CAREER: Habitability of the Hadean Earth - A South African perspective

职业：冥古宙地球的宜居性——南非的视角

• 批准号: 2336044
• 负责人: Nadja Drabon
• 金额: $ 88.76万
• 依托单位: Harvard University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-07-01 至 2029-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2336044&HistoricalAwards=false
• 关键词: CAREER; Habitability; Hadean; Earth; South

Earth is the only planet known to harbor life, but when Earth became habitable is still debated. Initially, Earth was uninhabitable because it was covered by a magma ocean and frequently struck by giant impactors. Through time, the first crust crystallized, oceans precipitated, and continents started forming. Yet, we don't know when these processes occurred and when Earth became habitable. This is due to lack of a rock record for Earth’s first ~550 million years of history, the Hadean Eon. The only remaining materials from that time are zircons. Most of our knowledge comes from a single location of Hadean zircons, the Jack Hills in Australia. Recently, the PI’s team discovered Hadean zircon in South Africa. This offers a second lens into the Hadean Eon. Trace elements and isotopes of these zircons will help address processes key to Earth’s habitability. This includes the onset of plate tectonics, outgassing from the mantle, and the emergence of crust above sea level. The proposed research offers symbiotic opportunities to integrate research and educational experiences. The PI will create a museum exhibit to be shown at the Harvard Museum of Natural History and the Ngwenya museum in Eswatini. The research also offers abundant research opportunities for undergraduates from underrepresented minorities. Lastly, improved undergraduate and graduate teaching materials will be disseminated for broader use. The project supports one female early career scientist, one postdoctoral researcher, and 10 undergraduate research assistants.The proposed work will create the first large dataset of Hadean zircon outside the Jack Hills by analyzing a statistically robust number of zircons and by broadening and integrating zircon isotopic (Hf, O, Si) and trace and rare earth element geochemical analyses. The research examines Hadean zircons from the Green Sandstone Bed, South Africa, that were previously collected, extracted, and dated through a separate grant. Firstly, the research will test whether the zircons formed in a stagnant-lid or mobile-lid (i.e., plate tectonics) environment through an integrated study of zircon Hf and O isotopes, trace elements and with modeling. Secondly, it will assess redox-sensitive Ce anomalies in mantle-derived zircons to evaluate the oxidation state of the mantle. A comparison to data from Hadean zircons of the Singhbhum Craton and the Jack Hills will provide constraints on mantle heterogeneity. Thirdly, it will assess isotopic (O, Si) and geochemical proxies (Al, P) to test for the generation of clays and the presence of meteoric waters as proxies for continental emergence through time. The research results will be disseminated through articles in journals, presentations at conferences, and submission to online databases.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

地球是唯一藏有生命的星球，但是当地球变得宜居时，仍在辩论。最初，地球是无法居住的，因为它被岩浆海洋覆盖，经常被巨大的影响器击中。随着时间的流逝，第一个地壳结晶，海洋沉淀并继续形成。但是，我们不知道这些过程何时发生，何时地球变得可居住。这是由于缺乏地球历史上的最初约5.5亿年历史的摇滚记录。从那时起的唯一剩余材料是锆石。我们的大多数知识都来自澳大利亚杰克山的Hadean锆石的一个地点。最近，PI的团队在南非发现了Hadean锆石。这为Hadean Eon提供了第二个镜头。这些锆石的痕量元素和同位素将有助于解决地球可居住性关键的过程。这包括板块构造的发作，从地幔中吹来的，以及海拔以上地壳的出现。拟议的研究为整合研究和教育经验提供了共生的机会。 PI将创建一个博物馆展览，将在哈佛自然历史博物馆和埃斯瓦蒂尼的Ngwenya博物馆展出。这项研究还为来自代表性不足的少数民族的本科生提供了丰富的研究机会。最后，改善的本科和研究生教材将被传播，以供更广泛使用。该项目支持一位女性早期的职业科学家，一名博士后研究员和10位本科研究助理。拟议的工作将通过分析统计上稳定的氧化锆石，扩大和整合氧化锆同位素（HF，o，o，si，si）和稀有的分析，通过分析杰克山外的第一个大型Hadean锆石数据集。从南非的绿色砂岩床上的Hadean锆石先前是通过单独的赠款收集，提取和日期的。首先，该研究将通过对锆石HF和O同位素，痕量元素和建模的综合研究来测试锆石是在停滞范围内或移动范围内形成的锆石。其次，它将评估地幔衍生锆石中对氧化还原敏感的CE异常，以评估地幔的氧化态。与Singhbhum Craton和Jack Hills的Hadean锆石的数据进行了比较，将为地幔异质性提供限制。第三，它将评估同位素（O，Si）和地球化学代理（AL，P），以测试粘土的产生以及流星水的存在，作为随着时间的推移连续出现的代理。该研究结果将通过期刊上的文章，会议上的演讲以及提交在线数据库进行传播。该奖项反映了NSF的法定任务，并通过使用基金会的知识分子和更广泛的影响评估审查标准，通过评估来诚实地支持。