德国航空航天中心A. Broquet团队通过冰川均衡调整揭示了火星的内部粘度结构。相关论文于2025年2月26日发表在《自然》杂志上。

研究冰川均衡调整一直是破译地球内部粘度结构的标准方法，但由于缺乏观测数据，这种方法很少应用于其他行星。火星的北极帽是唯一一个有数百万年历史的地表特征，可在这个星球上引起可测量的地表变形，从而为其目前的内部粘度结构提供线索。

研究组通过结合热演化模型、粘弹性变形计算和雷达观测来研究这个冰盖的定位。他们表明，北部地区的向下运动是持续的，可以通过分析时变重力场和美国宇航局的洞察号地震矩率来约束。仅适用于当前粘度较高的型号（深度大于500时为2-6×10²² Pa s km）、放射性元素的强烈地幔耗竭（超过90%）和厚的平均地壳（厚度超过40km）与雷达看到的极冠下可忽略的挠曲是一致的。北部岩石圈必须每年变形小于0.13毫米，地震效率小于0.3，以分别满足重力和地震约束。该模型表明，北极帽形成于过去的170-1200万年，冰川均衡调整可能会受到未来火星重力恢复任务的进一步限制。

附：英文原文

Title: Glacial isostatic adjustment reveals Mars’s interior viscosity structure

Author: Broquet, A., Plesa, A.-C., Klemann, V., Root, B. C., Genova, A., Wieczorek, M. A., Knapmeyer, M., Andrews-Hanna, J. C., Breuer, D.

Issue&Volume: 2025-02-26

Abstract: Investigating glacial isostatic adjustment has been the standard method to decipher Earth’s interior viscosity structure1,2, but such an approach has been rarely applied to other planets because of a lack of observational data3,4. The north polar cap of Mars is the only millions-of-years-old surface feature that can induce measurable surface deformation on this planet, thereby holding clues to its present-day internal viscosity structure5,6. Here we investigate the emplacement of this ice cap by combining thermal evolution models7, viscoelastic deformation calculations8 and radar observations6. We show that downward motion of the northern regions is ongoing and can be constrained by analyses of the time-variable gravity field9 and NASA’s InSight seismic moment rate10. Only models with present-day high viscosities (2–6×1022Pas for depths greater than 500km), strong mantle depletion in radiogenic elements (more than 90%) and thick average crusts (thicker than 40km) are consistent with the negligible flexure beneath the polar cap seen by radars. The northern lithosphere must deform at less than 0.13mm per year and have a seismic efficiency less than 0.3 to satisfy gravity and seismic constraints, respectively. Our models show that the north polar cap formed over the last 1.7–12.0Myr and that glacial isostatic adjustment can be further constrained by future gravity recovery missions to Mars11,12.

DOI: 10.1038/s41586-024-08565-9

Source: https://www.nature.com/articles/s41586-024-08565-9