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Dissipation of tidal energy is expected to generate seismicity on icy‐ocean worlds; however, the distribution and timing of this seismic activity throughout an orbital cycle is not known. We used new observations from an icy‐ocean‐world analog environment on Earth to examine the relationship between tidally driven tensile stress and seismic activity within an ice shell. We investigated a pair of rifts within Antarctica's Ross Ice Shelf which are tidally stressed in a manner analogous to the orbital cycle of tidal stress experienced by Enceladus' Tiger Stripe Fractures. We found that seismic activity at the Antarctic rifts is sensitive to both the amplitude and the rate of tensile stress across the rifts. We combined these findings with calculated stress values along Enceladus' Tiger Stripe Fractures to predict seismic‐activity levels expected along the ice‐shell fractures. We predict a peak in seismicity along the four Tiger Stripe Fractures when Enceladus is 90°–120° past pericenter in its orbit around Saturn, at which point tensile stresses would reach ∼2/3 of their maximum value. We also used the magnitude distribution of icequakes along Antarctic rifts to investigate implications for the likely size of stick‐slip rupture patches along icy faults on Enceladus. Our findings predict that the Tiger Stripe Fractures should produce sustained, low‐magnitude seismic events that involve rupture along discrete portions of each fracture's total length. We predict that seismicity would fall to 50% of peak levels when stresses across the Tiger Stripe Fractures are dominantly compressional. Plain Language Summary: Saturn's moon Enceladus is covered in ice which contains many long fractures or rifts, including four fractures called the Tiger Stripes. As Enceladus orbits Saturn, tidal forces cause the Tiger Stripe Fractures to erupt tall geysers of water vapor. This suggests that there is liquid water somewhere beneath Enceladus' icy surface and that there must be motion along the fractures. We expect that this motion should generate icequakes, similar to earthquakes on Earth. In this study, we built a model to predict where and when icequakes occur along the Tiger Stripe Fractures, using what we know about ice in Antarctica. We use a large floating expanse of solid ice, the Ross Ice Shelf, which contains fractures that are similar to the Tiger Stripe Fractures. We investigate Antarctic icequakes and find that the majority of icequakes occur during falling tide, when the rifts are being stretched open. We predict that the majority of icequakes along the Tiger Stripe Fractures occur around 100° into Enceladus' orbit and that these icequakes are very small, but numerous. Our results are valuable to future landed missions to Enceladus or another icy‐ocean world, where icequakes will help us understand what lies beneath the ice. Key Points: We predict significant seismicity along all four Tiger Stripe Fractures on Enceladus, with peak seismic activity ∼100° past pericenterWe find that rift seismicity is correlated with both applied tensile stress and tensile‐stress (stretching) rateGutenberg–Richter b‐value estimates for icequakes at studied rifts are ≥1.2, suggesting that b‐values >1 are appropriate for icy shells [ABSTRACT FROM AUTHOR]

Abstract: To explain the formation of surface features on Europa, Enceladus, and other satellites, many authors have postulated the spatial localization of tidal heating within convective plumes. However, the concept that enhanced tidal heating can occur within a convective plume has not been rigorously tested. Most models of this phenomenon adopt a tidal heating with a temperature-dependence derived for an incompressible, homogeneous (zero-dimensional) Maxwell material, but it is unclear whether this formulation is relevant to the heterogeneous situation of a warm plume surrounded by cold ice. To determine whether concentrated dissipation can occur in convective plumes, we develop a two-dimensional model to compute the volumetric dissipation rate for an idealized, vertically oriented, isolated convective plume obeying a Maxwellian viscoelastic compressible rheology. We apply the model to the Europa and Enceladus ice shells, and we investigate the consequences for partial melting and resurfacing processes on these bodies. We find that the tidal heating is strongly temperature dependent in a convective ice plume and could produce elevated temperatures and local partial melting in the ice shells of Europa and Enceladus. Our calculation provides the first quantitative verification of the hypothesis by Sotin et al. [Sotin, C., Head, J.W., Tobie, G., 2002. Geophys. Res. Lett. 29. 74-1] and others that the tidal dissipation rate is a strong function of temperature inside a convective plume. On Europa, such localized heating could help allow the formation of domes and chaos terrains by convection. On Enceladus, localized tidal heating in a thermal plume could explain the concentrated activity at the south pole and its associated heat transport of 2–7 GW. [Copyright &y& Elsevier]

Abstract: The composition and abundance of volatile gases observed in the jets emanating from fissures near the south pole of Saturn''s moon Enceladus are strongly indicative of outgassing from clathrate hydrates which formed as a result of hydrothermal activity rather than nebula condensation. I suggest that fluids must be able to permeate the ice shell, extensively metasomatising the mantle by emplacement of clathrates along fractures and grain boundaries, which subsequently are entrained in rising cryomagmas as xenoliths. These are carried upwards to the point where they dissociate, releasing their gas load into the magma and promoting the vigorous ice fountaining observed—a direct analogue of terrestrial basaltic fire fountains caused by volatile exsolution. This clathrate xenolith model can explain the measured volatile abundances, eruption velocities, the ice to vapour ratio in the plumes, and the vent temperatures. [Copyright &y& Elsevier]