When this uniquely beautiful meteorite surfaced in the Sahara last year, I jumped on it, buying the 1,857g stone before the isotope analyses confirmed that it was a meteorite at all. It was an enigmatic mystery, looking unlike any meteorite I had ever seen. Michael Farmer agreed, and when we sliced it in half, we found a treasure trove of green crystals (some 4cm long!) that must have formed in a planetary-sized body with very slow cooling of the crust over 100,000+ years. But which? Given the Earth-like preponderance of silicon dioxide crystals (58% by volume), some speculated that it might be the first meteorite knocked loose from the Earth itself, an emissary from its early formation.
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But we now know it’s older still. It is an ancient survivor from the crust of a lost cousin planet that formed 23 million years before Earth itself! EC 002 was all over the science news this week, with some of the articles featuring photos of my stones. What a beautiful birthday-week surprise! (and here are all of my photos)
From New Scientist: 4.6-billion-year-old meteorite is the oldest volcanic rock ever found
“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.”
LiveScience added: 4.6-billion-year-old meteorite belongs to Earth’s long-lost baby cousin
“When the scientists peered at distant cosmic objects’ spectral “fingerprints” — wavelength patterns in the light they emit or reflect — and compared them to EC 002, they found no matches. Even after comparison with 10,000 objects in the Sloan Digital Sky Survey database, EC 002 was “clearly distinguishable from all asteroid groups,” the scientists reported. “No object with spectral characteristics similar to EC 002 has been identified to date.”
Where are all the protoplanets with andesite crusts today? During our solar system’s volatile period of planetary birth, most of these protoplanets likely didn’t make it past infancy, according to the study. Either they were smashed to bits in collisions with other rocky bodies, or they were absorbed by bigger and more successful rocky planets, such as Earth, Mars, Venus and Mercury, leaving few traces behind to spawn meteorites such as EC 002.
“Remains of primordial andesitic crust are therefore not only rare in the meteorite record, but they are also rare today in the asteroid belt,” the scientists wrote.”
And here is the original paper in the Proceedings of the National Academy of Sciences: A 4,565-My-old andesite from an extinct chondritic protoplanet
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