Uncovering a Dark Past - Nasa Messenger Image: Release Date 1 March 2012

Date acquired: December 01, 2011 Image Mission Elapsed Time (MET): 231267850 Image ID: 1082997 Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS) Center Latitude: -45.06° Center Longitude: 135.3° E Resolution: 102 meters/pixel Scale: Sher-Gil crater is about 76 km (47 mi.) in diameter Incidence Angle: 59.6° Emission Angle: 15.9° Phase Angle: 65.0° Of Interest: Impact craters serve as probes into a planet's subsurface, excavating and exposing material from depth that would be otherwise unobservable. Thus the study of impact crater deposits can help to elucidate the geological history of the target region. In this image, the crater Sher-Gil has exposed low-reflectance material, particularly in its eastern wall and at two concentrated points on the north and south rim. Younger, bright features called hollows dot the dark parts of the crater. This image was acquired as part of MDIS's high-resolution stereo base map. The stereo base map is used in combination with the surface morphology base map to create high-resolution stereo views of Mercury's surface, with an average resolution of 250 meters/pixel (0.16 miles/pixel or 820 feet/pixel) or better. During MESSENGER's one-year mission, the surface morphology base map is acquired during the first 176 days, and the second 176 days are used to acquire the complementary stereo base map, which includes the image here.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington