Weight Loss and Gain of Lunar Regolith Simulants, with Notes on Sample Variation

Lunar regolith simulants characteristically have H2O molecules on the surface of the particles. These molecules are not found on in situ lunar particles. As the H2O is on the surface of the particles, it can disproportionately enter into processes, potential distorting results from the desired lunar behavior. The H2O molecules under consideration are not present as water, their molecule to molecule relationship is different, making drying at 110 °C ineffective. Drying the simulant at 200 °C removes most of the problematic molecules. Such baking is part of the NASA standard issued by the NASA Chief Engineer. This paper assembles what is currently known about such drying, including the weight lost in the drying, and the effect of simulant bed depth. This paper also assembles what is known about how rapidly a dried simulant regains H2O from the atmosphere. Recommendations are given on how to do the drying and how to store a dried simulant.