2024-04-29 カリフォルニア工科大学(Caltech)
カリフォルニア工科大学の新研究では、これらの断層の動きを詳細にモデル化し、断層がストライクスリップ運動をしていることを示唆しています。この発見は、エンセラダスの翼の強度の変動や、生命を支える可能性のある条件の理解に寄与しています。
＜関連情報＞
- https://www.caltech.edu/about/news/enceladus-spills-its-guts-through-strikeslip-motion
- https://www.nature.com/articles/s41561-024-01418-0
エンケラドスでのジェット活動は、潮汐駆動によるトラの縞に沿った横ずれ運動と関連している Jet activity on Enceladus linked to tidally driven strike-slip motion along tiger stripes
Alexander Berne,Mark Simons,James T. Keane,Erin J. Leonard &Ryan S. Park
Nature Geoscience Published:29 April 2024
DOI:https://doi.org/10.1038/s41561-024-01418-0
Abstract
At Saturn’s moon Enceladus, jets along four distinct fractures called ‘tiger stripes’ erupt ice crystals into a broad plume above the South Pole. The tiger stripes experience variations in tidally driven shear and normal traction as Enceladus orbits Saturn. Here, we use numerical finite-element modelling of a spherical ice shell subjected to tidal forces to show that this traction may produce quasi-periodic strike-slip motion in the Enceladus crust with two peaks in activity during each orbit. We suggest that friction modulates the response of tiger stripes to driving stresses, such that tidal traction on the faults results in a difference in the magnitudes of peak strike slip and delays the first peak in fault motion following peak tidal stress. The simulated double-peaked and asymmetric strike-slip motion of the tiger stripes is consistent with diurnal variations in jet activity inferred from Cassini spacecraft images of plume brightness. The spatial distribution of strike-slip motion also matches Cassini infrared observations of heat flow. We hypothesize that strike-slip motion can extend transtensional bends (for example, pull-apart structures) along geometric irregularities over the tiger stripes and thus modulate jet activity. Tidally driven fault motion may also influence longer term tectonic evolution near the South Pole of the satellite.
