Remnants of Lost Geology

In this NASA Mars Odyssey image of eastern Arabia Terra, remnants of a once vast layered terrain are evident as isolated buttes, mesas, and deeply-filled craters. The origin of the presumed sediments that created the layers is unknown, but those same sediments, now eroded, may be the source of the thick mantle of dust that covers much of Arabia Terra today.

http://photojournal.jpl.nasa.gov/catalog/PIA04400