Pit in Tolstoj Basin

The Tolstoj basin is located in Mercury's southern hemisphere, and is 355 km (220 miles) in diameter. This oblique image shows an elongate pit inside Tolstoj, a basin whose floor appears to have been flooded by lavas. The pit lacks the raised rim of an impact crater, and may have formed when magma withdrew from a shallow chamber, causing an unsupported area of the surface to collapse. The low-angle lighting in this image hides the floor of the pit, making it appear much deeper than it actually is. The pit is aligned approximately north-south.

Date acquired: January 11, 2012
Image Mission Elapsed Time (MET): 234752446
Image ID: 1251011
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: -16.97°
Center Longitude: 198.1° E
Resolution: 99 meters/pixel
Scale: This image shows a field of view approximately 150 km (93 miles) across
Incidence Angle: 84.8°
Emission Angle: 58.6°
Phase Angle: 135.6°

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

Note: These types of pit craters are fairly commonplace on Mars; for example, see Crater and Skylight on Pavonis Mons and Dark Rimless Pits in the Tharsis Region. That similar features should be present on Mercury is, to me, not surprising at all.