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Diamonds recovered successful 4 meteorites successful north-west Africa astir apt came from an past dwarf planet, and they are expected to beryllium harder than Earth diamonds
Space 12 September 2022By Alice Klein
Electron microscopy has revealed hexagonal diamonds (the acheronian country adjacent the mediate of the picture) successful meteorites recovered successful Africa Alan Salek/RMIT
Mysterious hexagonal diamonds that don’t hap people connected Earth person been discovered successful 4 meteorites successful north-west Africa.
“It’s truly breathtaking due to the fact that determination were immoderate radical successful the tract who doubted whether this worldly adjacent existed,” says Alan Salek astatine RMIT University successful Melbourne, Australia, who was portion of the squad that recovered them.
Hexagonal diamonds, similar regular diamonds, are made of carbon, but their atoms are arranged successful a hexagonal operation alternatively than a cubic one.
Also known arsenic lonsdaleite, hexagonal diamonds were archetypal reported successful meteorites successful the US and India successful the 1960s. However, the antecedently discovered crystals were truthful tiny – lone nanometres successful size – that it was hard to corroborate whether they were genuinely hexagonal diamonds.
To hunt for larger crystals, Salek and his colleagues utilized a almighty electron microscope to adjacent into 18 meteorite samples. One was from Australia and the remainder were from north-west Africa.
They recovered hexagonal diamonds successful 4 of the African meteorites, with immoderate crystals measuring up to a micrometre successful size – astir 1000 times bigger than erstwhile discoveries. This allowed the squad to corroborate the antithetic hexagonal structure.
“It’s an important find due to the fact that present we person larger crystals, we tin get a amended thought of however they formed and possibly replicate that process successful the lab,” says Salek.
Based connected the chemic creation of the meteorites that brought them to Earth, the hexagonal diamonds look to person formed wrong dwarf planets, says Andy Tomkins astatine Monash University successful Melbourne, who led the research.
The team’s investigation suggests the crystals were created by a absorption betwixt graphite – which is made of c atoms layered successful sheets – and a supercritical fluid of hydrogen, methane, oxygen and sulphur chemicals that astir apt formed erstwhile an asteroid crashed into the dwarf satellite and broke it into fragments that yet fell onto Earth.
“When the satellite broke apart, it was similar taking a lid disconnected a Coke vessel – it released the unit and that driblet successful unit combined with precocious temperatures led to the merchandise of this supercritical fluid,” says Tomkins.
This is akin to the process by which regular diamonds are made successful labs, by heating graphite with gases similar hydrogen and methane, suggesting that a fewer tweaks could nutrient lonsdaleite instead, says Salek.
Hexagonal diamonds are predicted to beryllium astir 60 per cent harder than regular diamonds based connected their structure, and this other hardness could person important concern applications if they could beryllium made synthetically. For example, they could perchance beryllium utilized to marque ultra-hard saw blades oregon different instrumentality parts, says Salek.
Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.2208814119
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