We tend to think of future lunar colonies as being cramped futuristic domes or subsurface rabbit warrens, but what about underground caverns big enough to hang glide in? According to a study by a Purdue University team, that may not be so daft as it calculates that the Moon may contain lava tubes large enough to house entire cities.

The Moon may have a stark, silent majesty about it, but as a potential home it makes the Gobi desert look like paradise. Its atmosphere is only an academic argument away from being hard vacuum, it's surface is blasted by solar and cosmic radiation, its temperature during its month-long day ranges between far above boiling to deep below freezing, and it's constantly peppered with meteorites.

With that sort of environment, it's small wonder that scientists and engineers favor setting up shop underground rather than on the lunar surface. One option would be to excavate, and another might be to seek out pits on the Moon, but if you really want to build serious colonies, Purdue suggests lava tubes.

The latest Purdue study used current information about lunar rocks, geology, gravity, and environment and applied terrestrial principles of civil engineering. The researchers calculated that, given the potential width of the tubes, roof thickness, and the stress state of the cooled lava, the caverns could, barring major earthquake or meteorite impacts, be surprisingly large.

"We found that if lunar lava tubes existed with a strong arched shape like those on Earth, they would be stable at sizes up to 5,000 meters, or several miles wide, on the Moon," says Purdue graduate student David Blair. "This wouldn't be possible on Earth, but gravity is much lower on the Moon and lunar rock doesn't have to withstand the same weathering and erosion. In theory, huge lava tubes – big enough to easily house a city – could be structurally sound on the Moon."