A meteorite found in the Sahara Desert has provided the first direct evidence of a massive protoplanet that orbited the young Sun more than 4.5 billion years ago. The object, comparable in size to the Moon, was destroyed in a collision, leaving fragments that reached Earth. Researchers say the discovery reveals a previously unknown path in early planet formation.
Scientists analyzed the angrite meteorite Northwest Africa 12774 and identified high-pressure minerals that could only form deep inside a large body. Calculations showed the parent world had a radius of at least 1,000 kilometers and likely exceeded 1,800 kilometers.
Aaron Bell of the University of Colorado Boulder said the preserved crystals indicate the material formed relatively close to the surface of this ancient world. The findings were published in the journal Earth and Planetary Science Letters.
Angrites are rare volcanic rocks that formed within a few million years of the Solar System’s birth. Their unusual low-silica composition had previously suggested origins in small asteroids, but the new pressure data overturned that view.
Bell noted that many other meteorites remain unstudied and could reveal additional lost protoplanets. The materials from this body differ fundamentally from those that built Earth and Mars.