The discovery of a rare meteorite, NWA 12774, has revealed a lost world from our solar system's early days. This angrite meteorite, found in the Sahara Desert, holds the key to understanding a protoplanet that once orbited the sun, possibly as large as Mars. The unique geological makeup of NWA 12774 challenges long-held assumptions about planetary evolution, suggesting a distinct and separate evolutionary path in the early history of our solar system.
What makes this finding remarkable is the meteorite's composition. Angrites, the type of NWA 12774, are among the oldest volcanic rocks in the solar system, forming just a few million years after the solar system's inception. They are incredibly rare, making up only 0.084% of all meteorites discovered on Earth. The low silicon dioxide (silica) content in angrites, unlike other rocky planets, initially led scientists to believe they originated from asteroids with radii less than 200 kilometers.
However, a closer examination of NWA 12774 revealed clinopyroxene, a mineral crystal rich in aluminum, indicating formation under extreme pressure deep underground. The pressure conditions required for this aluminum-rich clinopyroxene to form were astonishingly high, at least 17.5 kilobars, far exceeding the crushing pressure at the bottom of the Mariana Trench. This high pressure could not have existed within a small asteroid, suggesting the angrite parent body was significantly larger, possibly stretching beyond 1,800 kilometers in radius, comparable to the size of Mars.
The sharp edges and delicate chemical patterns of the crystals inside NWA 12774 further support this conclusion. These features suggest that the crystals formed at relatively shallow depths, indicating the protoplanet's size was even more substantial. The materials that formed the angrite parent body are fundamentally different from those of Earth and Mars, pointing to a distinct and separate evolutionary path in planetary formation.
This discovery raises intriguing questions about the protoplanet's fate. One possibility is that a catastrophic event in the early solar system shattered it, with its fragments becoming the building blocks of other terrestrial planets, including Earth. The existence of this protoplanet challenges our understanding of planetary formation and highlights the diversity of early solar system bodies.
In conclusion, the NWA 12774 meteorite provides invaluable insights into the early solar system and the formation of planets. It suggests that our understanding of planetary evolution may need revision, and there are likely more protoplanets waiting to be discovered. This finding underscores the importance of continued exploration and research in astrobiology and planetary science.
