Scientists discover part of protoplanet older than Earth in Sahara desert
A sample of the meteorite EC 002 / the Sahara desert. Image: Maine Mineral and Gem Museum / Darryl Pitt (left) / DEA / C. SAPPA Contributor via Getty Images (right)
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In the spring of 2020, an incredible relic was discovered in a remote region of the Sahara Desert: an ultra-rare piece of an embryonic planet that existed before Earth was born.
Known as Erg Chech 002 (EC 002), the meteorite was forged from the crust of an ancient protoplanet, a small celestial body that serves as the building block of the planets. The volcanic space rock is “the oldest known lava” to ever fall to Earth and offers unprecedented glimpse into planetary formation at the start of the solar system, according to a study released Monday in Proceedings of the National Academy of Sciences.
Scientists led by Jean-Alix Barrat, professor of geochemistry at the University of Western Brittany in France, jumped at the opportunity to examine this extraordinary time capsule from the childhood of the solar system, which belongs to the andesitic family of volcanic rocks and is unlike anything that has been seen before.
“When we saw the first descriptions of this rock it was really obvious that this rock was unusual,” Barrat said in an email. Based on his previous research on another rare andesitic meteorite, described in a 2014 study, Barrat and his colleagues also knew that EC 002 was potentially very old.
“Age was not the only point of interest,” he noted. “We were extremely interested in the genesis of these extraterrestrial andesitic melts and the processes of primordial scab formation. Such samples are extremely valuable.
Named after its landing site in the sea of Erg Chech dunes in Algeria, EC 002 consists of several meteorites that collectively weigh around 70 pounds. The stones, which contain stunning crystals, were found in May 2020, but terrestrial erosion of alien rocks suggests they fell into the desert much earlier.
“It’s not a freshly fallen meteorite,” Barrat confirmed. “It is slightly altered, but we know since the study of the Tatahouine meteorite that terrestrial alteration is rapid even in the Sahara.
After obtaining samples of the meteorite, Barrat and his colleagues were able to determine when this piece of protoplanetary crust, which had partially melted as lava, crystallized into a solid form.
Analysis of the isotopes of magnesium and aluminum in the rock revealed that it dates back around 4.566 billion years, making it “the oldest known piece of igneous crust” ever found, the study reports. . For comparison, the next oldest igneous meteorite, called NWA 11119, is about 1.24 million years younger than EC 002, while the Earth itself began to emerge several million years after the formation of these rocks.
In addition to its unrivaled age, EC 002 also stands out for its unusual composition. The meteorite contains 58% silicon dioxide, a telltale sign that its former parent body had a crust made of andesite rock, which is distinct from basalt, a more familiar igneous material that is common in active volcanic regions of Earth.
Barrat and his colleagues note that these andesitic crusts were likely abundant in asteroids and protoplanets at the start of the solar system, but have become extremely rare over the billions of years since this bygone era. Ancient protoplanets were either incorporated into larger bodies such as the Earth or destroyed by collisions with other rocks during the tumultuous and collision-prone period of our solar system.
“EC 002 is clearly distinguishable from all asteroid groups, and no object with spectral characteristics similar to EC 002 has been identified to date,” the team in the study said, adding that the remains of Primal crusts are “not only rare in the meteorite record, but they are also rare today in the asteroid belt.
“This suggests that the first differentiated protoplanets that populated the solar system, as well as most of their debris, were likely destroyed or subsequently accreted to growing rocky planets, making the discovery of meteorites from primordial crusts an event. exceptional “, the researchers noted.
The team believes that EC 002 was ejected from its parent body by one of these encounters just decades after the protoplanet’s crust cooled and crystallized, revealing amazing new details about the evolution of planetary embryos. before the existence of Earth.
Barrat said he and his colleagues, along with other teams, were working to confirm the age of EC 002 with other isotopic studies. The researchers also want to study the crystals inside the rock, which are older than the surrounding volcanic material.
“If we know the compositions of the magmas produced at the start of a protoplanet’s magmatic activity,” he concluded, “we can deduce a lot of things about the construction of its crust.
Update: This article has been updated to include comments from study leader Jean-Alix Barrat.