科学家发现45亿年前“原始地球”痕迹 为探索太阳系早期演化提供关键线索

Core Insights - A research team led by MIT has made a significant breakthrough by discovering remnants of "primitive Earth" in ancient rock samples dating back approximately 4.5 billion years, published in the journal Nature Geoscience on October 14 [1] - This discovery is expected to fill gaps in human understanding of early Earth and provide important evidence for the origins and evolution of the solar system [1] Group 1 - The early solar system was composed of a rotating disk of gas and dust that gradually coalesced into primitive meteorites, leading to the formation of "primitive Earth" and other planets [1] - A massive impact event, referred to as the "giant impact," occurred less than 100 million years after the formation of "primitive Earth," drastically altering its internal structure and chemical composition [1] Group 2 - The research team analyzed ancient rocks from Greenland and Canada, as well as mantle lava deposits from Hawaii, discovering an unusual chemical marker—anomalous potassium isotope ratios [2] - The potassium isotopes include potassium-39, potassium-40, and potassium-41, with potassium-40 being present in very low amounts in Earth's surface materials [2] - The team observed that the potassium-40 content in the samples was even lower than that found in modern Earth materials, indicating a significant research value [2] Group 3 - To verify the samples as remnants of "primitive Earth," the research team conducted simulations of geological processes affecting potassium isotope ratios [3] - The results showed that the potassium-40 ratio would slightly increase after these processes, aligning closely with the collected rock and lava sample data, supporting the hypothesis that the samples are likely remnants of "primitive Earth" [3] - The potassium isotope characteristics of these samples differ from any meteorites currently known, suggesting that the types of meteorites that contributed to "primitive Earth" have yet to be discovered [3]