Geologic and Thermophysical Characterization of Lunar Volcanic Pits

The LunarLeaper mission concept aims to explore subsurface lava tubes on the Moon. These are of interest for further robotic and human exploration, because such subsurface structures can provide shelter from the Moon’s hostile environment including radiation, large temperature fluctuations and micrometeorites. Satellite data has revealed that the lunar surface hosts hundreds of steep-walled pits. These pits have been hypothesized to represent collapsed ceilings of underground volcanic lava tubes, thus revealing unique insights into the subsurface and the geologic history of the Moon. Here, we characterize all currently known pit locations, as listed by Wagner and Robinson [2014], using globally available geologic, geomorphologic, and thermophysical information (from the Lunar Reconnaissance Orbiter LRO and the Selenological and Engineering Explorer SELENE). This enables us to map pit characteristics and relate them to the scientific, landing site, and operational requirements in the context of the LunarLeaper mission.

First, we study potential landing sites at each lunar pit considering that the rover will land in an area where the slope angle is smaller than 8° within a precision landing ellipse of 100 m. For each potential landing site, we quantify the visibility of the overall mission area, to determine if the robot would be able to establish line of sight with the lander antenna on the way to and once it reaches the volcanic pit. At the location with the best communication coverage, we evaluate the minimum distance to the pit, while considering slope and communication constraints. We also study the diurnal temperature variations which will set engineering requirements for the mission. Furthermore, we use the Unified Geological Map of the Moon, Fortezzo and Harrel [2020], to describe the geologic terrains hosting the pits. Finally, the characterization of all mapped lunar pits, allows us to perform an evaluation of landing sites most suited for LunarLeaper, while also providing constraints for any future missions targeting lunar pits.

 

References

Spudis P. D. Fortezzo, C.M. and S. L. Harrel. “Release of the digital Unified Global Geologic Map of the Moon at 1:5,000,000- scale.” In 51st Lunar and Planetary Science Conference, LPI Contribution, 2020. URL https://www.hou.usra.edu/meetings/lpsc2020/pdf/2760.pdf.

Robert V. Wagner and Mark S. Robinson. “Distribution, formation mechanisms, and significance of lunar pits.” Icarus, 237:52–60, 2014. ISSN 0019-1035. doi: https://doi.org/10.1016/j.icarus.2014.04.002. URL https://www.sciencedirect.com/science/article/pii/S0019103514001857.