In the spring of 2020, an amazing relic was discovered in a remote region of the Sahara desert: an ultra-rare chunk of an embryonic planet that existed before Earth was born.
Known as Erg Chech 002 (EC 002), the meteorite was forged within the crust of an ancient protoplanet, a small celestial body that serves as a building block for planets. The volcanic space rock is “the oldest known lava” that has ever fallen to Earth and offers an unprecedented glimpse of planetary formation in the early solar system, according to a study published on Monday in Proceedings of the National Academy of Sciences.
Scientists led by Jean-Alix Barrat, a professor of geochemistry at the University of Western Brittany in France, jumped at the opportunity to examine this extraordinary time capsule from the infancy of the solar system, which is unlike anything that has been seen before.
“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 said in the study, adding that remnants of primordial crusts are “not only rare in the meteorite record, but they are also rare today in the asteroid belt.”
“This suggests that the earliest differentiated protoplanets that populated the solar system, as well as most of their debris, were certainly destroyed or subsequently accreted to the growing rocky planets, making the discovery of meteorites originating from primordial crusts an exceptional occurrence,” the researchers noted.
Named after its landing site within Algeria’s Erg Chech dune sea, EC 002 consists of several meteorites that collectively weigh about 70 pounds. After procuring samples of the meteorite, Barrat and his colleagues were able to pin down when this piece of protoplanet crust, which was partially melted as lava, crystallized into a solid form.
Analysis of magnesium and aluminum isotopes in the rock revealed that it dates back about 4.566 billion years ago, making it “the oldest known piece of an igneous crust” ever found, reports the study. For comparison, the next oldest igneous meteorite, called NWA 11119, is about 1.24 million years younger than EC 002, while Earth itself began to emerge several million years after the formation of these rocks.
In addition to its unrivaled age, EC 002 is also notable for its unusual composition. The meteorite is 58 percent silicon dioxide, suggesting that its ancient parent body had a crust made of andesite rock, which is distinct from basalt, a more familiar igneous material that is common in volcanically active regions on Earth.
Barrat and his colleagues note that these andesitic crusts were probably abundant in asteroids and protoplanets during the solar system’s early days, but that they have become extremely scarce in the billions of years since that bygone era. Ancient protoplanets were either incorporated into larger bodies such as Earth or were blasted apart by collisions with other rocks in the tumultuous and crash-prone period of our solar system.
The team estimates that EC 002 was ejected from its parent body by one of these encounters mere decades after the protoplanet’s crust cooled and crystallized, revealing amazing new details about the evolving embryos of planets during a time before Earth existed.
“This meteorite is the oldest magmatic rock analyzed to date and sheds light on the formation of the primordial crusts that covered the oldest protoplanets,” the team concluded.
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