The European Space Agency has released new images of the Hellas basin, which formed around four billion years ago when a small asteroid crashed into the Red Planet, creating an impact crater 1,400 miles wide and 26,465 feet deep.
The images, taken by the high-resolution stereo camera on the ESA's Mars Express, feature a portion of the Hellespontus Montes, a rough chain of mountain-like terrain that runs around the rim of the basin located in the southern hemisphere.
In the foreground of this perspective view (photo above), just outside the rim, you can see a crater with a particularly interesting feature: wrinkles that form a roughly concentric pattern, with ever-smaller arcs towards the center. This type of feature is known as "concentric crater fill," and is thought to be associated with snowfall and freezing cycles in an earlier and wetter period of Martian history.
Once inside the crater, the snow was trapped and soon covered by surface dust before compacting to form ice. The number of concentric lines indicate this process underwent many cycles. It's possible that ice may be hidden just a few hundred feet beneath the surface debris.
This next image shows the same terrain viewed from above. The Hellespontus Montes runs roughly half way through the image from the edge of the large crater on the left towards the right hand side of the scene. Intricate valleys lead down from the rocky rim and weave through and across the smoother surrounding plains.
A color-coded topography map offers additional perspective: white and red show the highest terrains, while blue and purple show the deepest.