2023-04-14 アリゾナ大学
アリゾナ大学のMackenzie Mills博士課程学生が主導する研究チームは、氷の衛星表面がどのように進化するかを明らかにしました。NASAのEuropa Clipperミッションなどが今後の研究に重要な役割を果たすと期待されています。
＜関連情報＞
- https://news.arizona.edu/story/icy-moonquakes-surface-shaking-could-trigger-landslides
- https://www.sciencedirect.com/science/article/pii/S0019103523001112
月震をトリガーとする氷衛星の物質浪費プロセス Moonquake-triggered mass wasting processes on icy satellites
Mackenzie M. Mills, Robert T. Pappalardo, Mark P. Panning, Erin J. Leonard, Samuel M. Howell
Icarus Available online: 24 March 2023
DOI:https://doi.org/10.1016/j.icarus.2023.115534
Highlights
•Studied ridge populations on icy moons follow trends akin to normal faults.
•We model a moonquake magnitude range of 4.0–7.9, which may generate seismic accelerations exceeding satellite gravities.
•Seismicity-driven mass wasting may have generated some smooth materials (∼100 s–∼1000s m scale) present on icy satellites.
Abstract
Intense tectonism is evident on many outer solar system satellites with some surface regions exhibiting ridge-and-trough structures which have characteristics suggestive of normal faulting. In some cases, topographic lows between subparallel ridges are sites of smooth material displaying few craters. We consider whether such smooth material can be generated by mass wasting triggered from local seismic shaking. We hypothesize that debris would flow from topographic highs into lows, initially mobilized by moonquake-induced seismic shaking during formation of local tectonic ridges, covering and infilling older terrain. We analyze the feasibility of seismicity to trigger mass movements by measuring fault scarp dimensions to estimate quake moment magnitudes. The inferred magnitude range is 4.0–7.9, and we use numerical modeling to estimate seismic accelerations resulting from such quakes. This modeled magnitude range implies seismic accelerations that can exceed satellite gravitational accelerations, particularly near quake epicenters. Thus, seismic events could feasibly cause mass wasting of material to form some fine-scale smooth surfaces observed on at least three icy satellites: Ganymede, Europa, and Enceladus.
