A Lost World: Evidence of a Mars-Sized Protoplanet Found in Ancient Meteorite
Analysis of a rare meteorite suggests a protoplanet as large as the Moon or Mars existed 4.5 billion years ago, before being destroyed.
Scientists have uncovered compelling evidence of a long-lost protoplanet, a "world this large" that formed in the earliest days of our solar system. The discovery, detailed in a study published in Earth and Planetary Science Letters, comes from an unlikely source: a meteorite found in the Sahara Desert.
The Evidence in the Rock
The key to the discovery is the NWA 12774 angrite meteorite. Angrites are among the oldest known volcanic rocks in the solar system. They are exceptionally rare, and this specific sample held a crucial secret.
Analysis revealed it contains aluminum-rich clinopyroxene, a mineral that only forms under immense pressure—at least 17.5 kilobars. Such pressure could not have occurred within a small asteroid. The parent body of this meteorite must have been a planetary-scale object with a radius of at least 1,000 kilometers (620 miles). Given the preserved sharp crystal edges in the sample, scientists believe the radius may have exceeded 1,800 kilometers (1,118 miles), making it comparable in size to Mars.
"It's incredible to think there was once a world this large." - Aaron Bell, Assistant Research Professor, University of Colorado Boulder
A Missing Piece of Planetary Evolution
This protoplanet wasn't just big; it was chemically unique. The angrite meteorite is composed of material fundamentally different from that of Earth or Mars.
"These meteorites preserved evidence of a completely different pathway through which early planets developed."
This distinct chemistry, including a low silicon dioxide content, points to a separate and unique evolutionary path for this celestial body. "The materials that formed the angrite parent body are fundamentally different from the ingredients of Earth and Mars," said Bell. "It points to a distinct and separate evolutionary path in planetary formation."
A Violent End
This "lost world" did not survive the chaotic early days of the solar system. The evidence suggests the protoplanet was shattered by a catastrophic collision event. Its fragments, now scattered, likely became building blocks for other planets—or, in the case of this rare angrite, fell to Earth as a messenger from a forgotten era.