A Martian meteorite is a rock that was pushed off the surface of Mars by a big impact. It traveled in space for many years and then landed on Earth.
Less than 1% of all known meteorites are Martian. Scientists know they are Martian because they have the same gas mix that NASA found on Mars.
There are three main types: Shergottites, Nakhlites and Chassignites. Shergottites are the most common. The olivine, basaltic and lherzolitic sub-types are all part of this family.