Long-Term Environmental Influences on Lunar Regolith Simulant EAC-1

The Lunar Regolith Simulant EAC-1 [1] is manufactured to imitate with high fidelity the composition and granularity of the Moon's surface. It is designed to be used in large amounts of several cubic meters, and already is in some locations.

Influence of the environment on the regolith is still possible, such as temperature and humidity variations of the diurnal or annual cycles. These variations, and the potential accumulation of residual humidity, i.e., humidity that infiltrates but cannot ever be removed, will over time change the electromagnetic properties of the regolith simulant. In order to ensure reproducible radar propagation measurements in a testing environment filled with regolith simulant, it is very useful to track the variation of the changes of the electromagnetic properties, based on easier available measurements of temperature and humidity. Also, the change of material's electromagnetic properties when an ice fraction is added to the mixture, is currently an open question.

Preliminary lab measurements show a dependency of the material's electromagnetic properties with respect to an applied mechanical compressive force. This observation is in line with measurements presented by other groups [2].

We will present permittivity measurements with systematically varied volume fractions of relative humidity and material density, in order to try to extract a numerical model for the material's behavior.

 

[1] V. S. Engelschiøn, et al., “EAC-1A: A novel large-volume lunar regolith simulant,” Sci Rep, vol. 10, no. 1, Art. no. 1, Mar. 2020, doi: 10.1038/s41598-020-62312-4.

[2] D. Ramos Somolinos et al., “Electromagnetic Characterization of EAC-1A and JSC-2A Lunar Regolith Simulants,” Materials, vol. 17, no. 15, p. 3633, July 2024, doi: 10.3390/ma17153633.