Introduction to Meteorics
Lunar meteorites: there are currently 31 known lunar meteorites (not accounting for paired samples),
15 of which have been collected in Antarctica. Several are gabbroic or basaltic in nature, but the majority are anorthositic regolith breccias. An example of a lunar meteorite is Dar al Gani 262.
there are currently 37 meteorites that almost certainly originate on Mars (not accounting for paired samples). The martian origin rests on the age, composition and noble gas inventory of the meteorites (brief review
). The meteorites are all igneous in nature, and can be sub-divided into 4 groups:
- Shergottites (after Shergotty) are pyroxene-plagioclase rocks that are further sub-divided into basaltic and lherzolitic types.
- Nakhlites (after Nakhla) are shallow cumulates that have been exposed to the martian hydrosphere, and thus contain rich assemblages of carbonates, sulphates and halite.
- Chassigny, the only example of its type, is an olivine rich, dunite.
- Allan Hills (ALH) 84001, like Chassigny, is the only one of its type. It is an orthopyroxenite rich in carbonates. Since recognition of microstructures within the carbonates,
which were interpreted to be fossilised martian bacteria (McKay et al., 1996), ALH 84001 has been the focus of more attention (scientific and media) than any other meteorite.