12/31/2023 0 Comments Enceladus tiger stripes tidal heating![]() “One of the challenges of Enceladus is, if you can make fractures at the south pole with low stress, you should make fractures at the north pole with the same stress,” said first author Alyssa Rhoden, a planetary scientist at the Southwest Research Institute in Colorado. The new study considers the breaking point of the ice itself. Those studies focused on what happened when gravitational tugs on the moon were at their strongest. But previous studies have failed to simulate the formation of cracks that resemble the tiger stripes. Observations from Cassini revealed that the moon’s ice is thicker around the equator and thinner at the poles, especially the southern pole. Geological evidence for solid-state convection in Europa’s ice shell.The idea of thinner ice around the southern pole is certainly not new. ![]() Superplastic deformation of ice: Experimental observations. Diapir-induced reorientation of Saturn’s moon Enceladus. Modeling of the thermal behaviour and of the chemical differentiation of cometary nuclei. Compsition and physical properties of Enceladus’ surface. Vaporization of comet nuclei: light curves and life times. Stability and exchange of subsurface ice on Mars. The stability of ground ice in the equatorial region of Mars. Temperature evolution and vapour pressure build-up in porous ices. Viscoelastic models of tidal heating on Enceladus. Tectonic processes on Europa: tidal stresses, mechanical response and visible features. Patterns of fracture and tidal stresses on Europa. Strike-slip faults on Europa: global shear patterns driven by tidal stress. Subsurface oceans on Europa and Callisto: constraints from Galileo magnetometer observations. Distribution of strike-slip faults on Europa. Eruptions arising from tidally controlled periodic openings of rifts on Enceladus. A shear heating origin for ridges on Triton. Thermal consequences of strike-slip motion on Europa. Monte Carlo simulations of the water vapor plumes on Enceladus. Cassini ion and neutral mass spectrometer: Enceladus plume composition and structure. A clathrate reservoir hypothesis for Enceladus’ south polar plume. Cassini dust measurements at Enceladus and implications for the origin of the E ring. ![]() Cassini encounters Enceladus: background and the discovery of a south polar hot spot. ![]() Cassini observes the active south pole of Enceladus. We predict that the tiger-stripe regions with highest relative temperatures will be the lower-latitude branch of Damascus, Cairo around 60° W longitude and Alexandria around 150° W longitude. The tidal displacements required imply a Love number of h 2 > 0.01, suggesting that the ice shell is decoupled from the silicate interior by a subsurface ocean. ![]() The ice shell thickness needed to produce the observed heat flux is at least 5 km. Vapour produced by this heating may escape as plumes through cracks reopened by the tidal stresses 10. Here we show that the most likely explanation for the heat 2 and vapour production 6, 7 is shear heating by tidally driven lateral (strike-slip) fault motion 1, 8, 9 with displacement of ∼0.5 m over a tidal period. Neither model addresses how delivery of internal heat to the near-surface is sustained. The plume characteristics 1 and local high heat flux 2 have been ascribed either to the presence of liquid water within a few tens of metres of the surface 1, or the decomposition of clathrates 5. Enceladus, a small icy satellite of Saturn, has active plumes jetting from localized fractures (‘tiger stripes’) within an area of high heat flux near the south pole 1, 2, 3, 4. ![]()
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