Exploration of Vertical Holes Near the Lunar Polar Regions to Confirm the Presence of Water in Underground Caves and Their Utilization

Japan has identified underground caves on the Moon near the lunar equator, likely associated with large vertical holes caused by past volcanic activity. Additionally, lava tubes formed by meteorite impacts have also been observed near the polar regions. The confirmation of water stored as ice is considered a primary motivation for exploration, particularly near the Moon’s south pole. Potential sources of this water include asteroid impacts and the solar wind. While significant quantities of water have yet to be detected on the lunar surface, these underground caves, shielded by substantial overhangs and in permanent darkness, are considered locations where water stored as ice is expected to accumulate due to its difficulty in escaping. This paper outlines a proposed mission to investigate areas near these polar holes throughout the lunar day, finding a traversable route by land from a prospective landing site to these polar vertical holes and considers methods of investigating the interior of shallow vertical holes. Furthermore, this paper examines possible missions within the lunar landing plan currently being developed for the NASA-led Artemis program. Based on information about the program, we consider the feasibility of Japan independently exploring and utilizing the Moon. Artemis III, which plans to have nine landing sites near the south pole and is expected to use Starship for landing, and JAXA’s ongoing development of a pressurized manned rover, will significantly facilitate valuable lunar exploration.