Meteorite fragments fall all over the Earth. But among the nearly 80,000 meteorites discovered so far, only a handful are known as angrites, and at least one of them may be the remnant of a long-lost protoplanet in our solar system, a new study suggests.
Researchers read NWA 12774An angrit obtained in the Sahara desert noticed that the pressures required to create the chemical structure of the fragment could not exist inside the smaller asteroids. Moreover, the sharp, delicate crystals in the angriite indicate that it was born at relatively shallow depths. a final paper Published in the journal Earth and Planetary Science Letters, the team presented an unexpected possibility – could angrit once belong to a long-lost planetary embryo in our solar system?
“Meteorites are actually a library of information about the formation and evolution of the early solar system” Aaron S. Bellfirst author of the study and a geoscientist at the University of Colorado Boulder, told Gizmodo. “In particular, angrites preserve a record of the processes that took place at the very beginning of planetary formation.”
Ancient oddities
Angrites are among the oldest basaltic meteorites, Bell explained, and isotopic studies indicate they are about 4.56 billion years old. However, their chemical composition sets them apart from other basalts found on Earth, the Moon, and even Mars. For example, lignites have lower levels of silica and different mineral chemistry, he added.
But NWA 12774 was even stranger. Bell noted that this particular angrite contained remarkably high levels of aluminum in clinopyroxene, a mineral found beneath the Earth’s surface — “a chemical signature typically associated with high-pressure crystallization.” “This observation suggested that a small asteroid formed under unexpected conditions and instead pointed to a larger parent body.”
When the stone cracks
To really drive this point home, Bell and colleagues set up an experiment to confirm how much pressure would be required to crystallize aluminum-rich clinopyroxene. Specifically, the team developed and tested a computational thermodynamic tool and integrated the measured compositions of NWA 12774. Doing so allowed the researchers to “take the composition of individual mineral grains and use thermodynamics to constrain the conditions under which they formed, and thus the size of the body in which they formed,” he said.
Tests revealed that the crystals needed a pressure of at least 17.5 kilobars. To put this into perspective, the pressure at the bottom of the Mariana Trench is about one kilobar. university statement on the findings. Further calculations indicated that the angrite must have come from a parent body with a radius of at least 621 miles (1,000 kilometers). of the Moon for comparison medium radius is approximately 1,080 miles (1,738 km).
A lost planet?
This may actually be a conservative estimate. X-ray images of the fragment showed well-preserved, sharp crystal edges that did not survive deep in the earth, the statement explained. In this case, the parent body could be as large as Mars, with a radius of 2,050 miles (3,300 km).
“These meteorites preserved evidence of a completely different way that the early planets evolved,” Bell said. “There’s a lot of meteorites sitting around in orbit that haven’t been thoroughly studied, so there’s likely to be more of these protoplanets that we don’t know about.”
Of course, we won’t be able to turn back time to see NWA 12774 actually fall from a long-lost part of the solar system. Still, angrites—and for that matter, any ancient meteorite—are unique artifacts that provide valuable insight into the geochemistry of the early solar system. Bell told Gizmodo that it’s a “remarkable opportunity.”
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