The Rock-Forming Minerals and Macroscale Mechanical Properties of Asteroid Rocks

Abstract

In the future, human activities in space, such as resource exploration and mining, will require the aid of geotechnical engineering. Rock samples obtained by sample-return missions via spacecraft and meteorites collected in the earth are usually rare, fragmented and arbitrarily shaped. These samples are difficult to be processed into coupon shapes required by traditionally macroscale rock mechanics testing methods (e.g., MTS tests), leading to the use of microscale rock mechanics experiments to derive the macroscale Young’s modulus of these samples. These microscale experiments have to then be upscaled to obtain macroscopic values. First, the performance of three upscaling methods are considered, two are based on effective medium theory and the third is the computational method of accurate grain-based modeling (AGBM). These methods are compared in the context of granitic samples, and the errors these three methodologies are quantified. The AGBM is found to be the most accurate, and is subsequently extended to measure the mechanical properties of unconventional rock samples, Hammadah al Hamra 346 (HaH 346) asteroid meteorites. Second, the microstructure, mineral composition and mechanical properties of rock-forming minerals in HaH 346 meteorites are measured using microscale rock mechanics experiment (micro-RME); these properties are used to generate accurate grain-based models. Last, the macroscale Young’s modulus of HaH 346 meteorites is upscaled and estimated using the validated AGBM method. The present methodology is a potential candidate for the characterization of the unconventional rock samples during asteroid mining.

Keywords: extraterrestrial rock mechanics, asteroid mining, macroscale Young's modulus, microscale rock mechanics experiment (micro-RME), accurate grain-based modeling (AGBM)