PRIZE

Martian Meteorite - NWA 2975

 

View entire thin section of NWA 2975

Rotation views of NWA 2975

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Transmitted light
plane polarisedhttp://www.open.ac.uk/earth-research/tindle/AGT/mosaics/zgoogle_nwa2975ppl/index.html
Transmitted light
between crossed polarshttp://www.open.ac.uk/earth-research/tindle/AGT/mosaics/zgoogle_nwa2975xpl/index.html
Reflected lighthttp://www.open.ac.uk/earth-research/tindle/AGT/mosaics/zgoogle_nwa2975ref/index.html
Rotation point 1Mars-NWA-2975-rotate1.html
Rotation point 2Mars-NWA-2975-rotate2.html

10 mm

Africa

Morocco






Algeria

The first specimen of this basaltic shergotitte (achondrite) was purchased in Erfoud, Morocco (in 2005), but the strewn field is thought to be in Algeria. There may be over 100 pieces, estimated to total 1.6 kg. Many have a fresh fusion crust (partial), a basaltic texture and distinctive black glass pockets and veins. Our sample has a small area of fusion crust and is still encrusted with desert sand.


NWA 2975 is medium-grained and consists of pale green prismatic pyroxene (augite and pigeonite) intergrown with white/colourless plagioclase feldspar that has been entirely converted to maskelynite due to shock metamorphism. Minor constituents include the phosphate merrillite and three opaque species (ilmenite, pyrrhotite and ulvospinel). The Mn/Fe ratio of the pyroxene is comparable to other samples of Martian origin.


NWA 2975 is a paired sample - indicating that there are other samples that are thought to be derived from the same meteorite shower. These include NWA 2986, 2987, 4766, 4783, 4857, 4864, 4878, 4880, 4930, 5140, 5214, 5219 and 5366.


This description is based on the work of NASA scientist Charles Meyer - compiler of The Mars Meteorite Compendium, and scientists from the universities of Northern Arizona and Washington.


The rarity of NWA 2975 can be gauged by its value - one 102 gm sample is on sale for $100,000 (click here). The piece illustrated above was offered as a prize to readers of New Scientist (click here).

Many thanks to Ted Bunch of the Northern Arizona University for permission to use the NWA 2975 thin section. Note that rounded crystals of (mainly) quartz surround the sample - put there to help with sample preparation.

Hand specimen and thin section photographs are courtesy of the Open University Virtual Microscope team.