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The Growth of Europa's Icy Shell: Convection and Crystallization
Journal of Geophysical Research: Planets ( IF 4.8 ) Pub Date : 2021-03-09 , DOI: 10.1029/2020je006677
A. P. Green 1 , L. G. J. Montesi 2 , C. M. Cooper 1
Affiliation  

The thickness of Europa's icy shell, which controls its thermal and rheological structure, cannot currently be directly measured. However, it can be estimated through indirect methods, including geodynamic modeling. We simulate the crystallization of the ice shell from a liquid water ocean and its subsequent thermal equilibration in the presence of tidal heat. We evaluate the effects of solid‐state stagnant lid convection on the shell's thermal equilibrium thickness and shell formation timing. The thermal equilibrium thickness of the ice shell ranges from 5 to 30 km, depending on the imposed tidal flexure strain rate. The ice lithospheric thickness remains less than 8 km, independently of imposed tidal flexure strain rate, overall shell thickness, and surface temperature, suggesting the Europan ice lithospheric strength is globally uniform. Thermal convection significantly reduces the thermal equilibration time scale, with the Europan ice shell able to fully crystallize out from a liquid water ocean in less than 2 Myr. Heterogeneous thermal equilibrium thickness values across the satellite suggest that widespread crystallization and melting may occur at the base of the shell. Rapid melting and crystallization timing suggest that the young surface age of the Europan ice shell may be the result of rapid catastrophic whole‐shell melting and recrystallization entirely recycling the surface.

中文翻译:

欧罗巴冰冷外壳的生长:对流和结晶

欧罗巴冰冷外壳的厚度(控制其热和流变结构)目前无法直接测量。但是,可以通过包括地球动力学建模在内的间接方法进行估算。我们模拟了液态海洋中冰壳的结晶及其在潮汐热作用下的后续热平衡。我们评估了固态滞留对流对壳体热平衡厚度和壳体形成时间的影响。冰壳的热平衡厚度范围为5至30 km,具体取决于施加的潮汐挠曲应变率。与施加的潮汐挠曲应变率,总壳厚度和表面温度无关,冰岩石圈厚度仍小于8 km,这表明Europan冰岩石圈强度在全球范围内是一致的。热对流大大减少了热平衡时间,Europan冰壳能够在不到2 Myr的温度下从液态海洋中完全结晶出来。卫星上不同的热平衡厚度值表明,广泛的结晶和熔化可能发生在壳的底部。快速的融化和结晶时间表明,Europan冰壳的年轻表面年龄可能是灾难性的全壳快速融化和重结晶完全回收了表面的结果。卫星上不同的热平衡厚度值表明,广泛的结晶和熔化可能发生在壳的底部。快速的融化和结晶时间表明,Europan冰壳的年轻表面年龄可能是灾难性的全壳快速融化和重结晶完全回收了表面的结果。卫星上不同的热平衡厚度值表明,在壳的底部可能会发生广泛的结晶和熔化。快速的融化和结晶时间表明,Europan冰壳的年轻表面年龄可能是灾难性的全壳快速融化和重结晶完全回收了表面的结果。
更新日期:2021-04-08
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