Scientists have talked about the possible existence of lava tubes on the moon. The tubes are believed to have enough capacity to hold entire cities. As per the researchers, the volcanic features are an essential target for future human space exploration because there is a possibility that they might give shelter from cosmic radiation, meteorite impacts and temperature extremes.

Lava tubes are tunnels formed by flowing lava of volcanic eruptions. The edges of the lava cool when it flows to form a pipe-like crust around the flowing river of lava. The researchers said when the eruption and the lava flow stops, a hollow tunnel has been left behind by the pipe drains.

Jay Melosh from Purdue University, who was involved in the study, said that some talks have been there whether lava tubes could exist on the Moon. Adding to it, Melosh also said that some evidence, like the sinuous rilles noticed on the surface, hints if lunar lava tubes exist they could be really big.

According to researchers, Sinuous rilles are large channels noticeable on the lunar surface allegedly formed by lava flows. Sinuous rilles range in size up to 10 kilometers (6.2 miles) wide. The researchers want to know whether such huge lava tubes might remain structurally stable on the Moon. So, to know this, they applied information regarding lunar rock and the Moon's environment to civil engineering technology that utilized to design tunnels on Earth.

Lead author David Blair said they found if lunar lava tubes existed with a strong arched shape similar to those on Earth, they might be stable at sizes up to 5,000 meters, or numerous miles wide, on the Moon.

"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", Blair added.