Exploring the Hadean Earth

探索冥古宙地球

• 批准号: 0635969
• 负责人: Timothy Harrison
• 金额: $ 32.03万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-01-01 至 2010-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0635969&HistoricalAwards=false
• 关键词: Exploring; Hadean; Earth

The first 500 million years of Earth history (4.5 to 4.0 billion years), known as the Hadean Eon, is the planet's 'dark age' as no rock older than 4 billion years are known in the geologic record. However, sand-grain sized crystals of the mineral zircon are found in younger quartzite rocks that are dated to almost as old as the Earth itself. Preliminary analyses suggest the possibility that the very early Earth shared more in common with present day than previously thought. This surprising result requires detailed examination, but Hadean grains are very rare, making up only about one part in a million of the sedimentary rock. Following an intensive analysis program, the lead scientist and his team have archived several hundred Hadean zircons and in this project, they plan to undertake experiments that may give us unprecedented insights into Earth's earliest evolution. The questions to address are the following: 1) Did early Earth differentiation include massive production of continental crust? 2) Did a mechanism akin to plate tectonics operate during the Hadean? 3) Why are rocks older than 4 billion years non-existent? 4) When did the atmosphere form? 5) Were there oceans during the Hadean Eon? 6) Are any of these ancient zircons of extra-terrestrial origin? To address these questions, the investigator will undertake nanoscale imaging of trace elements distributions in these zircons together with refined isotopic measurements.This project showcases scientific and technical leadership in a field of global interest and aids in capturing the imagination of young people considering a career in science. Research outcomes are potentially of great public interest and could be akin to the results of a planetary exploration mission if the existing paradigm of Hadean Earth is overturned. Within the scientific community, evidence that the Earth was potentially habitable during the Hadean Eon would radically alter our views of the constraints on the emergence of life on this and other planets and lead genomic researchers to consider planting the roots of phylogenic trees a good deal deeper.

地球历史的最初5亿年(45亿到40亿年)，被称为Hadean Eon，是地球的“黑暗时代”，因为在地质记录中没有超过40亿年的岩石。然而，砂粒大小的矿物锆石晶体是在较年轻的石英岩中发现的，这些岩石的年代几乎与地球本身一样古老。初步分析表明，非常早期的地球与今天有更多相似之处的可能性比之前认为的要多。这一令人惊讶的结果需要详细的检查，但哈迪亚颗粒非常罕见，仅占沉积岩的百万分之一。经过密集的分析程序，首席科学家和他的团队已经归档了数百个哈迪亚锆石，在这个项目中，他们计划进行实验，可能会让我们对地球最早的演化有前所未有的了解。要解决的问题如下：1)早期的地球分异是否包括大陆地壳的大量产生？2)类似于板块构造的机制是否在Hadean期间运行？3)为什么40亿年以上的岩石不存在？4)大气是什么时候形成的？5)Hadean Eon期间有海洋吗？6)这些古老的锆石中有来自地外的吗？为了解决这些问题，研究人员将对这些锆石中的微量元素分布进行纳米级成像，并进行精细的同位素测量。这个项目展示了一个全球感兴趣的领域的科学和技术领先地位，并有助于激发年轻人考虑从事科学事业的想象力。研究成果可能会引起公众的极大兴趣，如果现有的海德地球范式被推翻，研究结果可能类似于行星探索任务的结果。在科学界，有证据表明，在Hadean Eon时期，地球可能是宜居的，这将从根本上改变我们对这颗行星和其他行星上生命出现的限制的看法，并促使基因组研究人员考虑将系统发育树的根植得更深。