Antarctic meteorite ALH84001 is a member of twelve martian meteorites that are widely believed to have originated on planet Mars based upon several lines of evidence. ALH84001 is an ancient orthopyroxenite rock of 4.5 billion years old that contains abundant Ca–Fe–Mg carbonates, unlike other martian meteorites. Recently, it has been reported that ALH84001 contains (1) unique mineral compositions and biominerals, (2) polycyclic aromatic hydrocarbons (PAHs) in association with carbonates, and (3) unique structures and morphologies typical of nannobacteria or microfossils. They are interpreted as a possible relic biogenic activity on early Mars. We review the possibility of alternative explanations for these phenomena, especially for mineralogical features in the carbonate globules. Although it may be possible to consider that such phenomena in carbonates are biogenic rather than inorganic in origin, we show more difficulty in the biogenic interpretation than has been discussed. Because it is very difficult to conclude that they are biogenic or non-bio-genic from present data, it is necessary to further study ALH84001 and other martian meteorites. We also need to consider future Mars missions, especially sample return missions. In this consequence, we should start to think about a curation system and analytical facilities in Japan in cooperation with other related communities.

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Twelve martian meteorites are well known so far as SNC meteorites (Shergottites (S), Nakhlites (N) and Chassignites (C)), which are belevied to have originated from Mars. All the martian meteorites are igneous rocks formed by crystallization of a magma on the parent planet, Mars, during recent history of the solar system (116 Ma∼1.3 Ga) except one specimen. Most martian meteorites show a typical crystalline igneous texture with intense shock, and only two specimens (ALH84001 and Yamato-793605) show the monomict brecciaed texture. Especially, ALH84001 is orthopyroxene monomict breccia indicating a remarkably old age of 4.5 Ga, and suggest the past life on Mars.
According to their textures, martian meteorites are briefly separated into two textural groups: crystalline and breccia. A crystalline group includes cumulate, poikilitic and gabbroic-basaltic textures. They are preliminary classified into five rock types of dunite, lherzolite, wehrlite, gabbro-dolerite and orthopyroxenite from texture, mineral assemblages and chemical compsitions.
Author presents general view of twelve martian meteorites and brief describes their textures, mineral assemblages and chemical compositions along with their crystallization.

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Alkali feldspar grains in a quartz syenite from Cape Ashizuri, southwest Japan, consist of two parts: clear and turbid. The rims of grains are turbid and show lamellar textures of microperthites. Both clear and turbid parts are scattered irregularly inside grains. The clear parts are optically featureless and cryptoperthitic. The inner turbid parts are mosaic and lamellar microperthites. In some sections, only lamellar microperthites are developed throughout a grain. Calcium distribution maps were obtained for feldspar grains showing the above textures. The rims are always poor in calcium (nearly 0 mol% An). The inner clear parts are generally rich in calcium (5 mol% An at the maximum) around the composition of about Or₃₃Ab₆₄An₃, but in some cases poor in calcium (-0.1mol% An). The sodium-rich phase of the microperthite of the inner turbid parts are variable in calcium content from 7 to nearly 0 mol% An. On the other hand, the potassium-rich phase of the microperthite is always poor in calcium both in the rims and inside the grains. The total calcium distribution patterns suggest a possible calcium transfer from the inside to the outside of grains under hydrother-mal conditions with microperthite formation.

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