What are quasicrystals discovered in a micrometeorite and why are they an "impossible" material

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What are quasicrystals discovered in a micrometeorite and why are they an "impossible" material
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A quasicrystal was identified in a tiny meteorite recovered in 2002 in Calabria, a material so exceptional that it was defined as “impossible”. Here's what quasicrystals are and why they make the small space rock that crashed in Italy one of the rarest in the world.

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The micrometeorite in which the quasicrystal was detected. Credit: Communications Earth & Environment

At the heart of a tiny meteorite recovered in 2002 on the top of Mount Gariglione , Calabria , scientists made an extraordinary discovery. Inside, thanks to in-depth laboratory analyses, they have in fact identified a quasicrystal , a solid material with ” impossible ” characteristics. Before delving into the explanation of what makes quasicrystals so special, it is necessary to underline the exceptional nature of the all-Italian discovery . Suffice it to say that the presence of the quasicrystal makes the scoriaceous micrometeorite of just 500 micrometers (classified under the name FB-A1 ) one of the rarest meteorites in the world . Yes, because quasicrystals had only been identified in one other meteorite (the Khatyrka meteorite ), furthermore this is the third detection ever in a body of extraterrestrial origin . It is no coincidence that the results of the investigations on the tiny spherule, found about sixty kilometers from Catanzaro, quickly hit the pages of scientific institutions around the world.

The quasicrystal was discovered in the FB-A1 micrometeorite by an all-Italian research team led by scientists from the Department of Earth and Geoenvironmental Sciences of the University of Bari Aldo Moro and the Department of Earth Sciences of the University of Florence, who collaborated closely with colleagues from the Italian Space Agency – Matera Space Center and the MEMA Service Center of the University of Florence. The researchers, coordinated by Mineralogy teachers Giovanna Agrosì and Luca Bindi , subjected the tiny fragment to non-destructive analyzes – therefore on the intact sample – such as computerized X-ray microtomography (μ-CT) and scanning electron microscopy (SEM) with a peculiar spectrometer. Tests revealed that the shiny spherule contained an icosahedral quasicrystal with an unusual composition: Al 51.7 Cu 30.8 Fe 10.3 Si 7.2 .

In simple words, it is an anomalous metal alloy containing Aluminium, Copper, Iron and Silicon. A similar quasicrystal was also found in the Khatyrka meteorite, recovered from the river of the same name during an expedition in Chukotka, in far eastern Russia. It is important to underline that this extraordinary discovery would not have been possible without the intuition of a so-called “citizen scientist”, a micrometeorite enthusiast who collected the spherule on the Calabrian mountain. Surprised by its shine characteristics, he decided to send it to the University of Bari, where the research that led to the incredible results reported here began.

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What are quasicrystals

So, what are these quasicrystals? In essence, these are solid materials in which the atoms are arranged with ordered but not periodic/repetitive symmetries . This characteristic makes them impossible – or rather, forbidden (forbidden) – for classical crystallography . In other words, quasicrystals have an exotic structure that defies the structural rules of a typical crystal. “Quasicrystals are materials in which the atoms are arranged as in a mosaic, in regular patterns but which never repeat in the same way, unlike what happens in ordinary crystals,” explained Professor Bindi in a press release from University of Bari. It is not surprising that the first to discover quasicrystals, the Israeli researcher Dan Shechtman of the Technion – Israel Institute of Technology during experiments conducted in the early 1980s, had quite a few problems getting his “eureka” accepted. Then, fortunately, the scientific community appreciated his work so much that it awarded him the Nobel Prize for Chemistry in 2011.

The atomic distribution of a quasicrystal. Credit: J.W. Evans

The atomic distribution of a quasicrystal. Credit: JW Evans

The quasi-crystalline state is normally obtained artificially (synthesized) in the laboratory by mixing the elements desired by researchers. It was precisely while trying to obtain a particular metallic alloy that Professor Shechtman noticed quasicrystals for the first time. These materials possess peculiar properties – such as hardness and low thermal conductivity – which makes them excellent for developing coatings and certain technologies that must last over time.

It was Professor Bindi who discovered the first natural quasicrystal, inside the Khatyrka meteorite in 2009. To date, thanks to the micrometeorite found in Calabria, we have only three pieces of evidence of this extraordinary material in nature, specifically extraterrestrial material. “The discovery is very important not only for mineralogical and planetary sciences but also for solid state physics and chemistry; it demonstrates once again that quasicrystals can form spontaneously in nature and, above all, remain stable for geological times”, declared Professor Giuseppe Mastronuzzi, Director of the Department of Earth and Geoenvironmental Sciences of the University of Bari.

The discovery is also a source of pride for space scientific research in Southern Italy: “The development of Planetary Sciences in Southern Italy is a point in which we have always believed and this discovery demonstrates how the contribution of geological-mineralogical studies is essential for the progress of knowledge about our Solar System”, highlighted Professor Giovanna Agrosì. As explained by Dr. Paola Manzari of the Research and Higher Education Coordination Unit (UCR) of the Matera Space Center of the ASI, in fact, “the discovery of this anomalous alloy in a chondritic matrix together with the presence of quasicrystals opens up new scenarios on origins of the original material from which the fragment broke off and provides new elements for understanding the mechanisms of formation of the Solar System”. The details of the research “A naturally occurring Al-Cu-Fe-Si quasicrystal in a micrometeorite from southern Italy” were published in the scientific journal Communications Earth & Environment of the Nature circuit.

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