Cave entrance on the flank of Arsia Mons

Cave entrance on the flank of Arsia Mons
Cave entrance on the flank of Arsia Mons In this HiRISE image captured on May 7, 2007, a black spot mars the flank of Arsia Mons. The spot is most likely a skylight onto a subterranean cavern. NASA / JPL-Caltech / U. Arizona