Probabilistic characterization of lunar lava tube collapses: Implications for reliability-based design, safety, and exploration

Abstract

• Stability of thousands of lava tube cross-sections were analyzed under lunar conditions. • Commonly used unimodal probability density functions can describe the gravity multipliers. • Collapse areas for layered roof follow bi-modal distributions rather than unimodal ones. • Linear increase in collapse area is observed for moderate roof thicknesses. • Significant differences in PDFs types are observed between homogeneous and layered cave roofs. • The impact of internal friction angle, autocorrelation function, and rock tensile strength was discussed. The study presents the results of over 30,000 numerical analyses on the stability of lava tubes under lunar conditions. The research considered random irregularities in cave geometry and their impact on stability, with a particular focus on the geometric characteristics of identified collapses. We propose a procedure for extracting the collapse areas and integrating it into the stability analysis results. The results were examined to assess the possibility of describing the geometry characteristics of collapses using commonly applied probability density distributions, such as normal or lognormal distribution. Our aim is to facilitate future risk assessment of lunar caves. Such an assessment will be essential prior to robotically exploring caves beneath the lunar surface and can be extended to be used for planetary caves beyond the Moon. Our findings indicate that several collapse characteristics can be represented by unimodal probability density distributions, which could significantly simplify the candidate selection process. Based on our results, we also highlight several key directions for future research and suggested implications related to their future exploration.