Research on the Mechanical Properties of Mojave Mars Simulant-1 (MMS-1) Soil

Abstract

According to the mission scenario of the International Space Exploration Collaboration Group (ISECG), a "Mars sample return plan" is underway to bring the soil of Mars back to Earth by 2030. In the near future, in order to efficiently perform various operations on Mars (filling, excavation, sampling, ground improvement, etc.), presimulation on Earth will be important. Therefore, there is an urgent need to develop an appropriate simulated soil and to understand its material and mechanical properties. Based on this background, the authors are investigating the physical and basic mechanical properties of Mojave Mars Simulant soil (MMS-1), which has been reported as a simulated soil for Mars. This study focused on the particle shape of MMS-1 and was conducted to investigate the effect of particle shape on shear strength and volume change. As a result, it was revealed that MMS-1 has a higher shear strength than Toyoura sand and has a clear peak as the relative density increases. Moreover, MMS-1 is a material that causes volume expansion during shearing even for low stress and density states compared with artificial soil, and it was revealed that this is due to the angularity of the MMS-1 particles.

Interface Direct Shear Tests on JEZ-1 Mars Regolith Simulant

“…All the interface c cv values are lower than the cohesion of JEZ-1 (3.2 kPa). The cohesion and adhesion of JEZ-1 in this paper are lower than 5 kPa, in accordance with the in-situ data from wheel trenches or wheel scuffs [8,9]. cpeak values of the smooth and rough interface are 1.5 kPa and 4.3 kPa, and the ccv values are 1.5 kPa and 2.8 kPa, respectively.…”

“…All the interface ccv values are lower than the cohesion of JEZ-1 (3.2 kPa). The cohesion and adhesion of JEZ-1 in this paper are lower than 5 kPa, in accordance with the in-situ data from wheel trenches or wheel scuffs [8,9]. All the tests on JEZ-1 simulant-steel interface for the two considered roughness are summarized in the Mohr plane in Figure 10 and compared with the results of soil-soil.…”

“…From the grain size distribution test, the effective grain size (d 10 ) of JEZ-1 is 4.9 µm and the coefficient of uniformity (C u ) is equal to 14.3, indicating that JEZ-1 is a well-graded Martian simulant. The mean grain size (d 50 ) of JEZ-1 is 57.2 µm, lower than the d 50 values of JSC Mars-1 (200 µm) and MMS-1 (120 µm), according to the data from [7,8]. This highlights that JEZ-1 has finer grains than the other two simulants (i.e., JSC Mars-1 and MMS-1), in agreement with the fact that the Jezero Crater Delta contains clays, as revealed by the Mars Reconnaissance Orbiter's CRISM instrument.…”

“…The average initial sample height for direct shear and interface direct tests are 31.59 mm and 27.58 mm, respectively. Since very loose or very dense Martian regolith is not likely to encounter in the in-situ conditions, the average values of density (ρ a ) and relative density (D r ) are 1.84 g/cm 3 and 86.28%, therefore all the samples for the two kinds of shear tests are dense [6,8,29].…”

“…JEZ-1 is specifically designed for the scientists and engineers looking to learn more about the landing site (Jezero Crater) of the Perseverance Rover and the scientific research that can be done there. The direct shear test is applicable to understand the mechanical behavior of Martian regolith, especially under different stress or strain conditions (e.g., large strains or critical state), according to [5][6][7][8]. The parameters of cohesion/adhesion and (interface) friction angle obtained from the direct shear test are fundamental information for the design of rover (e.g., landing systems and wheels) that is in contact with the Martian soil [7,9].…”