At the 50th Lunar and Planetary Science Conference earlier this month, a paper was presented describing a mission concept for a two-wheeled tethered robotic rover to explore lava tubes on the Moon. In addition to the scientific value of these windows into the lunar crust, lava tubes are ready-made natural structures that provide radiation protection, shielding from micrometeorites, and a shelter from the extreme temperature swings of the lunar surface. Perfect for lunar settlements!
https://www.hou.usra.edu/meetings/lpsc2019/pdf/1163.pdf