Micromechanical testing and property upscaling of planetary rocks: A critical review

Knowledge of the mechanical behavior of planetary rocks is indispensable for space explorations. The scarcity of pristine samples and the irregular shapes of planetary meteorites make it difficult to obtain representative samples for conventional macroscale rock mechanics experiments (macro-RMEs). This critical review discusses recent advances in microscale RMEs (micro-RMEs) techniques and the upscaling methods for extracting mechanical parameters. Methods of mineralogical and microstructural analyses, along with non-destructive mechanical techniques, have provided new opportunities for studying planetary rocks with unprecedented precision and capabilities. First, we summarize several mainstream methods for obtaining the mineralogy and microstructure of planetary rocks. Then, nondestructive micromechanical testing methods, nanoindentation and atomic force microscopy (AFM), are detailed reviewed, illustrating the principles, advantages, influencing factors, and available testing results from literature. Subsequently, several feasible upscaling methods that bridge the micro-measurements of meteorite pieces to the strength of the intact body are introduced. Finally, the potential applications of planetary rock mechanics research to guiding the design and execution of space missions are environed, ranging from sample return missions and planetary defense to extraterrestrial construction. These discussions are expected to broaden the understanding of the microscale mechanical properties of planetary rocks and their significant role in deep space exploration.