Enceladus' Tiger Stripes as Frictional Faults: Effect on Stress and Heat Production

Sládková, Kateřina; Souček, Ondřej; Běhounková, M.

doi:10.1029/2021gl094849

Cited by 11 publications

(30 citation statements)

References 45 publications

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“…(2017), and Sládková et al. (2021) and those described in this work relates to respective formulations for weak zones. Souček et al.…”

Section: Methodsmentioning

confidence: 75%

“…(2017), and Sládková et al. (2021) also focus on the implications of deformation for tidal heating, while we focus here on the inference of shell structural parameters in the presence of structural heterogeneities. Finally, our models additionally consider the effect of fault zones beyond the Tiger Stripes and thereby identify the extent to which other major structural heterogeneities (e.g., chasma and circum‐tectonic boundaries) may affect diurnal deformation patterns at Enceladus.…”

Section: Methodsmentioning

confidence: 99%

“…Deformation driven by the presence of frictionless faults (i.e., 2D interfaces) is distinct from that arising from crustal weak zones (i.e., finite‐width 3D volumes) in models. Water‐filled fault interfaces subject to effective hydrostatic normal stresses that exceed tidally driven stresses will resist extensional deformation in a manner similar to that of the surrounding elastic medium (see Text S1.1.1.4 in Supporting Information ; Sládková et al., 2021; Rovira‐Navarro et al., 2022). By contrast, 3D volumes that contain weakened material will exhibit less resistance to normal stresses than the surrounding elastic medium due to a locally reduced elastic Young's modulus (i.e., which is sensitive to G WZ for our formulation for weak zones; see also Segall, 2010).…”

Section: Methodsmentioning

confidence: 99%

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Inferring the Mean Thickness of the Outer Ice Shell of Enceladus From Diurnal Crustal Deformation

et al. 2023

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The thickness of the outer ice shell plays an important role in several geodynamical processes at ocean worlds. Here, we show that observations of tidally driven diurnal surface displacements can constrain the mean ice shell thickness, d∼ice ${\tilde{d}}_{\mathit{ice}}$. Such estimates are sensitive to any significant structural features that break spherical symmetry such as faults and lateral variation in ice shell thickness and structure. We develop a finite‐element model of Enceladus to calculate diurnal tidal displacements for a range of d∼ice ${\tilde{d}}_{\mathit{ice}}$ values in the presence of such structural heterogeneities. Consistent with results from prior studies, we find that the presence of variations in ice shell thickness can significantly amplify deformation in thinned regions. If major faults are also activated by tidal forcing—such as Tiger Stripes on Enceladus—their characteristic surface displacement patterns could easily be measured using modern geodetic methods. Within the family of Enceladus models explored, estimates of d∼ice ${\tilde{d}}_{\mathit{ice}}$ that assume spherical symmetry a priori can deviate from the true value by as much as ∼41% when structural heterogeneities are present. Additionally, we show that crustal heterogeneities near the South Pole produce differences of up to 35% between Love numbers evaluated at different spherical harmonic orders. A ∼41% range in estimates of d∼ice ${\tilde{d}}_{\mathit{ice}}$ from Love numbers is smaller than that found with approaches relying on static gravity and topography (∼250%) or analyzing diurnal libration amplitudes (∼85%) to infer d∼ice ${\tilde{d}}_{\mathit{ice}}$ at Enceladus. As such, we find that analysis of diurnal tidal deformation is a relatively robust approach to inferring mean crustal thickness.

