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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Shock and post-shock temperatures in an ice-quartz mixture: implications for melting during planetary impact events
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Shock and post-shock temperatures in an ice-quartz mixture: implications for melting during planetary impact events

机译：冰-石英混合物中的冲击温度和震后温度：对行星撞击事件中融化的影响

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Melting of H2O ice during planetary impact events is a widespread phenomenon. On planetary surfaces, ice is often mixed with other materials; yet, at present, the partitioning of energy between the components of a shocked mixture is still an open question in the shock physics community. Knowledge of how much energy is partitioned into the ice component is necessary to predict and interpret a wide range of processes, including shock-induced melting and chemistry. In this work, we construct a conceptual framework for the thermodynamic pathways of the components in a shocked hydrodynamic mixture by defining three broad regimes based on the characteristic length scale of the mixture compared to the thickness of the shock front: (I) small length scale mixtures where pressure and temperature equilibrate immediately behind the shock front; (2) intermediate length scales where pressure but not thermal equilibration is achieved behind the shock front; and (3) long length scales where pressure equilibration requires multiple shock wave reflections. We conduct shock wave experiments, reaching pressures from 8 to 23 GPa, in an H2O ice-SiO2 quartz mixture in the intermediate length scale regime. In each experiment, all the parameters required to address the question of energy partitioning were determined: the shock velocity in the mixture, the shock front thickness, and the shock and post-shock temperatures of the H2O component. The measured pressure is in agreement with the bulk compressibility of the mixture. The shock and post-shock temperatures of the H2O component indicate that the ice was shocked close to the principal Hugoniot. Therefore, in the intermediate length scale regime, the partitioning of shock energy is defined initially by the Hugoniots of the components at the equilibrated pressure. We discuss energy partitioning in mixtures over the wide range of length and time scales encountered during planetary impact events and identify the current challenges in calculating the volume of melted ice. In some cases, the criteria for shock-induced melting of ice in a mixture are the same as for pure ice.
机译：行星撞击事件期间H2O冰的融化是一种普遍现象。在行星表面，冰经常与其他物质混合。然而，目前，在冲击混合物的各组分之间进行能量分配仍然是冲击物理学界的一个悬而未决的问题。要预测和解释各种过程，包括冲击引起的融化和化学过程，必须知道将多少能量分配到冰成分中。在这项工作中，我们根据与冲击前沿厚度相比的混合物特征长度尺度定义了三种宽泛的范围，从而定义了三种流体力学状态，从而为冲击流体混合物中的组分的热力学途径构建了概念框架：（I）小长度尺度压力和温度在冲击锋面后立即达到平衡的混合物; （2）中间长度标尺，在冲击前部后面达到压力而不达到热平衡; （3）长标尺，压力平衡需要多次冲击波反射。我们在中等长度范围内的H2O冰-SiO2石英混合物中进行了8至23 GPa压力的冲击波实验。在每个实验中，确定了解决能量分配问题所需的所有参数：混合物中的激波速度，激波前部厚度以及H2O组分的激波和激波后温度。测得的压力与混合物的整体可压缩性一致。 H2O组分的冲击温度和震后温度表明，冰在接近主要Hugoniot处被冲击。因此，在中等长度尺度范围内，冲击能量的分配最初是由平衡压力下各组分的Hugoniots定义的。我们讨论了在行星撞击事件期间遇到的各种长度和时间范围内的混合物中的能量分配，并确定了计算融冰量时当前面临的挑战。在某些情况下，混合物中冰引起的激振融化的标准与纯冰相同。

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