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Article Dans Une Revue Journal of Geophysical Research. Planets Année : 2019

Unraveling the mechanics of thermal stress weathering: rate-effects, size-effects, and scaling laws

Résumé

Thermal stress weathering is now recognized to be an active and significant geomorphological process on airless bodies. This study aims to understand the key factors governing thermal stresses in rocks on airless bodies through extensive numerical calculations and analytic analyses. Some of the key factors governing thermal stresses, are found to be the diurnal surface temperature variation, the second-order spatial gradient of the temperature field, the thermal skin depth, and the rock size of interest. Microscopic (grain-scale) thermal stresses are driven primarily by the amplitude of the magnitude of the maximum diurnal temperature variation at said depth. Macroscopic (rock-scale) thermal stresses are more complex, and their nature fundamentally depends on two length scales: the thermal skin depth and the rock size of interests. For rock sizes larger than the thermal skin depth, macroscopic thermal stresses are driven primarily by second (and higher) order spatial gradients of temperature. For rock sizes smaller than the thermal skin depth, macroscopic thermal stresses are primarily driven by the ratio of rock size to thermal skin depth with macroscopic thermal stresses being greatest when this ratio is 1/2. Additionally, scaling relations for diurnal surface temperature variation, time-rateof-change of surface temperature, as well as peak microscopic (grain-scale) and macroscopic (rock-scale) thermal stresses are derived to provide a more accessible modeling tool. These scaling relations are remarkably accurate when compared to both the numerical calculations as well as three-dimensional finite element calculations. The model formulation, results, and scaling relations provided here allow the estimation of diurnal temperatures and thermal stresses on rocks of various size and materials on airless bodies at any orbital distance with a broad spectrum of spin rates. Lastly, we postulate and confirm that there is a critical spin rate where macroscopic thermal stresses will be greatest.
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Dates et versions

hal-03053205 , version 1 (10-12-2020)

Identifiants

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Babak Ravaji, Víctor Alí-Lagoa, Marco Delbo, J. W Wilkerson. Unraveling the mechanics of thermal stress weathering: rate-effects, size-effects, and scaling laws. Journal of Geophysical Research. Planets, 2019, 124 (12), pp.3304-3328. ⟨10.1029/2019JE006019⟩. ⟨hal-03053205⟩
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