the north of an ancient riverbed known as Tagus Valles and east of Tinto Valles and Palos crater that were presented in an earlier release. The 34 km-wide crater in the top left of the main images perhaps draws most attention with its chaotic interior. Here, broad flat-topped blocks called mesas can be found alongside smaller parallel wind-blown features known as yardangs. Both mesas and yardangs were carved from sediments that originally filled the crater, deposited there during a flood event that covered the entire scene. Over time, the weakest sediments were eroded away, leaving the haphazard pattern of stronger blocks behind.