Rethinking Regolith Strength: Why Nonlinearity Matters on Small Bodies
- 1Université de Toulouse
Abstract
A widely used approach in planetary science to describe the strength and behavior of geological materials is the Mohr–Coulomb equation, yet it actually represents a linear approximation to a nonlinear failure envelope that breaks down at low confining stress. Using an established failure model, we show that while the majority of laboratory and terrestrial conditions lie in the linear regime, low-gravity planetary surfaces are situated in the nonlinear regime, where the bulk mechanical properties (apparent friction angle, apparent cohesion, and shear strength), become strongly stress dependent. We demonstrate that this nonlinearity governs the mechanical response of regolith in the limits of extremely low confining pressure found on low-gravity small-body surfaces, providing an explanation for the observations of very weak and uncohesive asteroid and cometary surfaces. Furthermore, we also show that mechanical properties of small-body regolith vary strongly with depth, with the apparent cohesion varying by orders of magnitude between the upper centimeters and depths of several meters. These results demonstrate that the widespread assumption of constant, stress-independent friction angle and bulk cohesion, inherent to linear strength models, fundamentally misrepresents regolith behaviour under low-gravity conditions, with important implications for small-body geomorphology, surface and rubble pile evolution, regolith simulants, and planetary exploration.
Related
- Experimental evidence for a physical alteration of fine regolith on near-Sun asteroids
- Insights into Lunar Regolith Maturity Differences and Shallow Regolith Evolution from Multisource Spectra
- Layering of lunar regolith at the Chandrayaan-3 landing site observed from the ChaSTE experiments from the lander
- Surface regolith model of near-Earth asteroid (3200) Phaethon
- Nickel isotopes in Apollo and Chang’e soils reveal widespread micrometeorite-driven processing of the lunar regolith
BibTeX
@article{murdoch2026rethinking,
title = {{Rethinking Regolith Strength: Why Nonlinearity Matters on Small Bodies}},
author = {Naomi Murdoch},
journal = {The Planetary Science Journal},
year = {2026},
month = oct,
doi = {10.3847/psj/aeaa37},
url = {https://iopscience.iop.org/article/10.3847/PSJ/aeaa37},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Rethinking Regolith Strength: Why Nonlinearity Matters on Small Bodies
AU - Naomi Murdoch
PY - 2026
DA - 2026/10/14
JO - The Planetary Science Journal
DO - 10.3847/psj/aeaa37
UR - https://iopscience.iop.org/article/10.3847/PSJ/aeaa37
AB - A widely used approach in planetary science to describe the strength and behavior of geological materials is the Mohr–Coulomb equation, yet it actually represents a linear approximation to a nonlinear failure envelope that breaks down at low confining stress. Using an established failure model, we show that while the majority of laboratory and terrestrial conditions lie in the linear regime, low-gravity planetary surfaces are situated in the nonlinear regime, where the bulk mechanical properties (apparent friction angle, apparent cohesion, and shear strength), become strongly stress dependent. We demonstrate that this nonlinearity governs the mechanical response of regolith in the limits of extremely low confining pressure found on low-gravity small-body surfaces, providing an explanation for the observations of very weak and uncohesive asteroid and cometary surfaces. Furthermore, we also show that mechanical properties of small-body regolith vary strongly with depth, with the apparent cohesion varying by orders of magnitude between the upper centimeters and depths of several meters. These results demonstrate that the widespread assumption of constant, stress-independent friction angle and bulk cohesion, inherent to linear strength models, fundamentally misrepresents regolith behaviour under low-gravity conditions, with important implications for small-body geomorphology, surface and rubble pile evolution, regolith simulants, and planetary exploration.
SN - 2632-3338
ER -