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“…(2017), and Sládková et al. (2021) and those described in this work relates to respective formulations for weak zones. Souček et al.…”

Section: Methodsmentioning

confidence: 75%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Inferring the Mean Thickness of the Outer Ice Shell of Enceladus From Diurnal Crustal Deformation

et al. 2023

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“…Enceladus' ice shell is most likely brittle and conductive, limiting the amount of heat that can be dissipated within it to about 1 GW (Beuthe, 2019 ; Souček et al., 2019 ). Frictional heating along Enceladus' tiger stripes can contribute an additional 0.1–1 GW of energy dissipation (Pleiner Sládková et al., 2021 ), but, overall, tidal heating in the ice shell can only account for roughly 10% of the observed SPT thermal output. Ocean tides have been proposed as an additional heating mechanism (Tyler, 2011 ), but they only become important if Enceladus has an orbital obliquity two orders of magnitude higher than the expected value (Chen & Nimmo, 2011 ); or the ocean is unrealistically thin, radially stratified or turbulent (Chen et al., 2014 ; Hay & Matsuyama, 2019 ; Matsuyama, 2014 ; Rekier et al., 2019 ; Rovira‐Navarro et al., 2019 , 2020 ; Tyler, 2020 ; Wilson & Kerswell, 2018 ).…”

Section: Introductionmentioning

confidence: 99%

The Tides of Enceladus' Porous Core

et al. 2022

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The inferred density of Enceladus' core, together with evidence of hydrothermal activity within the moon, suggests that the core is porous. Tidal dissipation in an unconsolidated core has been proposed as the main source of Enceladus' geological activity. However, the tidal response of its core has generally been modeled assuming it behaves viscoelastically rather than poroviscoelastically. In this work, we analyze the poroviscoelastic response to better constrain the distribution of tidal dissipation within Enceladus. A poroviscoelastic body has a different tidal response than a viscoelastic one; pressure within the pores alters the stress field and induces a Darcian porous flow. This flow represents an additional pathway for energy dissipation. Using Biot's theory of poroviscoelasticity, we develop a new framework to obtain the tidal response of a spherically symmetric, self‐gravitating moon with porous layers and apply it to Enceladus. We show that the boundary conditions at the interface of the core and overlying ocean play a key role in the tidal response. The ocean hinders the development of a large‐amplitude Darcian flow, making negligible the Darcian contribution to the dissipation budget. We therefore infer that Enceladus' core can be the source of its geological activity only if it has a low rigidity and a very low viscosity. A future mission to Enceladus could test this hypothesis by measuring the phase lags of tidally induced changes of gravitational potential and surface displacements.

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“…Nevertheless, we acknowledge that in taking this approach, some processes and properties are not incorporated. For instance, lateral variations in ice shell thickness and physical properties can significantly affect the amount and distribution of tidal heating (Beuthe, 2013; Čadek et al., 2019; Pleiner Sládková et al., 2021; Souček et al., 2019).…”

Section: Methodsmentioning

confidence: 99%

Cooling Crusts Create Concomitant Cryovolcanic Cracks

Rudolph

Manga

Walker

et al. 2022

Geophysical Research Letters

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The orbital and internal evolution of the ice‐covered ocean worlds orbiting Jupiter and Saturn are coupled, leading to time‐varying thicknesses of their ice shells. As the ice thickens and thins, thermal stresses in the ice shell and pressure in the underlying ocean will change, promoting and hindering fracturing of the ice shell. We identify when and at what depth cracks initiate and whether they can penetrate the entire ice shell. For an ice tensile strength of 3 MPa, cracks do not penetrate the ice shell of Europa. On Enceladus, time‐averaged ice shell thickness of less than 15 km and variations in tidal dissipation of more than 15% over approximately 100 Myr eccentricity cycles cause cracks to cross the ice shell and permit eruptions from the ocean. Ocean overpressure is never large enough to extrude water onto the surface, suggesting that eruptions on Enceladus are sustained by decompression boiling.

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Enceladus' Tiger Stripes as Frictional Faults: Effect on Stress and Heat Production

Cited by 11 publications

References 45 publications

Inferring the Mean Thickness of the Outer Ice Shell of Enceladus From Diurnal Crustal Deformation

Inferring the Mean Thickness of the Outer Ice Shell of Enceladus From Diurnal Crustal Deformation

The Tides of Enceladus' Porous Core

Cooling Crusts Create Concomitant Cryovolcanic Cracks

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