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CSEDI Research: Investigations of Volatile Acquisition During Earth's Formation

CSEDI 研究：地球形成过程中挥发性物质获取的研究

基本信息

批准号：
1953992
负责人：
Zachary Sharp
金额：
$ 23.49万
依托单位：
University of New Mexico
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-07-15 至 2024-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1953992&HistoricalAwards=false
关键词：
CSEDI Research Investigations Volatile Acquisition

项目摘要

The singular most important criterion for a habitable Earth-sized planet is the existence of water and other volatiles (e.g., CO2) critical for life. How Earth acquired its water is a hotly-debated field of research, with a number of very different ideas being explored. As the astronomical community continues to find large numbers of Earth-sized exoplanets, the processes by which such bodies acquire volatiles becomes crucial moving forward. It is generally accepted that Earth’s volatiles were sourced by some combination of ingassing from the early solar nebula and delivery from comets and asteroids. The goal of this proposal is to develop a machine learning-based algorithm that uses the abundance and isotopic compositions of multiple volatile elements, including H, He, Ne, N, O, Ar, Kr and Xe to constrain the relative contributions and timing from these potential volatile sources. In doing so, the scientific community will have a better road-map of how volatiles are acquired and how better to search for potential extraterrestrial life.The proposed research plan is to quantify the amounts of volatiles delivered to the Earth early in its history by each of four major sources: chondrites from the asteroid belt, comets from the outer limits of the solar system, direct ingassing from the solar nebula, and radiogenic decay. The research will be performed in three phases. The first phase is development of a comprehensive model of volatile acquisition and loss during Earth’s accretion based on these sources. The model includes a primitive atmosphere derived from the solar nebula, a proto-mantle with magma oceans, and a proto-core. Critical processes include atmosphere gas exchange, water production at the magma surface, core-mantle exchange, late additions from volatile-rich chondrites, comets, radioactive decay, and modifications by the moon-forming event. The second phase places bounds on the contributions of each source, using measurements of present-day volatile abundances and fluxes as constraints in an inversion for source magnitudes. Volatiles to be considered are the isotopes of hydrogen, helium, neon, oxygen, argon, nitrogen, krypton, and xenon. The third phase uses machine learning to train the accretion model to reproduce the observed volatile inventories using the source magnitudes from the second phase. The expected result of this project is a mapping of Earth’s volatiles to their original sources that can serve as a guide for assessing habitability on distant terrestrial exoplanets.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.

对于地球大小的宜居行星来说，最重要的标准是存在对生命至关重要的水和其他挥发物（例如二氧化碳）。地球如何获得水是一个备受争议的研究领域，人们正在探索许多截然不同的想法。随着天文学界不断发现大量地球大小的系外行星，这些天体获取挥发物的过程变得至关重要。人们普遍认为，地球的挥发物是由早期太阳星云的吸入和彗星和小行星的输送的某种组合产生的。该提案的目标是开发一种基于机器学习的算法，使用多种挥发性元素（包括 H、He、Ne、N、O、Ar、Kr 和 Xe）的丰度和同位素组成来限制这些潜在挥发性来源的相对贡献和时间。这样做，科学界将对如何获取挥发物以及如何更好地寻找潜在的外星生命有一个更好的路线图。拟议的研究计划是量化在地球历史早期由四个主要来源中的每一个输送到地球的挥发物的量：来自小行星带的球粒陨石、来自太阳系外围的彗星、来自太阳星云的直接吸收和放射性衰变。该研究将分三个阶段进行。第一阶段是基于这些来源开发地球吸积过程中波动性获取和损失的综合模型。该模型包括源自太阳星云的原始大气、带有岩浆海洋的原始地幔和原始核心。关键过程包括大气气体交换、岩浆表面水的产生、核心-地幔交换、富含挥发物的球粒陨石、彗星的后期添加、放射性衰变以及月球形成事件的改变。第二阶段使用当前挥发性丰度和通量的测量作为源震级反演的约束，对每个源的贡献进行限制。要考虑的挥发物是氢、氦、氖、氧、氩、氮、氪和氙的同位素。第三阶段使用机器学习来训练吸积模型，以使用第二阶段的源震级来重现观察到的挥发性库存。该项目的预期结果是绘制地球挥发物与其原始来源的地图，可以作为评估遥远类地系外行星宜居性的指南。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。