NASA/JPL/University of Arizona
Collapse Pit in Tractus Fossae
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 three 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.

Map projected reduced-resolution (PNG)

Full resolution JPEG2000

All of the images produced by HiRISE and accessible on this site are within the public domain: there are no restrictions on their usage by anyone in the public, including news or science organizations. We do ask for a credit line where possible:
NASA/JPL/University of Arizona
Left observation

Right observation

Contrast stretch

Convergence angle
15.6 degrees

Image lines

Line samples

About anaglyph products (PDF)

NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA’s Science Mission Directorate, Washington. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona.