The regolith properties of the Chang'e-5 landing region and the ground drilling experiments using lunar regolith simulants
The Chang'e-5 (CE-5) mission is China's first lunar sample return mission. The Rümker region in northern Oceanus Procellarum was selected as the landing area. CE-5 will automatically sample ~ 2 kg of lunar samples from the surface and subsurface. Previous studies focused more on the geological background of the landing region. However, the lunar regolith properties also have a significant influence on the mission, especially drilling, and thus should be studied and constrained. In this research, we analyzed the lunar regolith properties of the CE-5 landing region first using remote sensing measurements. The western maria and eastern maria in the landing region are both covered by very low-Ti to low-Ti basaltic regolith. The western mare regolith, with longer exposure to space weathering, is more mature, finer, and thicker than the eastern mare regolith. CUG-series lunar regolith simulants were then produced based on our analysis (physically and chemically) of the regolith properties of CE-5 landing region and compared to Apollo soils. Finally, the lunar simulants were used to perform ground drilling experiments to support the drilling of the CE-5 mission. In a fixed rotation speed (120 rpm), feed speed (120 mm/min), and total drilling depth (~1 m), 274, 291, and 346 g of lunar simulants were cored on simulants Mixture-1, Mixture-2, and Mixture-3, respectively. Our experiments suggest that it is easier to drill and core finer and looser lunar regolith. In this case, the western mare regolith is easier for drilling than the eastern mare regolith. However, samples from the eastern young maria (Em3, Em4) are scientifically more meaningful. We propose that landing on, and drilling in, a smooth and mature area in unit Em4 should be the highest priority for the CE-5 mission; this can be accomplished by careful landing site selection, precise landing and optimized drilling control.