Lava tubes, even ones large enough to hold entire cities, could possibly exist on the Moon, according to new research.
The volcanic features are an important target for future human space exploration because they could provide shelter from cosmic radiation, meteorite impacts and temperature extremes.
Lava tubes are tunnels formed from the lava flow of volcanic eruptions. The edges of the lava cool as it flows to form a pipe-like crust around the flowing river of lava. When the eruption ends and the lava flow stops, the pipe drains leave behind a hollow tunnel, researchers explain.
"There has been some discussion of whether lava tubes might exist on the Moon," Jay Melosh from Purdue University, who was involved in the study, said in a statement. "Some evidence, like the sinuous rilles observed on the surface, suggest that if lunar lava tubes exist they might be really big."
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Sinuous rilles, which range in size up to 10 kilometers (6.2 miles) wide, are large channels visible on the lunar surface supposedly formed by lava flows.
Previous research has long suggested past volcanic activity on our Moon, ranging from the "man on the moon" being born from magma, to rock deposits supposedly from relatively recent volcanic activity that suggest the Moon was hot and unpredictable. So the existence of lava tubes on our close neighbor doesn't seem so far out of reach.
To determine whether such massive lava tubes could remain structurally stable on the Moon, researchers applied known information about lunar rock and the Moon's environment to civil engineering technology used to design tunnels on Earth.
"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," explained lead author 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."
Only one other study, published in 1969, has attempted to model lunar lava tubes. And now with this latest research, it seems future studies are needed to better understand our Moon's past, and whether it was really volcanically active and oozing with lava.
