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

该奖项将支持加州理工学院冲击波实验室在与地球最深处相匹配的条件下测量岩石和金属液体特性的一项为期三年的努力。这些信息对于解释下地幔和地核的组成、温度、热流和随时间演变的地球物理观测至关重要。它还允许对早期熔融地球的推测发展成详细的理论。激波压缩是唯一能在如此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。本提案中的实验和科学议程是由关键技术进步推动的。一种封装技术的发展使我们能够将硅酸盐玻璃预热到熔点以上，而不会形成气泡，并密封在透明窗口后面，使我们能够观察受冲击液体的热辐射。在受冲击的岩浆中测量温度和声速，将使我们能够描述它们在任何所需压力和温度下的特性。同样，用于定制冲击和斜坡加载路径的梯度密度冲击器的开发，以及我们的预热能力和先进窗口材料的开发，使得沿着实际外岩心温度曲线测量液态铁合金的声速和密度成为可能。这一新颖的实验测量方法将使外核中声速随深度的明显梯度成为外核组成的一个新的关键约束条件。

This award will support a three-year effort in the Caltech shock wave laboratory to measure properties of rocky 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 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.The experimental and science agenda in this proposal is driven by key technical advances. Development of an encapsulation technique allowing us to pre-heat silicate glasses well above their melting point without formation of bubbles and in sealed behind a transparent window allows us to observe thermal radiation from the shocked liquid. Measurement of temperatures and sound speeds in shocked magmas will complete our ability to describe their properties at any desired pressure and temperature. Likewise, the development of graded density impactors for customized shock-and-ramp loading paths, together with our pre-heating capability and development of advanced window materials enabled measurement of the sound speeds and densities of liquid iron alloys along actual outer core temperature profiles. This novel experimental measurement will make the well-defined observed gradient in sound speed with depth in the outer core a new and critical constraint on outer core composition.