Experimental Constraints On The Fatigue of Icy Satellite Lithospheres by Tidal Forces

TL;DR

This study experimentally tests whether icy satellite lithospheres weaken due to fatigue from tidal stresses, finding no fatigue at tested conditions but suggesting other factors may contribute to their weakness.

Contribution

The paper provides laboratory evidence that water ice does not fatigue under certain conditions, challenging the hypothesis that tidal fatigue weakens icy satellite lithospheres.

Findings

Ice is not susceptible to fatigue at 198 K and 233 K temperatures.

Brittle failure stress does not decrease with cyclic loading.

Colder temperatures and impurities may influence fatigue susceptibility.

Abstract

Fatigue can cause materials that undergo cyclic loading to experience brittle failure at much lower stresses than under monotonic loading. We propose that the lithospheres of icy satellites could become fatigued and thus weakened by cyclical tidal stresses. To test this hypothesis, we performed a series of laboratory experiments to measure the fatigue of water ice at temperatures of $198$ K and $233$ K and at a loading frequency of $1$ Hz. We find that ice is \textit{not} susceptible to fatigue at our experimental conditions and that the brittle failure stress does not decrease with increasing number of loading cycles. Even though fatigue was not observed at our experimental conditions, colder temperatures, lower loading frequencies, and impurities in the ice shells of icy satellites may increase the likelihood of fatigue crack growth. We also explore other mechanisms that may explain the weak behavior of the lithospheres of some icy satellites.