An unusual type of rock known as a quasicrystal was found deep in the Russian mountains in 2010. Now scientists think it may have come from outer space, and dates back to the earliest days of our solar system.
If you followed news of last year’s Nobel Prize in Chemistry, you heard about quasicrystals, an unusual type of material first described in the 1980s by Israeli scientist Daniel Schechtman. A quasicrystal has a strange atomic structure that gives it unique properties, falling somewhere between a true crystal and glass.
Schechtman found them quite by accident, while on sabbatical in the US. He was working with rapidly cooled alloys of aluminum and manganese, and noticed an unusual pattern in the electrondiffraction pattens they produced. Per this 2003 article in APS News:
“In normal crystals, atoms lie on three-dimensional lattices of cells. Each cell has an identical pattern of cells surrounding it. In a quasicrystal, he local arrangements of atoms are fixed, but each cell has a different configuration of cells nearby. Although the structures are strikingly similar to the quasiperiodic tilings invented by mathematician Roger Penrose … there was little in the crystallographic field to presace the experimental breakthrough.”
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Schechtman was famously ridiculed for his ideas when he first proposed them — he had great difficulty getting his discovery published in a peer-reviewed science journal for the first two years — but eventually it appeared in Physical Review Letters.
And in one of the best scientific underdog stories of recent memory, he proved correct, sparking a revolution in crystallography. That paper is now one of the ten most cited articles in the history of the journal. Today synthetic quasicrystals are used to strengthen steel or aluminum, or to create a coating with properties similar to Teflon.
People also speculated about naturally occurring quasicrystals, and finally geologists discovered just that while studying rocks in Russian’s Koryak mountains. But a new paper by Princeton University’s Paul Steinhardt, claims those naturally occurring quasicrystals have a far more exotic origin: they fell to Earth in meteorites from outer space.
Steinhardt and his team decided to start scanning databases of crystals in 1998 “to see if nature found ones that have not yet been discovered synthetically by trial and error,” according to Steinhardt. Using x-ray and electron diffraction imaging techniques, the scientists searched for any crystals that had patterns indicative of quasicrystals.
It took eight long years, but finally, in 2007, they sifted through a collection belonging to Luca Bindi of the University of Florence, which included a rock found in the Koryak Mountains. An alloy of aluminum, copper and iron, Its pattern clearly made it a quasicrystal.
A mass spectroscopy analysis of the Russian rock’s structure revealed unusual ratios of oxygen atoms and their isotopes, matching the ratios typically found inside a certain type of meteorite known as a carbonaceous chondrite. The samples also contained silica, suggesting it had formed under high pressure conditions.
Based on those findings, Steinhardt and his colleagues hypothesize that the most likely scenario is that the quasicrystal found in the Koryak Mountains fell to Earth inside a meteorite. Steinhardt announced his extraterrestrial origin theory in the Jan. 2 issue of the Proceedings of the National Academy of Science.
Far from being some rare, exotic new material, Steinhardt posits that, in fact, they could be one of the very first minerals that formed in the solar system, well before others more commonly found on Earth, and probably also exist in abundance through other galaxies as well.
“Now that we know that quasicrystals formed in the early solar system, we need to understand exactly how,” Steinhardt told the Christian Science Monitor. “More material and more tests are needed to understand how nature has managed to accomplish the feat.”
Image credit: Paul Steinhardt, Princeton University