Martian Meteorite

Over 30 of the meteorites found on Earth almost certainly came from Mars (see http://www.imca.cc/mars/martian-meteorites.htm and http://www2.jpl.nasa.gov/snc/). All but one belongs to the group known as SNC meteorites, which includes the shergottites, nakhlites, and chassignites. SNC meteorites contain minerals that crystallized within the past 1.35 to 0.15 Ga, making them much younger than any other known achondrites. The one oddball is an orthopyroxenite. Trapped gases within several SNC meteorites exactly match the composition of the Martian atmosphere as measured by the Viking landers, confirming its place of origin.


Modified from image source: http://www.imca.cc/mars/martian-meteorites.htm.

Oddly, the orthopyroxenite, ALH 84001, became the center of controversy in 1996 when a group of NASA scientists claimed it contained fossil bacteria. It represents a deeper part of Mars, and has a much older crystallization age of 4 Ga. The Lafayette meteorite, a nakhlite, contains the highest percentage of water of all Martian rocks.