Geophysics of Iron in the Earth’s Core

地核中铁的地球物理学

• 批准号: 2049620
• 负责人: Wendy Mao
• 金额: $ 33.01万
• 依托单位: Stanford 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: 2021-02-01 至 2025-01-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2049620&HistoricalAwards=false
• 关键词: Geophysics; Iron; Earth; Core

Located nearly 3000 km below the crust, the Earth’s core is the most remote region within our planet. Mainly composed of iron, the core’s outer shell is liquid while its most inner part, the inner core, is solid. The core plays a central role in the planet’s geomagnetism, dynamic processes, and thermal evolution. Here, the team conducts laboratory experiments at the extreme pressures and temperatures prevailing in Earth’s deep interior. They measure the properties of the iron-rich materials that make up the core, e.g., their deformation mechanisms and viscosity. These properties can be dramatically altered at core conditions. The results give insight into why seismic waves travel at different speeds through different parts of the inner core. They constrain how the Earth’s magnetic field is generated and unveil its past evolution. These outcomes are valuable to many researchers studying deep Earth’s processes: mineral physicists, seismologists, and geodynamicists. The project promotes technical advances useful across disciplines, in geoscience and materials science, and in the industry. It also provides support for a female graduate student, training for undergraduate students, and outreach toward K-12 students and the public.The project aims at characterizing key rheological properties of iron and iron-rich compounds and alloys at the extreme conditions of the deep Earth. Two fundamental questions are addressed: (1) What causes inner-core seismic anisotropy? (2) How does viscous dissipation in the outer core influence the evolution of the geodynamo? To address the first question, the team characterizes the dominant deformation mechanisms and strength of solid iron at high pressures and temperatures. The lattice preferred orientation that develops during iron crystallization is also measured. The goal is to understand how the alignment of elastically anisotropic iron crystals may be acquired during solidification or subsequent deformation (or both). To this aim, the researchers carry out static compression experiments in resistive and laser-heated diamond anvil cells. They perform in situ X-ray imaging and diffraction measurements at national synchrotron facilities. Addressing the second question requires measuring iron viscosity at core conditions. While traditional measurements are limited to lower pressures, the team benefit from new technical developments; these enable a path toward measuring the viscosity of iron dynamically compressed to outer core conditions. Thus the team carries out dynamic compression experiments and use novel X-ray diffraction and imaging techniques at the Materials at Extreme Conditions instrument at the Linac Coherent Light Source (SLAC) and the National Ignition Facility at Lawrence Livermore National Laboratory. These experiments represent new opportunities to leverage the considerable resources and expertise available at national laboratories and apply them to better understand the Earth.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.

地核位于地壳下方近3000公里处，是地球上最偏远的地区。核芯的外壳主要由铁组成，是液体，而其最里面的部分，即内核，则是固体。地核在地球的地磁、动态过程和热演化中起着核心作用。在这里，该团队在地球深处普遍存在的极端压力和温度下进行实验室实验。它们测量组成核心的富铁材料的性质，例如，它们的变形机制和粘度。这些特性可以在核心条件下显著改变。这些结果揭示了为什么地震波在内核的不同部分以不同的速度传播。它们限制了地球磁场是如何产生的，并揭示了它过去的演化。这些结果对许多研究地球深部过程的研究人员是有价值的：矿物物理学家、地震学家和地球动力学家。该项目促进了跨学科、在地球科学和材料科学以及该行业中有用的技术进步。它还为一名女研究生提供支持，为本科生提供培训，并面向K-12学生和公众进行宣传。该项目旨在表征地球深处极端条件下铁和富铁化合物及合金的关键流变性。讨论了两个基本问题：(1)是什么导致了内核的地震各向异性？(2)外核的粘性耗散如何影响地球发电机的演化？为了解决第一个问题，研究小组描述了固态铁在高压和高温下的主要变形机制和强度。还测量了在铁结晶过程中形成的晶格择优取向。目标是了解如何在凝固或随后的变形(或两者)过程中获得弹性各向异性铁晶体的排列。为此，研究人员在电阻和激光加热的钻石砧座单元中进行了静态压缩实验。他们在国家同步加速器设施中进行现场X射线成像和衍射测量。解决第二个问题需要测量核心条件下的铁粘度。虽然传统的测量仅限于较低的压力，但该团队受益于新的技术发展；这些技术使测量动态压缩到外核条件下的铁的粘度成为可能。因此，该团队在直线加速器相干光源(SLAC)和劳伦斯利弗莫尔国家实验室的国家点火设施的极端条件下的材料仪器上进行了动态压缩实验，并使用了新颖的X射线衍射和成像技术。这些实验代表了利用国家实验室现有的大量资源和专业知识并将其应用于更好地了解地球的新机会。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Geomimicry—Liberating high-pressure research by encapsulation

• DOI: 10.1063/5.0126898
• 发表时间: 2022-11
• 期刊: Matter and Radiation at Extremes
• 影响因子: 5.1
• 作者: H. Mao;W. Mao

Ultrafast X-ray Diffraction Study of a Shock-Compressed Iron Meteorite above 100 GPa

100 GPa 以上冲击压缩铁陨石的超快 X 射线衍射研究

• DOI: 10.3390/min11060567
• 发表时间: 2021
• 期刊: Minerals
• 影响因子: 2.5
• 作者: Tecklenburg, Sabrina;Colina-Ruiz, Roberto;Hok, Sovanndara;Bolme, Cynthia;Galtier, Eric;Granados, Eduardo;Hashim, Akel;Lee, Hae Ja;Merkel, Sébastien;Morrow, Benjamin
• 通讯作者: Morrow, Benjamin

Noble gas incorporation into silicate glasses: implications for planetary volatile storage

稀有气体掺入硅酸盐玻璃：对行星挥发性储存的影响

• DOI: 10.7185/geochemlet.2105
• 发表时间: 2021
• 期刊: Geochemical Perspectives Letters
• 影响因子: 4.9
• 作者: Yang, H.;Gleason, A.E.;Tkachev, S.N.;Chen, B.;Jeanloz, R.;Mao, W.L.
• 通讯作者: Mao, W.L.