A rare meteorite discovered in the Sahara Desert has provided scientists with the first direct evidence that a massive protoplanet, potentially as large as the Moon or even Mars, once orbited the young Sun before being destroyed in a catastrophic collision more than 4.5 billion years ago. The discovery reshapes our understanding of the solar system's violent early history and suggests that some ancient worlds formed from dramatically different materials than those that built Earth and Mars.
The meteorite, officially designated Northwest Africa (NWA) 12774, belongs to the angrite group, among the oldest volcanic rocks known in the solar system. Angrites formed only a few million years after the solar system emerged approximately 4.56 billion years ago. Of the more than 80,000 meteorites recovered on Earth, only 68 belong to this extraordinarily rare group, making each specimen an invaluable window into the earliest epoch of planetary formation.
Researchers at the University of Colorado Boulder examined tiny crystals inside NWA 12774 and found that they still retained sharp edges and delicate chemical features. These characteristics would normally be destroyed if the crystals had formed deep underground, where intense pressure and heat would have erased such fine details over time. The preservation of these features strongly suggests that the crystals formed relatively close to the surface of their parent body.
This finding carries profound implications for the size of the original world. If volcanic crystals with such pristine features formed near the surface, then the parent body must have possessed a thick mantle and crust above its deeper layers. Scientists estimate that the lost protoplanet had a radius of more than 1,800 kilometers, placing it in the size range between our Moon and Mars. Such a world would have been a significant presence in the early solar system.
The destruction of this ancient body likely occurred during the chaotic period when young planets were still jostling for orbital space, colliding and merging or shattering one another. Fragments from that cataclysmic event scattered throughout the inner solar system, and at least one piece eventually fell to Earth as the meteorite now known as NWA 12774. The journey from protoplanetary debris to Saharan discovery spans billions of years of cosmic history.
Scientists say this discovery also reveals that the early solar system contained worlds built from chemical compositions quite unlike those of the terrestrial planets we know today. The angrite parent body appears to have formed from materials enriched in certain elements while depleted in others, painting a picture of remarkable chemical diversity among the first generation of planets. This challenges simplified models that assumed all rocky worlds in our neighborhood formed from roughly similar building blocks.
The research, published in a leading scientific journal and covered widely by major science outlets, represents a milestone in planetary science. By studying a single rare rock from the Sahara, scientists have effectively reconstructed the existence of an entire lost world, one that played its role in the solar system's dramatic opening chapter before vanishing forever in a violent collision billions of years before humans would ever look up at the stars.
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