Another large cave opening, also known as a “skylight” entrance, has been found by the Mars Reconnaissance Orbiter, on the slopes of the Pavonis Mons volcano. This has to be one of the best I’ve seen so far; it’s about 35 metres (115 feet) across and 20 metres (65 feet) deep. The hole is at the bottom of a much larger crater-like feature (the origin of which is unknown according to the HiRISE web site). Click image for larger version. If only we could take a look inside!