Scientists excavate meteorite from the birth of the solar system

Scientists believe they have identified a meteorite that formed in the first million years of our solar system, making it the oldest known meteor of volcanic origin.

The space rock, which began its journey some 4.5 billion years ago, has already proved an “exceptional” witness to the building blocks of the planets.

Known as Erg Chech 002, the meteorite was discovered in May 2020 by meteor hunters in the Algerian Sahara. According to Jean-Alix Barrat, a geochemist at the French University of Brest, it had lain undisturbed for “at least 100 years”.

In a recent study published in the Proceedings of the National Academy of Sciences diary, Barrat and his colleagues describe its discovery and several rare features.

There are 43 officially documented fragments, but “probably about a hundred”, either still in the ground or missing, the study said. The largest are “the size of a fist,” Barrat told AFP.

With its greenish exterior and brownish interior, Erg Chech 002 may not seem extraordinary at first glance. But it is, in fact, extremely rare.

Of the approximately 65,000 meteorites so far documented on Earth, only about 4,000 contain what is known as “differentiated matter.” This means that they came from celestial bodies large enough to have experienced tectonic activity.

Of those 4,000, 95 percent comes from just two asteroids. But Erg Chech 002 is among the remaining five percent.

“It is the only one of the 65,000 meteorites that is what it is,” said Barrat.

“Such rocks were common in the early solar system history.”

There are two possible explanations for the rarity of Erg Chech 002.

The type of protoplanet from which it originated provided raw material “for the growth of terrestrial planets,” such as Earth, Barrat said.

Others were pulverized in the great cosmic billiards game of the formation of the solar system.

The moon’s surface, pockmarked with countless asteroid impacts, is a relatively recent witness to this second type of protoplanet.

“No asteroid shares the spectral features of EC 002, indicating that almost all of these bodies have disappeared, either because they became the building blocks of larger bodies or planets, or were simply destroyed,” the study said.

‘Thrown into Space’

The so-called “parent body” of Erg Chech 002 could have measured a diameter of about 100 kilometers.

It was formed in the first million years of the solar system, according to the study’s co-authors, March Chaussidon, of the Paris Globe Institute of Physics and Johan Villeneuve, a researcher at the French National Center for Scientific Research at the University of Lorraine. .

Metallic meteorites “correspond to the nuclei of protoplanets,” Barrat said.

But Erg Chech 002 is of volcanic origin, meaning it was part of a protoplanet’s crust, rather than its core.

The experts believe that the unique composition was the result of a series of happy events.

On the protoplanet in question, lava must have accumulated on its surface, fueled by the heat of its aluminum core.

The meteorite crust solidified for a moment, but – as it showed signs of a sudden cooling – instead of staying on the mother’s body, some violent force scattered it.

“The rock was thrown into space,” Barrat said.

Further investigation of the composition revealed that Erg Chech 002 was formed about 4.65 billion years ago.

It traveled through the eons, “in a gravel enclosure, protected from solar radiation,” Barrat said.

Then, about 26 million years ago, the rock was dislodged and continued on its journey until it collided with the earth.

© 2021 AFP