Apollo sample 70051 and high- and low-Ti lunar soil simulants MLS-1A and JSC-1A: Implications for future lunar exploration

Plans for establishment of a manned lunar base make it imperative that considerable research be performed on the use of lunar rocks and soil for in situ resource utilization (ISRU). Samples and simulants of lunar soil must be established for these studies. We present here the bulk and mineral chemistries of unusual Apollo 17 sample 70051, the <45-mu m fraction of 70051, and the bulk and mineral chemistries of lunar soil simulants MLS-1A, JSC-1A, and JSC-1Af. Comparison to lunar soils collected during the Apollo missions shows that 70051 has bulk chemistry similar to that of soils from the North Massif bounding the Valley of Taurus-Littrow. Particle-size distribution reveals 70051 to differ significantly from bona fide lunar soils. It is a coarse, immature sample with >80% of particles >50 mu m, and a constrained range of particle sizes (similar to 50% of particles are 50-100 mu m in size) when compared to typical Apollo 17 soils (e.g., 71501,1 has similar to 20% of particles in the 50-100 mu m range). Plagioclase, present in rock fragments and as mineral fragments (up to sizes similar to 1 mm), is the main phase present (50.5 vol%). Simulant JSC-1A has a chemistry that is atypical for most of the Moon and contains 49.3 vol% glass. Simulant MLS-1A resembles the FeO, TiO2 and Al2O3 contents of mare basalt soils. Both lunar soil simulants have specific properties for certain in situ resource utilization studies, however, neither fully matches both the physical and chemical characteristics of lunar soil. Sample 70051, as a 1.4-kg haphazard mixture of lunar soil particles, is probably the best of the Apollo "soil" samples to be allocated for various ISRU investigations, where the uniqueness of lunar soils is deemed a necessity for study.