Odd Crystal Found From Outer Space --With A Structure Long Thought Impossible In Nature

 

 

Evidence has been found proving that the only known natural form of an odd type of crystal known as a quasicrystal originated in outer space. Like standard crystals, the atoms of a quasicrystal are ordered, but their arrangement lacks translational symmetry: a shifted copy won’t ever quite match its original.

Ever since their discovery in 1984, quasicrystals have posed a puzzle: “Why do the atoms form a complex, quasiperiodic pattern rather than a regularly-repeating, crystal arrangement?”

On the atomic scale, this pattern was long thought impossible, until the Nobel-prizewinning work of Daniel Shechtman of the Technion Israel Institute of Technology in Haifa, who was the first to spot an example in an alloy. When Shechtman first reported the atomic structure of a quasicrystal, it shocked researchers according to the journal Nature.

“Instead of a lattice of regularly repeating units like any normal crystal, the atoms were arrayed in a pattern that was ordered but never quite repeated itself, like an intricate three-dimensional mosaic. Around the time of the publication, Steinhardt, then at the University of Pennsylvania in Philadelphia, happened to be working with mathematician Dov Levine on the theory behind such non-repeating patterns. He later coined the term quasicrystal.”

But in 1979, a rock was dug up in the Koryak mountains -a remote gold-mining region- in north-eastern Russia with the same structure, which is now part of the collection of the Museum of Natural History in Florence, Italy. Except for this sample all other known quasicrystals had been synthesised in lab environments.

Last July theorectical physicist Paul Steinhardt of Princeton University, who wrote a seminal paper –A New Paradigm for the Structure of Quasicrystals–led a team across the Russian tundra into the Koryak mountains to search for the original source of the quasicrystal now housed in the Florence museum.

 

 

“I just grabbed the problem and held on wherever it dragged me — even across the tundra,” said Steinhardt, from Princeton University in an interview with Nature. The story seemed likesomething out of an Indiana Jones thriller, including secret diaries, smuggling and the discovery that nature’s quasicrystal appears to have come from a meteorite some 4.5 billion years old that fell to Earth around 15,000 years ago, making the quasicrystal one of the oldest minerals in existence, formed at the birth of the Solar System. Steinhardt’s finding was published in the Proceedings of the National Academy of Sciences.

Earlier, in autumn of 2008 Steinhardt was contacted by Luca Bindi, a mineralogist at the Museum of Natural History in Florence, Italy, who had found a quasicrystal grain, around 100 micrometres across, in a millimetre-sized rock fragment in the museum’s collection.

In 2009, Steinhardt, Bindi and their colleagues reported in Science that the grain was a quasicrystalline alloy of aluminium, copper and iron. According to the label on the box in which it was stored, the rock came from the Koryak Mountains in Russia.

In the latest study, Bindi joined with Steinhardt and other US scientists to analyze the chunck of metorite. The ratios of isotopes of oxygen in silicate and oxide minerals around the quasicrystal grain are typical of minerals found in meteorites called carbonaceous chondrites, which indicated that the rock is of extraterrestrial origin and very old: virtually all chondrites formed at the birth of the Solar System, whereas the bulk of minerals that we know on Earth today did not start to form until plate tectonics and the oxygenation of the atmosphere created new kinds of physical and chemical environments. Only around a hundred minerals have the distinction of forming before that, reported Nature, when matter started colliding and coalescing to form the Solar System.

Image at top of page is an Alpha Monocerotid meteor shower.

The Daily Galaxy via:

http://www.nature.com/news/the-quasicrystal-from-outer-space-1.9728http://www.physics.princeton.edu/~steinh/quasi/