A meteorite discovered in Africa could be evidence of a lost protoplanet that once orbited our Sun, according to researchers at the University of Colorado at Boulder.
In a recent paper published in Earth and Planetary Science Letters, the team revealed evidence of an ancient protoplanet that may have been as large as Mars based on simulations of how the meteorite sample may have formed.
The four-and-a-half-billion-year-old world carried an unexpected geological makeup, which the researchers say casts doubt on common assumptions regarding planetary evolution.
Protoplanetary Demise
According to the UC Boulder team, the massive protoplanetary body collided with another object four and a half billion years ago, shattering it completely. This is the first definitive evidence of a lost protoplanet in our solar system, based on analysis of the angrite meteorite NWA 12774, a shard of that planetary embryo recovered from the Sahara Desert.
“It’s incredible to think there was once a world this large,” said lead author Aaron Bell, an assistant research professor in the Department of Earth Science at CU Boulder. “We only know it existed because a few fragments of it happened to land on Earth. These meteorites preserved evidence of a completely different pathway through which early planets developed.”
A Rare Meteorite Sample
Angrites, a rare type of volcanic rock, serve as a record of our solar system’s distant past. These rocks began forming only a few million years after the solar system’s birth, making them valuable evidence of this early era. However, they are extremely rare and difficult to find.
NWA 12774 is one of only 68 angrite samples identified among more than 80,000 meteorites cataloged by scientists. Given its rarity, the discovery could potentially reshape how researchers understand these ancient rocks.
Until now, scientists had assumed that angrites originated from relatively small asteroids less than 124 miles (200 kilometers) wide, based largely on their chemical composition. Large rocky planets such as Earth and Mars contain significant amounts of silicon dioxide, while angrites contain very little of the compound.
Unexpected Meteorite Discovery
Researchers began to reconsider those assumptions when they identified clinopyroxene in the meteorite sample. This mineral, commonly found in Earth’s crust and mantle, appeared unusually rich in aluminum, suggesting that it formed under significant pressure deep within a planetary body.
To investigate this unusual characteristic of NWA 12774, the University of Colorado Boulder team recreated the conditions under which the sample could have formed. Their analysis revealed that pressures of at least 17.5 kilobars were required to produce the aluminum-rich clinopyroxene found in the meteorite. For comparison, one kilobar is roughly equivalent to the pressure at the deepest part of Earth’s oceans, near the bottom of the Mariana Trench.
Rethinking Meteorite Origins
The researchers’ discovery proved that at least this particular angrite sample could not have formed inside a small meteorite, as a body with a radius of at least 621 miles would be required to generate the pressure needed to produce the crystals.
Additional evidence suggested the parent body may have been even larger. The crystals’ sharp edges and delicate internal structures indicate they likely formed at relatively shallow depths beneath the surface. Reconciling both the high-pressure conditions and the shallow formation depth suggests that the parent body may have ranged in size from the Moon to Mars.
“There are many meteorites sitting in drawers that haven’t been thoroughly studied, so there were likely more of these protoplanets we don’t know about,” Bell said.
Exactly what happened to this ancient world remains uncertain, but researchers believe it was likely destroyed in a massive collision early in the solar system’s history. Fragments of that lost protoplanet may have later contributed material to other bodies, potentially including Earth itself.
“The materials that formed the angrite parent body are fundamentally different from the ingredients of Earth and Mars,” Bell concluded. “It points to a distinct and separate evolutionary path in planetary formation in the early history of our solar system.”
The paper, “High-Pressure Clinopyroxene in Northwest Africa 12774 and New Geobarometric Evidence for a Planetary Embryo-Sized Angrite Parent Body,” appeared in Earth and Planetary Science Letters on July 1, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.