GLOW: Loss of volatiles from the Hadean Earth and the redox evolution of the early atmosphere

辉光：冥古宙地球挥发物的损失和早期大气的氧化还原演化

• 批准号: 2224727
• 负责人: Jun Korenaga
• 金额: $ 29.87万
• 依托单位: Yale University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-06-01 至 2025-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2224727&HistoricalAwards=false
• 关键词: GLOW; Loss; volatiles; Hadean; Earth; GLOW; Loss; volatiles; Hadean; Earth

Some researchers think rocky planets like Earth must have formed by giant impacts, and that the last of such impacts to Earth resulted in the formation of the Moon. After this impact, the early Earth likely experienced continued bombardment of leftover planetesimals. These bombardments are called late accretion impacts, some of which could be as large as the Moon. Both giant impacts and late accretion impacts are very energetic. Each of them can melt a large fraction of Earth’s mantle, and the surface can be as hot as 5,000-15,000 K. Such a hot surface would help the atmosphere escape to space, which is important for the surface environments of the early Earth. The lightest element - hydrogen - is most easily removed by this process, so in the presence of surface water the impact-driven atmospheric loss could result in the oxidation of Earth. The notion of such catastrophic evaporation is generally accepted in the exoplanet field, but it has not gained traction in the Earth sciences. This research will incorporate novel ideas developed in the exoplanet atmospheric literature to the study of the Hadean Earth (the first 500 million years of Earth history). The redox state of the atmosphere is also important for the emergence of life on Earth. Thus, our modeling of Earth evolution in the aftermath of high-energy impacts could provide a timely reference frame for those currently exploring exoplanets for signs of life. This project will support a postdoctoral researcher and contribute more broadly through mentoring New Haven Science Fair high school students.Most research on the removal of volatiles from Earth’s early atmosphere focuses on a narrow temperature range of 1500–2500 K when mass loss is inefficient and limited by diffusion above the turbopause. The extreme thermal conditions right after high-energy impacts would quickly dissipate in a few hundred years, but even in this short period, the atmospheric loss can be on the order of several Earth oceans. The proposed research aims to quantify this extreme period of the early Earth, by conducting a fluid dynamical simulation of Earth’s post-impact atmosphere that incorporates the interior heat and the incoming X-ray and ultraviolet irradiation from our Sun. Because Earth’s early atmosphere would chemically interact with the magma ocean below, the evolution of the atmosphere will influence the redox evolution of the mantle. The relevant parameter space will be explored to assess how the different evolutionary pathways of the Hadean Earth comply with available geological data, and with other theoretical possibilities suggested in the literature. This will provide an unprecedented insight into the properties of the Hadean Earth and, in doing so, reveal how the loss of volatiles may be the missing nexus that explains why Earth is unique among the planets in our solar system. This proposal was submitted to CH in response to DCL 22-032: Dear Colleague Letter: Geoscience Lessons for and from Other Worlds (GLOW).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.

一些研究人员认为，像地球这样的岩石行星一定是由巨大的影响形成的，而对地球的最后影响导致了月球的形成。在这种影响之后，早期地球可能会继续轰炸剩下的行星。这些轰炸称为后期积聚影响，其中一些可能与月球一样大。巨大的影响和后期的积聚影响都非常有活力。他们每个人都可以融化地球地幔的大部分，并且表面可以高至5,000-15,000 k。这样的热表面将有助于大气逃到太空，这对于早期地球的表面环境很重要。最轻的元素 - 氢 - 最容易通过此过程去除，因此在存在地表水的情况下，冲击驱动的大气损失可能导致地球的氧化。这种灾难性经济的概念通常在外部领域被接受，但在地球科学中尚未获得关注。这项研究将融合外部大气文献中发展的新思想与哈迪斯地球的研究（地球历史的前5亿年）。大气的氧化还原状态对于地球上生命的出现也很重要。这，我们对高能量影响后的地球演变建模可能会为当前探索外部行星的人及时参考框架。该项目将支持一名博士后研究人员，并通过对纽黑文科学博览会高中生进行心理贡献。关于从地球早期气氛中挥发物的大多数研究集中在狭窄的温度范围为1500-2500 K时，当质量损失无效且受涡轮上的扩散限制的限制。高能撞击后的极端热条件将在几百年内迅速消失，但是即使在短时间内，大气损失也可以依靠几个地球海洋。拟议的研究旨在通过对地球后影响大气层进行流体动态模拟来量化地球早期的极端时期，该模拟结合了内部热量以及来自太阳的X射线和紫外线的X射线和紫外线照射。由于地球的早期大气将与下面的岩浆海洋化学相互作用，因此大气的演变将影响地幔的氧化还原演化。将探索相关的参数空间，以评估Hadean Earth的不同进化途径如何符合可用的地质数据，并与文献中建议的其他理论可能性相符。这将为Hadean地球的性质提供前所未有的见解，并在此揭示挥发物的损失可能是缺失的Nexus，这解释了为什么地球在太阳系中的行星中是独一无二的。该提案是针对DCL 22-032提交的：亲爱的同事信：其他世界和来自其他世界的地球科学课程（Glow）。该奖项反映了NSF的法定任务，并被认为是通过基金会的知识分子优点和更广泛的影响审查标准通过评估来评估的。