Among Martian meteorites, only ALH 84001 and NWA 7034 have radiometric ages older than about 1400 Ma (Ma = million years).
A Martian meteorite is a rock that formed on the planet Mars and was then ejected from Mars by the impact of an asteroid or comet, and finally landed on the Earth.
Of over 61,000 meteorites that have been found on Earth, 224 were identified as Martian as of January 2019 In October 2013, NASA confirmed, based on analysis of argon in the Martian atmosphere by the Mars Curiosity rover, that certain meteorites found on Earth thought to be from Mars were indeed from Mars.
Several scientists suggested these characteristics implied the origin of SNC meteorites from a relatively large parent body, possibly Mars.
These trapped gases provided direct evidence for a Martian origin.
If they were from another planetary body, it would have to be substantially identical to Mars as it now is understood."The Martian meteorites are divided into three groups (orange) and two grouplets (yellow).
SHE = Shergottite, NAK = Nakhlite, CHA = Chassignite, OPX = Orthopyroxenite (ALH 84001), BBR = Basaltic Breccia (NWA 7034).
The term does not refer to meteorites found on Mars, such as Heat Shield Rock.
On January 3, 2013, NASA reported that a meteorite, named NWA 7034 (nicknamed "Black Beauty"), found in 2011, in the Sahara desert, was determined to be from Mars and found to contain ten times the water of other Mars meteorites found on Earth.
They have isotope ratios that are said to be consistent with each other and inconsistent with the Earth.
The names derive from the location of where the first meteorite of their type was discovered.
In 2000, an article by Treiman, Gleason and Bogard gave a survey of all the arguments used to conclude the SNC meteorites (of which 14 had been found at the time) were from Mars.