Not really, but it sure seems like it! A 900-foot-wide hole in the Tractus Fossae region of Mars drops down into blackness in this photo by the HiRISE camera on the Mars Reconnaissance Orbiter…it looks like an entrance to a cave or “bottomless pit” but is actually just a very steep-walled depression, formed by the collapse of an underground lava tunnel. Pits like this exist on Earth too…such as Hawaii’s Devil’s Throat.
By adjusting the photographic levels of the image data details of the pit’s walls and bottom can be seen.
The Tractus Fossae region contains evidence of much volcanic activity, including three large volcanoes. All of which, like every volcano on Mars, are long extinct.
Image credit: NASA/JPL/University of Arizona