Collapse Pit in Tractus Fossae (edm - Vertical View - Natural Colors; credits: Lunar Explorer Italia)

This HiRISE image shows a collapse pit in Tractus Fossae, a Region of large Ridges and Troughs created by Tectonic Activity.
The Fossae occur on the Tharsis Volcanic Rise, a giant region of enhanced volcanic activity that includes the 3 large volcanoes Ascraeus Mons, Pavonis Mons and Arsia Mons.

The Pit in this image has very steep walls, and so only a narrow arc is illuminated by Sunlight. The rest of the Pit is in dark shadow.
However, a stretched version of the image shows details of the pit floor, due to a small amount of scattered Sunlight.
Pits like this form by collapse into underground voids, such as those left by propagating magma-filled dikes.
They may sometimes have overhanging walls, although in this case the walls can be seen and appear nearly vertical. Some similar features are found on Earth: Devil’s Throat, in Hawaii, is one example.
Other similar examples have been imaged on Mars as well.