Grain-scale thermoelastic stresses and spatiotemporal temperature gradients on airless bodies, implications for rock breakdown.
Stephen A. Langer
Thermomechanical processes such as fatigue and shock have been suggested to cause and contribute to rock breakdown on Earth, and on other planetary bodies, particularly airless bodies in the inner solar system. In this study, we modeled grain-scale stresses induced by diurnal temperature variations on simple microstructures made of pyroxene and plagioclase on various solar system bodies. We found that a heterogeneous microstructure on the Moon experiences peak tensile stresses on the order of 100 MPa. The stresses induced are controlled by the coefficient of thermal expansion and Youngs modulus of the mineral constituents, and the average stress within the microstructure is determined by relative volume of each mineral. Amplification of stresses occurs at surface-parallel boundaries between adjacent mineral grains and at the tips of pore spaces. We also found that spatial and temporal temperature gradients do not correlate with high stresses, making them inappropriate proxies for investigating microcrack propagation. Although these results provide very strong evidence for the significance of thermomechanical processes on airless bodies, more work is needed to quantify crack propagation and rock breakdown rates. Understanding where in the solar system thermomechanical breakdown may occur has important implications for regolith production rates, surface ages and crater degradation rates, and landscape evolution over time.
Grain-scale thermoelastic stresses and spatiotemporal temperature gradients on airless bodies, implications for rock breakdown., Journal of Geophysical Research, [online], https://doi.org/10.1002/2014JE004729
(Accessed December 10, 2023)