Let me try that again:
http://physicsworld.com/cws/article/news/2012/aug/13/further-proof-of-extraterrestrial-origin-of-quasicrystals
Phil Whitmer
----- Original Message -----
From: "dorifry" <[email protected]>
To: "meteorite central" <[email protected]>
Sent: Tuesday, August 14, 2012 10:58 AM
Subject: [meteorite-list] Meteoritic Quasicrystals: Secret Diaries,Smugglers
and KGB Agents; Oh My!
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-quasicrystalsFurtherproof of extraterrestrial origin of quasicrystalsAn
international team ofresearchers has found nine new samples of naturallyoccurring quasicrystals.The work also provides further proof thatquasicrystals were delivered to
theEarth by a meteorite. The team'sdiscovery challenges our understanding ofboth crystallography andsolar-system formation.Conventional crystalstructures are made of atoms,
or clusters of atoms,that repeat periodically.These patterns are normally restricted to two,three, four or sixfoldrotational symmetry - the numbers corresponding tohow many
times the crystalappears the same during a rotation through 360°.For a long time these wereconsidered hard and fast rules, and no crystalsthat broke these conditionswere
thought to exist.Ordered, but not periodicHowever, Israeli physicistDaniel Shechtman found just such a rule-breakingcrystal in 1984 and wasawarded the 2011 Nobel Prize for
Chemistry for hisefforts. Shechtman haddiscovered a quasicrystal - a crystal that, whileordered, does not containstructures that repeat periodically. Schectman'scrystal also
had 10-foldrotational symmetry. Even after his discovery,there was a lot of scepticismabout the existence of such a material. But asthe years went by, otherphysicists began
to construct quasicrystals oftheir own and now more than100 different types have been found. These,however, are synthetic and havebeen created under precisely
controlledlaboratory conditions. Just as it wasoriginally assumed that quasicrystalscould not exist, after their discoveryit was assumed that they could notexist naturally
in the wider world.Thatassumption was called into question in 2009 when Princeton University'sPaulSteinhardt - the man who originally coined the term
"quasicrystal" -appearedto have discovered a naturally occurring variety in a rock samplefromRussia. Steinhardt and his colleague Luca Bindi, from the
UniversityofFlorence, Italy, measured the ratio of oxygen isotopes within the sampleandtheir results suggested that the rock belongs to a class of meteoritesknownas
carbonaceous chondrites. Not only did this rock contain anaturallyoccurring quasicrystal, it also came from outer space.ThrillingpastBut the scepticism that had followed
quasicrystals around sincetheirdiscovery continued. The rock sample was traced back to ValeryKryachko, aRussian who in 1979 had been panning for platinum in a
streamflowingthrough the Koryak mountains in far-eastern Siberia. The rock hadsomehowturned up in Bindi's museum collection in Italy. "People weresceptical ofthe rock's
back story as the tale of how it got to Florenceinvolves secretdiaries, smugglers and KGB agents," Steinhardt toldphysicsworld.com."The only way to settle the
debate was to take a shot atfinding moresamples," Steinhardt explains. He put together a team of 10scientists, twodrivers and one cook and set out on a four-day
expeditionacross Siberiaback to the stream where Kryachko had found the originalsample. Once there,they panned 1.5 tonnes of sediment from the stream
bank,eventuallyisolating a few kilograms for analysis.After six weeks ofpainstaking grain-by-grain analysis, they hit onsomething special. "We founda 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 beton a more than 1% chance ofsuccessfully finding anything," he adds. The teamisolated a total of ninequasicrystal samples.
It is thought these samplesall come from the samemeteorite, and analysis of the sediment layerssuggests it landed within thelast 15,000 years.Extreme formationAs
thequasicrystals come from a carbonaceous-chondrite meteorite, they musthaveformed in the earliest days of the solar system. Carbonaceouschondrites arethought to have
collided together to form the cores of therocky planets, andso Steinhardt's quasicrystals are older than the Earthitself. However,current models cannot account for the
presence of thesequasicrystals. "Weneed a novel kind of geological process to form them andso it challenges ourideas of solar-system formation," Steinhardt
says.The intense conditionspresent in the solar system's youth also challengethe prevailing view ofquasicrystals as objects that need a carefullycontrolled laboratory
set-upto produce. "Quasicrystals are not the delicatematerials previously thought.The ones we found must have been formed underrobust and hardy conditions inthe early
solar system," Steinhardt says.Others agree that the world ofquasicrystals could be changed by this10-fold increase in the number ofknown naturally occurring examples.
"Thisresult emphasizes how normalquasicrystals 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 havebeen all around us and we just have notnoticed," she explains.The
researchis published in Reports on Progress in Physics.Phil WhitmerJoshua Tree Earth& Space Museum______________________________________________Visit the Archives
athttp://www.meteoritecentral.com/mailing-list-archives.htmlMeteorite-list mailing
[email protected]http://six.pairlist.net/mailman/listinfo/meteorite-list
______________________________________________
Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html
Meteorite-list mailing list
[email protected]
http://six.pairlist.net/mailman/listinfo/meteorite-list
