CAREER: Visualizing Earth's Core-Mantle Interactions using Nanoscale X-ray Tomography

核心形成是地球和其他行星体历史上的一个关键事件。已经提出了许多关于核和地幔如何分离和相互作用的机制；然而，它们的有效性必须通过直接的实验模拟来测试，这在以前是不可能的。研究人员一直在开发一种新的方法，使用纳米级X射线计算机断层扫描(NanXCT)在高压下捕获材料的图像。有人提议使用这种新的X射线成像技术来研究在超高压和温度下微量的铁和硅酸盐矿物是如何相互作用的，以揭示地球岩石地幔与其富含铁的核心的分离。由于一张图片胜过千言万语，学生和更广泛的公众也很容易获得X射线成像研究，以3D电影格式呈现的地球核心和地幔材料如何相互作用的可视化为教育和推广提供了一个有吸引力的工具。在加利福尼亚州，将地球科学作为课程的一部分只要求在六年级教授，因此这是年轻女孩培养对科学的兴趣的关键时刻，也是让所有学生参与地球科学领域的独特机会。主要的外展活动之一是通过设计将X射线断层扫描与地震断层扫描相联系的活动来与一所女子中学建立工作伙伴关系，学生们已经通过边际计划接触到了地震断层扫描。这项职业计划的目标是提高我们对地球深部的了解，重点是开发高分辨率纳米级X射线计算机层析成像(NanXCT)，以可视化地球核-地幔相互作用。NanoXCT代表了一种功能强大的非破坏性、纳米级分辨率的3D探测器，当与钻石砧座单元结合使用时，可以对在极端条件下合成的多种矿物和非晶相(包括熔体)进行成像。NanoXCT将用于确定铁水和固体硅酸盐矿物的结构和形状，因为它们对地球深处发现的同样强烈的压力和温度做出反应，将为潜在的核心形成机制提供测试。对可能存在于核-地幔边界上方的层中的假定部分熔体形成的熔腔和通道的形状的测量将提供对这一复杂区域的洞察。由于增加了第三维度、更高的分辨率以及延伸到非常高的压力和温度，NanXCT为地球科学以外的许多领域提供了令人兴奋的新成像机会。

Core formation represents a pivotal event in the history of the Earth and other planetary bodies. A number of mechanisms have been proposed for how the core and mantle separate and interact; their validity, however, must be tested by direct experimental simulations which have not been previously possible. The investigator has been developing a new method to use nanoscale X-ray computed tomography (nanoXCT) to capture images of materials at high pressure. It is proposed to use this novel x-ray imaging technique to study how minute amounts of iron and silicate minerals interact at ultrahigh pressures and temperatures in order to shed light on the separation of Earth's rocky mantle from its iron-rich core. As a picture is worth a thousand words, x-ray imaging research is also easily accessible to students and to the broader public, and the visualization of how Earth's core and mantle materials interact presented in 3D movie format provides an attractive tool for education and outreach. In California, teaching Earth Science as part of the curriculum is only required in the 6th grade, so this is a critical time for young girls to develop an interest in science and a unique opportunity to engage all students in the fields of Geosciences. One of the main outreach activities is to develop a working partnership with a Girls' Middle School through the design of activities that will relate x-ray tomography to seismic tomography, which the students will already have been exposed to through the MARGINS program. The goal of this CAREER proposal is to improve our understanding of the Earth's deep interior focusing on developing high resolution nanoscale x-ray computed tomography (nanoXCT) to visualize Earth's core-mantle interactions. NanoXCT represents a powerful non-destructive, nanoscale resolution 3D probe which when coupled with a diamond anvil cell enables imaging of multiple minerals and amorphous phases (including melts) which are synthesized under extreme conditions. NanoXCT will be used to determine the texture and shape of molten iron and solid silicate minerals as they respond to the same intense pressures and temperatures found deep in the Earth will provide a test for potential mechanisms of core formation. Measurements of the shape of the melt pockets and channels formed by the putative partial melt which may exist in the layer just above the core-mantle boundary will provide insight into this complex region. With the added third dimension, higher resolution, and extension to very high pressures and temperatures, nanoXCT provides exciting new imaging opportunities for many fields beyond Earth Sciences.