Lava tubes are natural formations which follow volcanic activity. A stream of lava flows down an incline, the outside freezes while the interior continues flowing, until the interior is an empty tube. These tubes exist on Earth, and on the Moon and Mars.

On the Moon, these tubes are usually located near the boundaries of highland areas with Mares. Various popular articles have touted the possibility that future lunar settlements could house the habitats inside lava tubes. Tubes larger than 1000 feet in cross section may exist, buried under a hundred meters of hard rock. Continue reading Lava tubes on the Moon →