[meteorite-list] Meteorite Quasicrystals

From: dorifry <dorifry_at_meteoritecentral.com>
Date: Tue, 3 Jan 2012 12:30:30 -0500
Message-ID: <504DF1340B2C4B85AD95470ECA867419_at_DoriPC>

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
Received on Tue 03 Jan 2012 12:30:30 PM PST