This isn’t just any weird hole in the ground , it’s a cavern — a space cavern on Mars. And it, and others like it, could have some interesting applications for how to look for extraterrestrial life. The picture was shot by the Mars Reconnaissance Orbiter using its HiRISE camera. By looking at how the shadows fall, scientists were able to estimate that it is over 65 feet deep.
So just what does all this have to do with the search for life on Mars? Perhaps a lot. Because these caves lie deep below the surface, they aren’t exposed to the same harsh barrage of the elements that the Martian surface weathers. This, says NASA, means that they could be “relatively good candidates” for searching out life on Mars. Via Is this hole in the ground our best shot at finding life on Mars?.