Geologic History Revealed in Valles Marineris

An enhanced-color image from NASA's Mars Reconnaissance Orbiter (MRO) reveals bedrock that is several kilometers below the top of the giant Valles Marineris canyons.

The upper layers have relatively little diversity of colors and textures, but deeper levels show more complex processes. The upper layers could be mostly volcanic while the lower layers were influenced by the period of heavy bombardment and greater interactions with water.

https://photojournal.jpl.nasa.gov/catalog/PIA22238