CSEDI Collaborative Research: Understanding of the effects of large planetesimal collisions on Hadean Earth mantle dynamics

CSEDI合作研究：了解大型星子碰撞对冥古宙地幔动力学的影响

• 批准号: 2102777
• 负责人: Jun Korenaga
• 金额: $ 33.91万
• 依托单位: Yale University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-07-01 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2102777&HistoricalAwards=false
• 关键词: CSEDI; Collaborative; Research; Understanding; effects

The evolution of the Hadean Earth (4-4.5 billion years ago) was shaped by large-scale interplanetary collisions, characterized by impactors with diameters ranging from 1,000 to 4,000 km. The defining characteristics of the Earth, such as oceans, continents, life, and plate tectonics are likely to have appeared for the first time on the Hadean eon. It thus seems inevitable that their emergence would have been affected by these early collisions, though to what extent they were affected remains an open question. In particular, little understood are the effects of these collisions on the internal evolution of the Earth. Collisions are thought to have contributed significantly to the abundance of highly iron-loving elements (e.g., Au, Ir, Ru) in the Earth’s mantle, but the details of their delivery through impacts are not fully understood due to complex mixing processes that arise when a projectile collides with the early Earth. In addition, it is not well-understood how the long-term evolution of the Earth’s mantle could have responded to the injection of materials derived from the impactors. This project introduces an innovative computational approach that combines impact simulations with models that explore the long-term evolution of the Earth’s interior to quantify the delivery of highly iron-loving elements, their distribution in the mantle, and the total mass of late accreted materials. These results allow for an increased understanding of the Hadean Earth surface environment. Moreover, the connections between short-term impact dynamics and long-term mantle dynamics may shed light on the origin of anomalies in the mantle (such as the large low-shear-velocity provinces, which are the most significant anomalies on the deep mantle), the dynamics of mantle plumes, and the history of the geomagnetic field. This project also provides support for interdisciplinary training of a graduate student, an undergraduate internship where the Southwest Research Institute will host 1-2 geophysics major from Yale University, and a series of movies that visualize planetesimal impacts and mantle dynamics for education outreach.The geophysical evolution of Hadean Earth was controlled by large-scale collisions and mantle dynamics, but the interplay of these processes remains largely unexplored. The Earth’s protracted bombardment of leftover planetesimals after the Moon-forming giant impact, called “late accretion”, is supported by the lunar cratering record and is required to explain the abundance of as well as the chondritic proportions of highly siderophile elements (HSEs) in the present-day mantle. Recently, based on impact simulations with smooth-particle hydrodynamics (SPH), the late accreted mass has been suggested to be two to five times higher than previously thought, because the metallic cores of large differentiated planetesimals, where the bulk of HSEs reside, are not efficiently mixed into the mantle. Such an upward revision of late accreted mass could dramatically modify our understanding of the Hadean Earth. This suggestion based on SPH simulations is, however, still provisional because important complications arising from long-term mantle dynamics are not incorporated. Thus, the delivery of HSEs, their distribution in the mantle, and the total mass of the late accretion are still wide-open questions, with important consequences on the Hadean Earth surface environment. This project aims to achieve the following two major objectives: (1) to quantify the fate of differentiated planetesimal cores during impacts, by re-evaluating SPH simulations including the physics of fragmentation, and (2) to understand the long-term fate of fragmented metallic blobs by conducting systematic mantle mixing simulations. The primary goal of this project is to determine the absolute scale of planetesimal impact history, but achieving this goal will also help to address a wide range of important questions, from the habitability of the early Earth to the origin of deep geochemical reservoirs.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.

大型地球（4-45亿年前）的演变是由大规模行星际碰撞塑造的，其特征是直径为1,000至4,000公里的撞击器。大地的定义特征，例如海洋，持续，生命和板块构造，可能是第一次出现在Hadean Eon上。因此，似乎不可避免地会受到这些早期碰撞的影响，尽管他们在多大程度上影响了一个公开的问题。特别是，这些碰撞对地球内部进化的影响很少。人们认为，碰撞对地球地幔中的丰富丰度（例如Au，ir，ru）产生了重大贡献，但是由于弹丸与早期地球碰撞时出现的复杂混合过程，因此无法完全理解其通过撞击传递的细节。此外，这并不理解地球地幔的长期演变如何应对从撞击器中衍生的材料的注入。该项目引入了一种创新的计算方法，该方法将影响模拟与探索地球内部长期演变的模型结合在一起，以量化高度爱情铁的元素的传递，其在地幔中的分布以及后期获得的材料的总质量。这些结果使人们对Hadean地球表面环境有了更多的了解。此外，短期影响动力学与长期地幔动态之间的联系可能会揭示地幔中异常的起源（例如大型低剪切速度提供者，这些提供商是深壁板上最重要的异常），地幔羽毛的动力学，以及地震磁场的历史。该项目还为研究生的跨学科培训提供了支持，西南研究所将在耶鲁大学举办1-2个地球物理专业的专业，以及一系列可视化的电影，这些电影可视化行星对教育的影响和地幔动态。地球形成月球形成的巨型撞击（称为“晚期积聚”）的剩下的行星持久轰炸得到了月球碎屑记录的支持，并需要在当今的炉灶中解释高度sideophile元素（HSES）的丰富性以及高度的金发比例。最近，基于具有平滑粒子流体动力学（SPH）的影响模拟，已建议晚期获得的质量比以前想象的高两到五倍，因为大部分HSE的大分分化层的金属核心（在其中大部分HSE）居住的金属核心没有有效地混入地幔中。对后期接受的质量的这种向上的修订可以极大地改变我们对Hadean Earth的理解。但是，基于SPH模拟的建议仍然是临时的，因为未纳入长期地幔动态引起的重要并发症。这是HSE的交付，其在地幔中的分布以及后期积聚的总质量仍然是宽阔的问题，对Hadean地球表面环境产生了重要影响。该项目旨在实现以下两个主要目标：（1）通过重新评估包括碎片化物理学在内的SPH模拟，量化分化行星核心的命运，以及通过进行系统的金属混合模拟来了解碎片金属斑点的长期命运。 The primary goal of this project is to determine the absolute scale of planetéesimal impact history, but achieving this goal will also help to address a wide range of important questions, from the habitability of the early Earth to the origin of deep geochemical reserves.This award reflects NSF's statutory mission and has been deemed precious of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.