Meteorites from Mars By mid-2001, 25 SNC meteorites are known that are thought to come from Mars. How we know this is a bit of a detective story! The SNCs are igneous rocks, named after the type specimens of the three original sub-groups (Shergotty, Nakhla and Chassigny). Collection of additional martian meteorites from Antarctica and the Sahara desert has extended the number of sub-groups to five, including the unusual rock ALH 84001. The different sub-groups are igneous rocks that formed in different locations at, or below the martian surface. The groups have different mineralogies and chemistries, and cannot all have come from a single impact event. At least three craters, with minimum diameters of ~ 12 km, are required to produce the variety of martian meteorite types now known.

This is one of a small number of meteorites recovered in the Antarctic with trapped gas isotopic abundances very close to those measured by the Viking Lander in 1976.