Shock Wave Studies of Liquids in Earth's Core and Mantle

该奖项将为加州理工大学冲击波实验室提供持续支持，使其能够在与地球最深处的条件相匹配的条件下测量硅酸盐和金属液体的物理性质。这些信息对于从成分、温度、热流和随时间的演化来解释对下地幔和地核的地球物理观测是至关重要的。它还允许将关于早期熔融地球(即原始岩浆海洋)的推测发展成详细的理论。冲击压缩是唯一一种可以在这种极端条件下同时测量液体密度、压力、温度、能量和声速的实验方法。作为这项研究的一部分，该团队将进行实验开发，以实现比以前可能的更高的初始预热温度，从而能够直接研究与原始岩浆海洋和下地幔岩石学最相关的高熔点液体成分。实验和科学议程包括：1)以冲击温度测量技术的进展为基础，观察受冲击的硅酸盐液体的温度，限制它们在较低地幔压力下的热容量，从而完善我们在压力-温度-密度-能量空间描述它们的状态方程的能力；2)进一步开发新的方法，以获得比以前更高的初始预热温度，从而能够研究与早期岩浆海洋和下地幔岩石学最相关的超镁铁质液体成分的状态方程；3)开始测量铁液合金沿实际外核温度分布的声速和密度，以便使外核内声速随深度的明确观测梯度成为外核成分的新的和关键的约束。

This award will provide continued support for the Caltech shock wave laboratory to enable the measurement of physical properties of silicate and metallic liquids under conditions matching those in the deepest parts of the Earth. This information is critical to interpreting geophysical observations of the lower mantle and core in terms of composition, temperature, heat flow, and evolution over time. It also allows speculative ideas about an early molten earth (i.e., primordial magma ocean) to be developed into detailed theories. Shock compression is the only experimental method that can simultaneously measure density, pressure, temperature, energy, and sound speed of liquids at such extreme conditions. As part of this study, the team will undertake experimental developments to achieve much higher initial pre-heating temperatures than were previously possible, enabling the direct study of high-melting point liquid compositions most relevant to the primordial magma ocean and lower mantle petrology. The experimental and science agenda includes: 1) building on advances in shock temperature measurement techniques to look at temperatures of shocked silicate liquids, constraining their heat capacity at lower mantle pressures and thereby completing our ability to describe their equation of state in pressure-temperature-density-energy space; 2) furthering the development of new methods to achieve much higher initial pre-heating temperatures than were previously possible to enable the study of the equation of state of ultramafic liquid compositions most relevant to the early magma ocean and lower mantle petrology; and 3) initiating measurements of the sound speeds and densities of liquid iron alloys along actual outer core temperature profiles in order to make the well-defined observed gradient in sound speed with depth in the outer core a new and critical constraint on outer core composition.