Mars Caves?Looking like space slug hidey-holes, huge pits gouge a bright, dusty plain near the Martian volcano Ascraeus Mons in a picture taken between October 1 and November 1 by NASA's Mars Reconnaissance Orbiter (MRO).
Released in December, the image is among a series of new views snapped by MRO's HiRISE camera that show intriguing geological features on Mars. Each image covers a strip of Martian ground 3.7 miles (6 kilometers) wide and can reveal a detail about as small as a desk—and so far no sign of Star Wars monsters.MRO's sister orbiter, Mars Odyssey, first noticed the two deep pits—which are about 590 feet (180 meters) and 1,017 feet (310 meters), respectively—a year earlier using its infrared camera, THEMIS. (Related: "Seven Great Mars Pictures From Record-Breaking Probe.")"When compared to the surrounding surface, the dark interiors of the holes gave off heat at night but were cool by day," said Alfred McEwen, principal investigator on the HiRISE camera."So we then decided to target these with MRO because this thermal information may be evidence for these being caves—but the jury is still out on that."(See "Mars Has Cave Networks, New Photos Suggest.")The MRO has been studying Mars since 2006, beaming back more data than all other past and current missions to the planet combined. —Andrew Fazekas

Image courtesy NASA/JPL/University of Arizona