10 August 2012
Evidence is mounting that the only known natural form of a bizarre type of crystal known as a quasicrystal originated in 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.
Such a pattern on the atomic scale 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.
Since then, the strange arrangement has also been discovered in a rock dug up in the Koryak mountains in eastern Russia in 1979, which is now part of the collection of the Museum of Natural History in Florence, Italy. Except for this sample, though, all other known quasicrystals had been synthesised in lab environments.
Last July a team of scientists led by Paul Steinhardt of Princeton University trekked across the tundra into the Koryak mountains on a quest to find the source of the naturally occurring quasicrystal. Based on the conditions required for the natural formation of quasicrystals, the team reported on their return evidence that the quasicrystal must have fallen from space.
Now Steinhardt and Bindi report that the 2011 expedition turned up further naturally occurring samples of quasicrystal (pictured above). And the samples back up their previous claim that the quasicrystals come from a 4.5-billion-year-old meteorite that fell to Earth around 15,000 years ago.
Space chemistry 1: Earth-based nature 0.
What’s more, Steinhardt says that the newly found grains are in better condition than the samples that lie in Florence:
“Whereas the Florence sample had been pulverized early on and, except for a few micrograins, destroyed and all context lost, here we have a full grain.”
His team is now analysing the new samples to see what they might reveal about quasicrystals – and the state of the early solar system.