A 4.56 billion year old angrite from the Sahara carries mineral chemistry consistent with deep interior formation on a large parent body, sharpening the timeline of how the inner Solar System built and lost its earliest worlds.
Four and a half billion years ago, something the size of the Moon formed fast in the infant Solar System, and then shattered. There is no image of it, no orbit, no surviving name. The only material witness is a fist-sized stone pulled from the Saharan sand in 2019, cataloged as NWA 12774, and now the subject of a study in Earth and Planetary Science Letters that Scientific American reported on this week.
The rock is old, about 4.56 billion years, which puts its crystallization within the first few million years after the Sun ignited. It is also rare. NWA 12774 belongs to a class of meteorites called angrites, and angrites are scarce: fewer than 70 of the roughly 80,000 meteorites cataloged worldwide fall into the class. Most meteorites are pieces of ordinary asteroids. Angrites are achondrites, igneous rocks that already melted and re-solidified, which means they had to form on a parent body large and hot enough to differentiate. That is the first clue. The second is in the mineralogy.
A research group analyzed NWA 12774's chemical composition and read it as a high-pressure signature, the kind of mineral chemistry that forms deep inside a sizable body rather than near the surface of a small one. In Scientific American's reporting by Jenna Ahart, independent researchers describe the result as consistent with origin on a parent body possibly the size of the Moon, a protoplanet that, the authors argue, accreted within roughly four million years of the Solar System's formation and was later destroyed. The fragments that survived, including NWA 12774, eventually fell to Earth, with this particular stone landing in the Sahara in 2019.
If the reading holds, the early inner Solar System built large bodies faster than the surviving geological record usually shows, and broke them apart before they could be preserved. The Moon-sized estimate, paired with a four-million-year accretion window, is what makes the claim matter for early-Solar-System timelines: it puts a tight ceiling on how quickly large protoplanets could accrete and then be lost.
It is also a testable claim, not a confirmed one. Angrites are inferred to come from a single parent body, but no such body has been identified in the asteroid belt or in any surviving impact record. The high-pressure reading is an inference from mineral chemistry in one rock. A second angrite with the same fingerprint would strengthen the case; a divergent chemistry in another angrite would weaken it. The honest framing is that the parent body is plausible, well-motivated, and still missing.
What the study does establish is a way to look. If high-pressure mineral assemblages can identify angrites as deep-interior samples rather than shallow crustal ones, the class becomes a probe for the interior conditions of a vanished protoplanet, not just a curiosity in the meteorite cabinet. The early Solar System was not a quiet place, and angrites may carry the surviving chemistry of a world that grew up fast and broke apart before it finished.
The thin-slice image of NWA 12774, photographed under cross-polarized light by John Kashuba and published with the Scientific American story, shows a bright mineral mosaic, the kind of texture that records a slow cool deep inside a parent body. Reading that texture as evidence of a Moon-sized protoplanet is the new claim. Confirming it will take more rocks, more chemistry, and probably more Saharan sand.