The oldest volcanic rock we have ever discovered may help us understand the building blocks of planets. The meteorite, which was discovered in the Sahara desert in 2020, dates from just 2 million years after the formation of the solar system – making it more than a million years older than the previous record-holder.
“I have been working on meteorites for more than 20 years now, and this is possibly the most fantastic new meteorite I have ever seen,” says Jean-Alix Barrat at the University of Western Brittany in France. When he and his colleagues analysed the meteorite, called Erg Chech 002 or EC 002, they found that it was unlike any other meteorite we have ever located.
It is a type of rock called andesite that, on Earth, is found mostly in subduction zones – areas where tectonic plates have collided and one has been pushed beneath the other – and rarely in meteorites. Most of the meteorites discovered on Earth are made of another kind of volcanic rock called basalt. Analysis of the chemical make-up of the new meteorite showed that it was once molten, and solidified nearly 4.6 billion years ago.
This means it was probably part of the crust of an ancient protoplanet that broke up early in the solar system’s past. No known asteroid looks like EC 002, which indicates that almost none of these relics still exist: nearly all of them have either crashed together to form planets or been smashed to bits.
“When you go close to the beginning of the solar system, it’s more and more complicated to get samples,” says Barrat. “We probably will not find another sample older than this one.”
The researchers’ analysis showed that it took the magma that makes up EC 002 at least 100,000 years to cool and solidify after it melted, which may indicate that it was unusually viscous. Further study of this artefact from the early solar system could help us understand how the planets, including Earth, formed.
Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.2026129118
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