The High Resolution Imaging Science Experiment (HiRISE) camera is a 0.5 meter reflecting telescope onboard the spacecraft Mars Reconnaissance Orbiter (MRO). Resolution is about 1 foot. Earlier this year, the HiRISE camera found a pit (shown above) on the slopes of the Pavonis Mons volcano.
A detailed view of the pit on the Pavonis Mons volcano on Mars. The skylight is 35 meters (115 feet) in diameter). The shadow cast on the floor of the cave suggests a depth of 20 meters (65 feet) according to scientists.