Experimental Constraints on the Fatigue of Icy Satellite Lithospheres by Tidal Forces

Hammond, N. P.; Barr, A. C.; Cooper, R. F.; Caswell, T. E.; Hirth, Greg

doi:10.1002/2017je005464

Cited by 21 publications

(24 citation statements)

References 88 publications

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“…In addition, repetitive deformation, such as from cyclic tidal stresses, can severely weaken materials over time through the process of fatigue. The role of fatigue in fracturing icy satellites is currently being investigated [e.g., Hammond et al ., ]. Scale may also be a factor, as the strengths of both rock and sea ice are heavily dependent on the size of the sample [ Dempsey et al ., ; Durham and Stern , ].…”

Section: Methodsmentioning

confidence: 99%

The implications of tides on the Mimas ocean hypothesis

et al. 2017

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We investigate whether a present‐day global ocean within Mimas is compatible with the lack of tectonic activity on its surface by computing tidal stresses for ocean‐bearing interior structure models derived from observed librations. We find that, for the suite of compatible rheological models, peak surface tidal stresses caused by Mimas' high eccentricity would range from a factor of 2 smaller to an order of magnitude larger than those on tidally active Europa. Thermal stresses from a freezing ocean, or a past higher eccentricity, would enhance present‐day tidal stresses, exceeding the magnitudes associated with Europa's ubiquitous tidally driven fractures and, in some cases, the failure strength of ice in laboratory studies. Therefore, in order for Mimas to have an ocean, its ice shell cannot fail at the stress values implied for Europa. Furthermore, if Mimas' ocean is freezing out, the ice shell must also be able to withstand thermal stresses that could be an order of magnitude higher than the failure strength of laboratory ice samples. In light of these challenges, we consider an ocean‐free Mimas to be the most straightforward model, best supported by our tidal stress analysis.

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Section: Methodsmentioning

confidence: 99%

The implications of tides on the Mimas ocean hypothesis

et al. 2017

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“…where σ crit is the tensile failure limit for cold ice, which we take to be 1 MPa (e.g., 37 ) for intact ice or 100 kPa for previously weakened ice.…”

Section: Bending Stressesmentioning

confidence: 99%

Cascading parallel fractures on Enceladus

2019

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Active eruptions from the south polar region of Saturn's small (∼ 500 km diameter) moon Enceladus are concentrated along a series of lineaments known as the 'tiger stripes' 1,2 , thought to be partially open fissures that connect to the liquid water ocean beneath the ice shell 3,4 . Whereas aspects of the tiger stripes have been addressed in previous work, no study to date simultaneously explains why they should be located only at the south pole, why there are multiple approximately parallel and regularly spaced fractures, and what accounts for their spacing of ∼ 35 km. Here we propose that secular cooling and the resulting ice shell thickening and global tensile stresses 5,6 cause the first fracture to form at one of the poles, where the ice shell is thinnest due to tidal heating 7 . The tensile stresses are thereby partially relieved, preventing a similar failure at the opposite pole. We propose that subsequent activity then concentrates in the vicinity of the first fracture as the steadily erupted water ice loads the flanks of the open fissure, causing bending in the surrounding elastic plate and further tensile failure in bands parallel to the first fracture, leading to a cascading sequence of parallel fissures until the conditions no longer permit through-going fractures.

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“…Based on the growing count of planetary bodies containing some quantity of ammonia in contact with ice, additional efforts should be devoted to understanding the full range of rheological properties of the ice-ammonia system. For instance, ammonia at the grain scale could affect fatigue and failure stress within a relentlessly stressed icy moon [71]. Additional studies to characterize S-wave velocities and attenuation in this system are recommended.…”

Section: Applications To Icy Satellitesmentioning

confidence: 99%

Acoustic and Microstructural Properties of Partially Molten Samples in the Ice–Ammonia System

et al. 2019

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We measured the ultrasonic properties and microstructure of two-phase binary mixtures of the ice–ammonia partial melt system, which was selected based on its importance for numerous planetary bodies. The equilibrium microstructure of ice–ammonia melt was examined using a light microscope within a cold room. The measured median dihedral angle between the solid and melt at 256 K is approximately 63°, with a broad distribution of observed angles between 10° and 130°. P-wave velocities in the partially molten samples were measured as a function of temperature (177 < T(K) < 268) and composition (1–6.4 wt % NH3). Vp decreases approximately linearly with increasing temperature and melt fraction. We compare the results of this study to those of other potential binary systems by normalizing the datasets using a vertical lever (TL–TE) and articulating the potential effects on the mechanical behavior and transport capabilities of partially molten ice in icy satellites.

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Experimental Constraints on the Fatigue of Icy Satellite Lithospheres by Tidal Forces

Cited by 21 publications

References 88 publications

The implications of tides on the Mimas ocean hypothesis

The implications of tides on the Mimas ocean hypothesis

Cascading parallel fractures on Enceladus

Acoustic and Microstructural Properties of Partially Molten Samples in the Ice–Ammonia System

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