Nakhlites
The Martian meteorites of this group are named for Nakhla, a fall that
occurred in El Nakhla, Egypt, in 1911. The nakhlites are clinopyroxenites,
displaying a sugary, fine-grained texture. They consist primarily of green
cumulate augite crystals with minor olivine in a very fine-grained
mesostasis.This mesostasis is composed of plagioclase, alkali feldspar,
pyroxenes, iron-titanium oxides, sulfides and phosphates. Traces of
pre-terrestrial aqueous alteration products are present in the form of
hydrated minerals, e.g. amphibole, clay minerals similar to iddingsite or
smectite, and carbonate and sulfate salts. Some researchers have proposed that
the presence of these hydrated minerals in the nakhlites, in addition to
concentrations of water-soluble ions such as Cl, K, Na, and Ca, suggests that
they resided in an environment in which liquid seawater was present for some
time, perhaps inside of an ancient Martian ocean.
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