Footprints of a martian flood
|Arda Valles [Credit: ESA/DLR/FU Berlin]|
Vast volumes of water once flowed from the southern highlands, carving Ladon Valles and ponding in the large Ladon Basin seen in this image.
The plan views show the striking dendritic drainage pattern of the valleys (left). Many contributing streams merge into tributaries of the main channels before flowing down into the smooth-floored impact basin towards the right.
|Arda Valles context [Credit: NASA MGS MOLA Science Team]|
To the top right of the scene, the surface has also broken up into a number of giant polygons, likely linked to the loss of underground ice and the slow evaporation of water that was once ubiquitous in this area.
|Arda Valles perspective [Credit: ESA]|
Some of the fractures seem to join the central crater to the smoother basin floor, particularly evident in the perspective view. They could be a later manifestation of stresses due to subsidence or compaction of surface materials.
Finally, in the lower centre of the image, just above the crater at the bottom of the scene and towards the end of the dendritic channels, light-toned and layered deposits have been identified. These are clay minerals, known to be formed in the presence of water.
Source: European Space Agency [February 18, 2016]