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Periodic Strike-Slip Motion Along Frictional Tiger Stripes Modulates Plume Output at Enceladus

Presentation #303.07 in the session Enceladus (Oral Presentation)

Published onOct 23, 2023
Periodic Strike-Slip Motion Along Frictional Tiger Stripes Modulates Plume Output at Enceladus

At Enceladus, jets along four distinct fractures (i.e., ‘Tiger Stripes’) erupt ice crystals into a broad plume above the South Pole. Repeated, high-resolution measurements of plume brightness from the Cassini Imaging Science Subsystem (ISS) indicate that jet output varies with a period equal to that of Enceladus’s orbit of 32.9 hrs. Tidally-driven normal displacement along fractures could modulate jet activity but require either viscous effects or fluid inertia to account for the ‘phase lag’ of ~ 5-6 hrs between maximal opening and observed peak activity at mean anomaly φ = 210°. Moreover, normal opening does not readily produce a second, smaller observed peak in activity near φ= 30°. Here, we use a 3D numerical model of tidal deformation to demonstrate that the Tiger Stripes exhibit periodic strike-slip motion with a temporal pattern that is highly correlated with observations of plume activity. Diurnally rotating shear tractions along the Tiger Stripes naturally produce peaks in left- and right- lateral motion near φ = 30° and 210°, respectively. Large variations in tidally-driven normal traction (~ 60 kPa) along interfaces reduce the amplitude of the peak in strike-slip motion at φ = 30° relative to that at φ = 210° for Tiger Stripes which exhibit Coulomb friction. The spatial distribution of mean strike slip motion along the Tiger Stripes is also consistent with observations of heat flow which show maximal activity along longer faults (i.e., Baghdad Sulcus) and near the center of each fracture. We conclude that periodic right- and left- stepping bend opening due to strike-slip motion along the Tiger Stripes could feasibly modulate Enceladus’s short-term activity and long-term tectonic evolution.

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