Martian meteorite

A meteorite blasted from Mars by an impact and later recovered on Earth. Its minerals and trapped gases provide direct samples of Martian crust and mantle.

Impact event: A collision in which a body strikes a planetary surface at high speed. An impact can excavate Martian rock and accelerate fragments beyond the planet’s escape velocity.
Martian meteorite classification: The grouping of Martian meteorites by mineralogy, chemistry, and geological history. Classification organizes the diverse rock types recovered from Mars.
ALH 84001: A Martian meteorite discovered in Antarctica in 1984, notable for ancient carbonate deposits and a disputed claim of fossil evidence. Its mineral features sparked a high-profile debate about possible ancient life on Mars.
Martian geochronology: The study of the timing of geological events on Mars using dated rocks and minerals. Meteorite ages help establish when Martian crust formed, melted, or was reset by impacts.
ALH 84001 fossil controversy: The debate over whether structures and minerals in ALH 84001 record ancient Martian microorganisms. The meteorite’s proposed biological signatures remain disputed and illustrate limits of interpreting isolated samples.
Mars escape velocity: The minimum speed needed for an object to escape Mars without further propulsion. Ejected fragments must reach this speed to leave Mars and begin an interplanetary journey.
Shergottite–nakhlite–chassignite group: The three principal groups of Martian igneous meteorites, commonly abbreviated SNC. These groups provide the traditional framework for describing many Martian meteorites.
Shergotty meteorite: A basaltic Martian meteorite that fell in India in 1865 and gave its name to the shergottite class. This fall established the name for the most abundant Martian meteorite group.
Oxygen isotope ratio: The relative abundances of oxygen isotopes in a material, used to investigate its origin and history. Isotope patterns help distinguish Martian rocks from terrestrial rocks and other meteorite sources.
Martian meteorite ejection age: The time elapsed since a Martian rock was blasted from the planet, estimated using cosmic-ray-produced isotopes. Different exposure histories constrain which impact events could have launched known specimens.

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