The moon's first long-term inhabitants will require especially protective shelter. Cosmic radiation, extreme temperatures and the occasional meteorite impacts make the lunar surface a rather hostile place.

But the moon itself may provide the ideal solution -- massive underground lava tubes, big enough to house an entire city.

A new study by researchers at Purdue University suggests ancient lava eruptions may have left hollow pipe-like tunnels. Scientists have long considered the possibility that the moon boasts large lava tubes.

The lunar surface features large meandering river-like depressions called sinuous rilles. Some scientists have argued the channels are evidence of collapsed lava tubes or extinct lava flows. The new study by scientists at Purdue tested that suggestion, and found that it was possible for large lava tubes (sizes equal to the width of the moon's rilles) remain structurally sound.

"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," David Blair, a graduate student in Purdue's Department of Earth, Atmospheric and Planetary Sciences, explained in a press release.

"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," Blair added. "In theory, huge lava tubes -- big enough to easily house a city -- could be structurally sound on the moon."

The findings were presented last month at the Lunar and Planetary Science Conference, held in Texas.