The discovery of a rare meteorite in the Sahara Desert, NWA 12774, has revealed a fascinating chapter in our solar system's history. This angrite meteorite, one of only 68 known angrites, holds the key to a long-lost planet, a protoplanet that may have been as large as Mars. This finding challenges our understanding of planetary formation and evolution, suggesting a unique and distinct pathway for early planets in our solar system.
The meteorite's composition is what initially intrigued scientists. Angrites, with their low silicon dioxide content, were previously thought to originate from asteroids, which are typically small bodies with radii under 200 kilometers. However, the presence of clinopyroxene, a mineral crystal rich in aluminum, indicated that NWA 12774 formed under extreme pressure deep underground, suggesting a much larger parent body.
Further analysis revealed that the pressure conditions required for the formation of this aluminum-rich clinopyroxene were astonishingly high, at least 17.5 kilobars. For comparison, the Mariana Trench, the deepest point on Earth, exerts only around 1 kilobar of pressure. This level of pressure is incompatible with the conditions found in small asteroids, pointing towards a much larger celestial body.
The size of this protoplanet is estimated to be at least 1,000 kilometers in radius, possibly even larger, approaching the size of Mars. The sharp edges and delicate chemical patterns preserved in the crystals within NWA 12774 further support this notion, suggesting that the crystals formed at relatively shallow depths, indicating a larger and more substantial parent body.
This discovery raises intriguing questions about the fate of this protoplanet. One possibility is that it met its end due to a catastrophic event in the early solar system, shattering it into fragments that later became the building blocks of other terrestrial planets, including Earth. The distinct composition of the angrite parent body, with its unique mineralogy, points to a separate evolutionary path in the early history of our solar system.
This finding highlights the importance of continued exploration and study of meteorites. There may be more protoplanets waiting to be discovered, hidden in drawers and awaiting thorough examination. As Aaron Bell, an assistant research professor, suggests, the materials that formed these ancient celestial bodies offer a glimpse into the diverse and fascinating processes that shaped our solar system.
In my opinion, this discovery is a testament to the power of scientific inquiry and the importance of challenging established assumptions. It reminds us that our understanding of the universe is ever-evolving, and there is still much to learn and uncover about the cosmos.
