A rare meteorite recovered from the Sahara Desert has revealed compelling evidence for a long-lost world that existed during the solar system’s earliest days.
About 4.5 billion years ago, a large planetary body, potentially as large as the Moon or even Mars, orbited the Sun before colliding with another object and breaking apart.
Now, researchers reporting in Earth and Planetary Science Letters say they have found the first direct evidence that this lost protoplanet once existed. The discovery suggests that some early worlds formed and evolved in ways very different from Earth and other rocky planets.
“It’s incredible to think there was once a world this large,” said Aaron Bell, an assistant research professor in the Department of Earth Science at the University of Colorado 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 Meteorite From a Lost World
The evidence comes from a meteorite found in the Sahara Desert called Northwest Africa (NWA) 12774, an extremely rare type of meteorite known as an angrite.
Angrites are among the oldest volcanic rocks in the solar system. They formed just a few million years after the solar system emerged about 4.56 billion years ago. They are also remarkably uncommon. Of the more than 80,000 meteorites discovered on Earth, only 68 have been identified as angrites.
Scientists have long been puzzled by their chemistry. Unlike Earth, Mars, and other rocky planets, angrites contain very little silicon dioxide, or silica, a major component of nearly all known terrestrial planets.
Because of that unusual composition, researchers previously believed angrites originated from relatively small asteroids with radii of less than 200 kilometers (124 miles).
Unexpected Evidence Deep Within the Rock
While analyzing NWA 12774, Bell and his team found clinopyroxene, a mineral commonly present in Earth’s crust and mantle. What stood out was its unusually high aluminum content, which indicates the mineral formed under intense pressure deep inside a planetary body.
The researchers modeled the conditions required to produce the meteorite’s mineral composition.
Their results showed that the aluminum rich clinopyroxene could only have formed at pressures of at least 17.5 kilobars. By comparison, pressure at the bottom of the Mariana Trench, Earth’s deepest ocean location, is about 1 kilobar.
Such pressures would be impossible inside a small asteroid. Instead, the calculations indicate that the angrite parent body had a radius of at least 1,000 kilometers (621 miles).
A Planetary Body Larger Than Expected
Additional evidence suggested the source body may have been even larger. Crystals within NWA 12774 retained sharp edges and subtle chemical patterns that likely would not have survived if they had formed deep below the surface.
That finding suggests the crystals developed at relatively shallow depths, meaning the parent body would have needed to be significantly larger to generate the required pressures.
Under this interpretation, the angrite parent body may have exceeded 1,800 kilometers (1,118 miles) in radius. That would make it comparable in size to the Moon and possibly approaching Mars, which has a radius of 3,300 kilometers (2,050 miles).
“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.
Researchers still do not know what ultimately happened to the ancient world. One possibility is that it was destroyed in a major collision early in solar system history, with its fragments later becoming part of other rocky planets, including Earth.
“The materials that formed the angrite parent body are fundamentally different from the ingredients of Earth and Mars. It points to a distinct and separate evolutionary path in planetary formation in the early history of our solar system,” Bell said.
Reference: “High-pressure clinopyroxene in Northwest Africa 12774 and new geobarometric evidence for a planetary embryo-sized angrite parent body” by Aaron S. Bell, Laura Waters and Mark Ghiorso, 10 April 2026, Earth and Planetary Science Letters.
DOI: 10.1016/j.epsl.2026.120029
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