The discovery of a rare meteorite, NWA 12774, has revealed a fascinating insight into the early solar system. This angrite meteorite, found in the Sahara Desert, holds the key to understanding a lost planetary embryo, or protoplanet, that once orbited our sun. What makes this finding truly remarkable is the geological makeup of the meteorite, which challenges long-held assumptions about planetary evolution.
Aaron Bell, an assistant research professor at the University of Colorado Boulder, highlights the significance of this discovery. "It’s incredible to think there was once a world this large," he says. "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."
The NWA 12774 meteorite is an angrite, a rare type of volcanic rock that formed within the first few million years of the solar system's existence. Angrites are intriguing because they contain very little silicon dioxide, or silica, which is a major component of terrestrial planets like Earth and Mars. This unique chemistry led scientists to believe that angrites always originated from asteroids, which are much smaller than the protoplanet in question.
However, Bell and his team made a groundbreaking discovery while studying NWA 12774. They found that the meteorite contained clinopyroxene, a mineral crystal rich in aluminum, indicating that it formed under immense pressure deep underground. The pressure conditions required for this formation were astonishingly high, at least 17.5 kilobars, which is far beyond what can be achieved within a small asteroid.
This finding led the researchers to conclude that the parent body of the angrites must have been a massive celestial body, at least 1,000 kilometers in radius. Some calculations even suggested a radius of 1,800 kilometers or more, making it comparable in size to Earth's moon or even Mars. This implies that the protoplanet was significantly larger than previously thought, challenging our understanding of planetary formation.
The sharp edges and delicate chemical patterns preserved in the crystals of NWA 12774 further support the idea of a larger, more substantial parent body. These features suggest that the crystals formed at relatively shallow depths, indicating a larger world with a more complex geological history.
The implications of this discovery are profound. It suggests that there may be other protoplanets waiting to be discovered, as Bell notes, "There are many meteorites sitting in drawers that haven’t been thoroughly studied, so there were likely more of these protoplanets we don’t know about."
The end of this protoplanet remains a mystery. One theory is that a catastrophic event in the early solar system shattered it, and its fragments became the building blocks of other terrestrial planets, including Earth. This idea highlights the dynamic and violent nature of the early solar system, where planets were constantly evolving and interacting.
In conclusion, the NWA 12774 meteorite has provided invaluable evidence of a lost protoplanet, challenging our understanding of planetary formation and evolution. It raises intriguing questions about the early solar system and the diverse pathways through which planets can develop. As Bell suggests, further study of meteorites and their geological characteristics may reveal more about the fascinating history of our solar system.
