Meteorites from Mars!

  • young ages and trapped atmosphere
  • 12 igneous meteorites of 5 distinct types
  • ejection from Mars by impact
  • Twelve unusual meteorites are almost certainly pieces of Mars that were blasted off the red planet by meteoroid impact. They have been called SNC meteorites after the three type samples, Shergotty, Nakhla, and Chassigny, or now simply martian meteorites. All twelve meteorites are igneous rocks crystallized from molten lava in the crust of a parent body. They are, however, distinct from typical igneous meteorites from asteroids in ways that suggest that the SNC meteorites come from a much larger body, a planet. All but one of these meteorites are very young (less than 1.3 Ga) compared to ancient ages for other igneous meteorites (about 4.5 Ga). They also have higher oxygen fugacities and contents of water and other volatiles, contain minerals with ferric iron, and form a distinct trend in oxygen isotopic composition. The conclusive evidence that SNC meteorites are from Mars is the analysis of gases trapped in glass inclusions in EETA79001, which chemically and isotopically match gases measured in the unique martian atmosphere by the Viking lander spacecraft (Figure 1).

    Martian Meteorites
    Name Classification Mass (kg) Find/Fall Year
    Shergotty S-basalt (pyx-plag) 4.00 fall 1865
    Zagami S-basalt 18.00 fall 1962
    EETA79001 S-basalt 7.90 find-A 1980
    QUE94201 S-basalt 0.012 find-A 1995
    ALHA77005 S-lherzolite (ol-pyx) 0.48 find-A 1978
    LEW88516 S-lherzolite 0.013 find-A 1991
    Y793605 S-lherzolite 0.018 find-A 1995
    Nakhla N-clinopyroxenite 40.00 fall 1911
    Lafayette N-clinopyroxenite 0.80 find 1931
    Gov. Valadares N-clinopyroxenite 0.16 find 1958
    Chassigny C-dunite (olivine) 4.00 fall 1815
    ALH84001 orthopyroxenite 1.90 find-A 1993
    Classificaion: S=shergottite, N=nakhlite, C=chassignite, ALH84001 is none of these.

    find-A designates Antarctic meteorites (all recent finds). Year is recovery date for non-Antarctic meteorites and date of martian classification for Antarctic meteorites.

    The martian meteorites represent five different types of igneous rocks, ranging from simple plagioclase-pyroxene basalts to almost monomineralic cumulates of pyroxene or olivine. The meteorites and their rock types are listed in Table 1. Photographs of whole rocks and thin sections of a basalt and a cumulate are illustrated below. All of the meteorites solidified near the martian surface by crystallization from a cooling magma. Some of the shergottite basalts have close to magma compositions, while the other martian meteorites are dominated by accumulation of olivine and/or pyroxene. None of the martian meteorites are surface samples in that they have not been exposed to extensive weathering or irradiation by cosmic rays. The martian soil analyzed by Viking appears to be a weathered basalt which could have been of shergottite composition.

    The only natural process capable of launching martian rocks to Earth is meteoroid impact. To be ejected from Mars a rock must reach the escape velocity of 5.4 km/sec, which is more than five times the muzzle velocity of a hunting rifle. During impact the kinetic energy of the incoming projectile causes shock deformation, heating, melting, and vaporization, as well as crater excavation and ejection of target material. The martian meteorites show low to moderate degrees of shock that appear to require a special mechanism to boost them to the escape velocity and eject them from Mars. The impact and shock provide an explanation for why the martian meteorites are all igneous rocks. Martian sedimentary rocks, and certainly soil, may not be sufficiently consolidated to survive the impact as intact rocks which might later land on Earth as meteorites.

    EETA79001, a basaltic shergottite, has light-colored xenoliths and dark glasses containing trapped martian atmosphere. ALHA77005 lherzolitic shergottite has a splotchy dark-light structure.
    ALH84001 orthopyroxenite has afractured zone where carbonate weathering products are more abundant. QUE94201 basaltic shergottite is tiny and the newest martian meteorite.

    Thin section of basaltic Shergottite shows melt texture of pyroxene and plagioclase mineral. Thin section of dunite Chassigny shows the cumulate texture of olivine in polarized light.

    Volcanism and Impact
    Water on Mars
    Martian Atmosphere
    Sample Return

    Last Update: 9 August 1996
    Source: Earth Science and Solar System Exploration Division, Johnson Space Center
    Responsible NASA Official: Eileen Stansbery (
    Web Curator: Anita Dodson