Hole in OneSunlight casts a crescent shadow on the floor of an underground cavern in a recently released picture of a Martian "skylight." This round opening likely leads to a lava tube, which is created when lava solidifies on the surface but keeps flowing underground. Eventually the lava drains away, leaving an empty cave.Snapped by NASA's Mars Reconnaissance Orbiter, the picture revealed that the skylight is 115 feet (35 meters) across. The shadow helped scientists calculate that the cave floor is about 65 feet (20 meters) below the surface.
Image courtesy U-Arizona/NASA

Space Pictures This Week: Mars Pit, Warped Galaxy, More

NASA probes a Martian "skylight," a galaxy gets bent, a meteor falls on the Andes, and more in the week's best space pictures.

Published August 26, 2011