You would think if carbonaceous chondritic asteroids could make crystals
with 10-fold rotational symmetry, they could make something like RNA too?
http://physicsworld.com/cws/article/news/2012/aug/13/further-proof-of-extraterrestrial-origin-of-quasicrystalsFurther proof of extraterrestrial origin of quasicrystalsAn
international team of researchers has found nine new samples of naturallyoccurring quasicrystals. The work also provides further proof thatquasicrystals were delivered to
the Earth by a meteorite. The team'sdiscovery challenges our understanding of both crystallography andsolar-system formation.Conventional crystal structures are made of
atoms, or clusters of atoms,that repeat periodically. These patterns are normally restricted to two,three, four or sixfold rotational symmetry - the numbers corresponding
tohow many times the crystal appears the same during a rotation through 360°.For a long time these were considered hard and fast rules, and no crystalsthat broke these
conditions were thought to exist.Ordered, but not periodicHowever, Israeli physicist Daniel Shechtman found just such a rule-breakingcrystal in 1984 and was awarded the 2011
Nobel Prize for Chemistry for hisefforts. Shechtman had discovered a quasicrystal - a crystal that, whileordered, does not contain structures that repeat periodically.
Schectman'scrystal also had 10-fold rotational symmetry. Even after his discovery,there was a lot of scepticism about the existence of such a material. But asthe years went
by, other physicists began to construct quasicrystals oftheir own and now more than 100 different types have been found. These,however, are synthetic and have been created
under precisely controlledlaboratory conditions. Just as it was originally assumed that quasicrystalscould not exist, after their discovery it was assumed that they could
notexist naturally in the wider world.That assumption was called into question in 2009 when Princeton University'sPaul Steinhardt - the man who originally coined the term
"quasicrystal" -appeared to have discovered a naturally occurring variety in a rock samplefrom Russia. Steinhardt and his colleague Luca Bindi, from the University
ofFlorence, Italy, measured the ratio of oxygen isotopes within the sample andtheir results suggested that the rock belongs to a class of meteorites knownas carbonaceous
chondrites. Not only did this rock contain a naturallyoccurring quasicrystal, it also came from outer space.Thrilling pastBut the scepticism that had followed quasicrystals
around since theirdiscovery continued. The rock sample was traced back to Valery Kryachko, aRussian who in 1979 had been panning for platinum in a stream flowingthrough the
Koryak mountains in far-eastern Siberia. The rock had somehowturned up in Bindi's museum collection in Italy. "People were sceptical ofthe rock's back story as the tale
of how it got to Florence involves secretdiaries, smugglers and KGB agents," Steinhardt told physicsworld.com."The only way to settle the debate was to take a shot
at finding moresamples," Steinhardt explains. He put together a team of 10 scientists, twodrivers and one cook and set out on a four-day expedition across Siberiaback
to the stream where Kryachko had found the original sample. Once there,they panned 1.5 tonnes of sediment from the stream bank, eventuallyisolating a few kilograms for
analysis.After six weeks of painstaking grain-by-grain analysis, they hit onsomething special. "We found a grain with a fleck of metal on it. Not onlydid it contain
quasicrystals, but the oxygen-isotope ratio was exactly thesame [as the original sample]," says Steinhardt. "It was an incrediblemoment. Out in the field, no-one
bet on a more than 1% chance ofsuccessfully finding anything," he adds. The team isolated a total of ninequasicrystal samples. It is thought these samples all come from
the samemeteorite, and analysis of the sediment layers suggests it landed within thelast 15,000 years.Extreme formationAs the quasicrystals come from a
carbonaceous-chondrite meteorite, they musthave formed in the earliest days of the solar system. Carbonaceouschondrites are thought to have collided together to form the
cores of therocky planets, and so Steinhardt's quasicrystals are older than the Earthitself. However, current models cannot account for the presence of thesequasicrystals.
"We need a novel kind of geological process to form them andso it challenges our ideas of solar-system formation," Steinhardt says.The intense conditions present
in the solar system's youth also challengethe prevailing view of quasicrystals as objects that need a carefullycontrolled laboratory set-up to produce. "Quasicrystals
are not the delicatematerials previously thought. The ones we found must have been formed underrobust and hardy conditions in the early solar system," Steinhardt
says.Others agree that the world of quasicrystals could be changed by this10-fold increase in the number of known naturally occurring examples. "Thisresult emphasizes
how normal quasicrystals are and will hopefully make themless of an eccentricity," Renee Diehl, a surface physics researcher atPennsylvania State University, US, told
physicsworld.com. "It opens our eyesto the fact that they may have been all around us and we just have notnoticed," she explains.The research is published in
Reports on Progress in Physics.Phil WhitmerJoshua Tree Earth & Space Museum
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