The Northwest Africa (NWA) 12774 meteorite, a 454-gram rock discovered in the Sahara Desert in 2019, provides the first definitive evidence of a lost protoplanet that existed shortly after the solar system formed 4.5 billion years ago. According to research published by the University of Colorado Boulder, this rare angrite meteorite reveals that early planetary bodies developed under conditions vastly different from those of Earth or Mars.
How did scientists identify this lost world?
Researchers identified the meteorite as an angrite, a rare class of volcanic rock. Out of more than 80,000 meteorites found on Earth, only 68 are classified as angrites, according to data from the University of Colorado Boulder. By measuring radioactive elements within NWA 12774, scientists determined the rock formed within a few million years of the solar system’s birth.
The key to the discovery was the presence of clinopyroxene crystals. Aaron Bell, an assistant research professor in the Department of Earth Science at CU Boulder, notes that these crystals indicate the rock formed under extreme pressure—at least 17.5 kilobars. This is more than 17 times the pressure found at the bottom of the Mariana Trench, a condition impossible to achieve on a small asteroid.
Angrites are among the oldest volcanic rocks in the solar system, yet they contain very little silica, the primary ingredient in the crusts of Earth and Mars. This chemical anomaly led scientists to initially assume they originated from small asteroids with radii under 200 kilometers.
What does this reveal about planetary evolution?
The internal structure of the crystals suggests they formed at relatively shallow depths, yet required massive pressure to crystallize. This contradiction implies the “lost world” was significantly larger than previously thought. Scientists estimate the protoplanet may have had a radius of approximately 1,800 kilometers, making it comparable to the size of the Moon and potentially approaching the scale of Mars.
This finding challenges traditional models of early solar system development. While rocky planets like Earth and Mars are well-studied, NWA 12774 suggests that other, now-shattered worlds followed entirely different geological pathways. According to Aaron Bell, these fragments likely integrated into other rocky planets, including Earth, following violent collisions in the early solar system.
Why are there so many undiscovered protoplanets?
The discovery of NWA 12774 suggests that the building blocks of our solar system are still waiting to be found in laboratory collections. Many meteorites currently sitting in drawers have yet to be studied with modern, high-precision techniques.
As researchers apply new analytical methods to these existing samples, the inventory of known “lost worlds” is expected to grow. This shift in focus from broad planetary surveys to the microscopic analysis of rare meteorites represents a change in how geoscientists reconstruct the volatile history of our cosmic neighborhood.
Frequently Asked Questions
What is an angrite?
An angrite is a rare type of volcanic meteorite that formed in the very early stages of the solar system. Only 68 have been identified out of over 80,000 discovered meteorites.
How big was the protoplanet that created NWA 12774?
Based on the high-pressure mineral signatures, scientists estimate the parent body had a radius of about 1,800 kilometers, similar to the Moon.
Where was the meteorite found?
NWA 12774 was discovered in the Sahara Desert in 2019.
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