[meteorite-list] Meteorite Quasicrystals

[dorifry]

http://www.newscientist.com/article/dn21325-nobel-prizewinning-quasicrystal-gets-alien-status.html

A Nobel prizewinning crystal has just got alien status. It now seems that 
the only known sample of a naturally occurring quasicrystal fell from space, 
changing our understanding of the conditions needed for these curious 
structures to form.

Quasicrystals are orderly, like conventional crystals, but have a more 
complex form of symmetry. Patterns echoing this symmetry have been used in 
art for centuries but materials with this kind of order on the atomic scale 
were not discovered until the 1980s.

Their discovery, in a lab-made material composed of metallic elements 
including aluminium and manganese, garnered Daniel Shechtman of the Technion 
Israel Institute of Technology in Haifa last year's Nobel prize in 
chemistry.

Now Paul Steinhardt of Princeton University and colleagues have evidence 
that the only known naturally occurring quasicrystal sample, found in a rock 
from the Koryak mountains in eastern Russia, is part of a meteorite.

Nutty conditions
Steinhardt suspected the rock might be a meteorite when a team that he led 
discovered the natural quasicrystal sample in 2009. But other researchers, 
including meteorite expert Glenn MacPherson of the Smithsonian Institution 
of Washington DC, were sceptical.

Now Steinhardt and members of the 2009 team have joined forces with 
MacPherson to perform a new analysis of the rock, uncovering evidence that 
has finally convinced MacPherson.

In a paper that the pair and their teams wrote together, the researchers say 
the rock has experienced the extreme pressures and temperatures typical of 
the high-speed collisions that produce meteoroids in the asteroid belt. In 
addition, the relative abundances of different oxygen isotopes in the rock 
matched those of other meteorites rather than the isotope levels of rocks 
from Earth.

It is still not clear exactly how quasicrystals form in nature. Laboratory 
specimens are made by depositing metallic vapour of a carefully controlled 
composition in a vacuum chamber. The new discovery that that they can form 
in space too, where the environment is more variable, suggests the crystals 
can be produced in a wider variety of conditions. "Nature managed to do it 
under conditions we would have thought completely nuts," says Steinhardt.

Journal reference: Proceedings of the National Academy of Sciences, DOI: 
10.1073/pnas.1111115109

http://www.livescience.com/17708-bizarre-crystal-meteorite.html

http://www.nature.com/news/the-quasicrystal-from-outer-space-1.9728

Phil Whitmer

Joshua Tree Earth & Space Museum