Angrite Meteorite NWA 12774 Tied to Lost World

Angrite meteorite NWA 12774 shimmers. This 16-ounce (454-gram) space rock shimmers like a rainbow kaleidoscope under cross-polarized light, but it's hiding a far more extraordinary story, and researchers at the University of Colorado Boulder captured that display. Plucked from the Sahara Desert in 2019, this angrite meteorite NWA 12774 might be the first solid fragment of a long-dead protoplanet that once circled the young sun.

A Shard from a Dead Planet

NWA 12774 belongs to an almost vanishingly rare class. The angrites account for just 0.09% of all meteorites ever recovered on Earth. They are also among the oldest rocks in the solar system, forged within the first few million years after the system’s birth 4.56 billion years ago. Unlike most asteroids and rocky planets, they carry exceptionally low levels of silica, the silicon dioxide that is a fundamental building block of terrestrial worlds.

It's from Northwest Africa. But the NWA designation, standard for any meteorite found in that vast region, doesn't reveal what lay inside, and that immediately set scientists on a new trail.

The Rarest Meteorites

Angrites have long puzzled researchers. But their composition doesn't match anything we see in the main asteroid belt today, and previously the leading idea was that these rocks broke off from small asteroids, bodies that simply cooked up a different mineral recipe.

• Formed within just a few million years of the solar system’s ignition
• Exceptionally low silica content, unlike typical asteroids or planets
• Represent a mere 0.09% of the roughly 80,000 cataloged meteorite falls

Aaron Bell, a petrologist at the University of Colorado Boulder, and his team decided to conduct a deeper investigation of the meteorite sample NWA 12774. They've rewritten angrites' origin story.

A Collision High-Pressure Clue

Researchers found clinopyroxene. This mineral, common in Earth's crust and mantle, was unusually rich in aluminum, and it's an enrichment that only happens under pressures far beyond what a small asteroid could ever generate. So the parent body possibly absorbed a massive, high-energy collision to produce that signature.

Stone's edges are sharp, unweathered. Bell's group calculated pressures locked inside clinopyroxene require radius at least 621 miles (1,000 km), and since sample's torn from a surface layer, the original object's radius likely reached up to 1,118 miles (1,800 km). But those sharp edges push the estimate even higher.

• Minimum parent body radius: 621 miles (1,000 km)
• Likely true radius based on surface origin: up to 1,118 miles (1,800 km)
• Earth’s Moon radius: 1,080 miles (1,737 km)
• Mars radius: 2,106 miles (3,390 km)

The numbers place the angrite meteorite NWA 12774’s birthplace firmly in the category of a planetary embryo;a body as large as the Moon, maybe even approaching the size of Mars.

Rethinking Planetary Origins

The old hypothesis is wrong. But the angrites, including NWA 12774, didn't form on a modest chunk of rock; they crystallized on a world that was busy becoming a planet, a protoplanet that followed a completely different evolutionary track.

“It’s incredible to think there was once another world this large,” Bell said. “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 Separate Evolutionary Path

The minerals in NWA 12774 tell a starkly unfamiliar tale. Silica was minor. But the raw materials that built the angrite parent body weren't like those that formed Earth or Mars, and aluminum-rich clinopyroxene became the defining fingerprint of a violent genesis.

“The materials that formed the angrite parent body are fundamentally different from the ingredients of Earth and Mars,” Bell said. “It points to a distinct and separate evolutionary path in planetary formation in the early history of our solar system.”

But it wasn't just smaller. The protoplanet that birthed the angrite meteorite NWA 12774 was a fully independent experiment in planet building, and its catastrophic end scattered its remains across the inner solar system.

What Happened to the Lost World?

So the precise fate of that vanished protoplanet remains murky, but the thinking goes that it once orbited the sun before smashing into another large body billions of years ago and that the collision shattered it into countless fragments, some of which eventually rained down on Earth.

They're everywhere. But researchers suspect some debris may have been swept up as raw material for other growing planets, including our own, and crumbs of a dead world might be baked into very crust beneath our feet.

So NWA 12774's tiny. This technicolor messenger's rainbow hues, visible only under polarized light, beam across 4.5 billion years to remind us that the early solar system was filled with strange, ambitious worlds that never made it. A few grams of rock, a kaleidoscope of pressure and light, and suddenly a lost planetary embryo feels just a little less like science fiction.