CAREER: Volatiles in the Deep Earth: Insights From Theory and Experiments

地球是太阳系中唯一具备适宜居住条件的行星。使生命成为可能的一个关键因素是地球表面巨大的水库。然而，在地质年代尺度上，地球内部的岩石在维持地表液态水方面起着重要作用。液态水促进了地表岩石和矿物的风化，在这个过程中，产生了粘土和其他含水矿物相等矿物质，这些矿物质可以将液态水锁在它们的晶体结构中。这些含水矿物是在地表条件下储存水的最终水槽。如果风化过程不受阻碍地继续下去，地球表面所有的液态水都可能在几十亿年的时间尺度内储存在结晶的含水矿物中。地球岩石内部的地幔对流过程有助于通过脱水和随后的火山作用将储存在矿物质中的水循环回地表。深层的水在降低构成地幔的岩石的熔化温度方面起着重要作用。水也会以氢缺陷的形式加入地幔矿物中，影响它们的弹性和运输特性，包括流变性和黏性。这反过来又促进了地球上的地幔对流过程。由于水在地球深部过程中的重要性，限制水如何被输送到地球内部并确定地球岩石内部储存了多少水是很重要的。这个教师早期职业发展（Career）奖旨在通过整合研究、培训和指导STEM领域的下一代科学家和教育工作者，并使他们意识到固体地球研究对社会的重要性，来解决这些基本问题。通过佛罗里达州立大学本科研究机会计划（UROP）的本科生和通过青年学者计划（YSP）的高中生将参与这项研究。PI还将向代表性不足的学区的学生提供帮助，包括佛罗里达州的利昂县、加兹登县、杰斐逊县和汉密尔顿县以及佐治亚州的托马斯县。首席研究员（PI）将参加由挑战者学习中心主办的教育和推广活动。PI和他的团队将在国际会议上展示这个项目的成果，包括秋季美国地球物理联盟（AGU）会议。他们还将参加由NSF赞助的和由NSF资助的社区驱动的研讨会和会议。本研究的主要主题是探讨含氢矿物相的高压和温度物理性质。特别地，PI将使用实验和理论方法相结合的方法来研究氢的行为，以及它如何影响地球内部条件下矿物的弹性和传输特性，如扩散和导电性。含水矿物的性质将利用振动光谱、散射和衍射方法在国内和国际设施进行探索。利用共振超声光谱法研究含氢矿物的高温弹性。实验结果将用第一性原理模拟加以补充。弹性和输运性质的约束将与地球物理观测相关联，以便更好地约束水进入地球的输运。地球的内部以及地球深处水库的大小。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The Earth is the only planet in the solar system that has the right conditions for habitability. A key ingredient that makes life possible is a vast reservoir of water on the Earth's surface. However, the rocky interior of the Earth plays an important role in sustaining this surface liquid water over geological time scales. Liquid water facilitates weathering of surface rocks and minerals, and in the process, produces minerals such as clays and other hydrous mineral phases that can lock up the liquid water in their crystal structure. These hydrous minerals are the ultimate sinks for storing water at surficial conditions. If the weathering processes were to continue unhindered, all the liquid water on the Earth's surface could be potentially stored in the crystalline hydrous minerals in a time scale of a few billion years. The process of mantle convection in the rocky interior of the Earth helps in circulating this water stored in minerals back to the surface through dehydration and subsequent volcanism. Water at depth plays an important role in reducing the melting temperature of the rocks constituting the mantle. Water also gets incorporated as hydrogen defects in mantle minerals and affects their elastic and transport properties, including rheology and viscosity. This in turn facilitates mantle convection process in the Earth. Owing to the importance of water in the deep Earth processes, it is important to constrain how water is transported in to the Earth's interior and to determine how much water is stored in the rocky interior of the Earth. This Faculty Early Career Development (CAREER) award aims to address these fundamental questions by integrating research, training, and mentoring of the next generation of scientists and educators in the STEM fields and by making them aware of the importance of Solid Earth research for society. Undergraduate students through the Florida State University's Undergraduate Research Opportunity Program (UROP) and high school students through the Young Scholar Program (YSP) will be involved in this research. The PI will also reach out to school students from underrepresented school districts, including Leon, Gadsden, Jefferson, and Hamilton counties in Florida and Thomas County in Georgia. The principal investigator (PI) will participate in educational and outreach activities hosted by the Challenger Learning Center. The PI and his team will present the outcomes from this project at international conferences, including the Fall American Geophysical Union (AGU) meeting. They will also participate in NSF-sponsored and community-driven workshops and conferences funded by NSF.The overarching theme of this study will be to explore the high-pressure and temperature physical properties of hydrogen bearing mineral phases. In particular, the PI will use a combination of experiments and theoretical methods to examine the behavior of hydrogen and how it influences- elastic and transport properties such as diffusion and electrical conductivity of minerals at conditions relevant to the Earth's interior. The properties of hydrous minerals will be explored using vibrational spectroscopy, scattering and diffraction methods at both in house and international facilities. High-temperature elasticity of hydrogen bearing minerals will be examined using Resonant Ultrasound Spectroscopy. The experimental findings will be supplemented with first principles simulations. The constraints on elasticity and transport properties will be correlated with geophysical observations to put better constraints on the transport of water into the Earth?s interior and also the size of the water reservoir in the deep 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.