The moon, as we know it, is largely dormant and inactive. Once upon a time though it was volcanically active. The empty tubes through which lave used to flow could provide a stable environment in which long term human settlements could be built according to a study presented at the Lunar and Planetary Science Conference on March 17.
According to Jay Melosh, a Purdue University distinguished professor of earth, atmospheric and planetary sciences, the tubes could provide shelter from the meteorite impacts, temperature extremes and cosmic radiation that would make the surface dangerous for a long-term human presence.
“There has been some discussion of whether lava tubes might exist on the moon. Some evidence, like the sinuous rilles observed on the surface, suggest that if lunar lava tubes exist they might be really big,” said Melosh in a statement.
“Sinuous rilles” are chillness visible on the lunar surface which are thought to have been formed by ancient lava flows. Some of these are up to 6 miles wide and the Purdue team believes that the underground tunnels could match those on the surface.
“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. 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,” said David Blair, a graduate student in Purdue’s Department of Earth, Atmospheric and Planetary Sciences.
The team, which encouraged further study of possible lunar caves, found that the potential stability of the tubes would depend on the “width, roof thickness and the stress state of the cooled lava.” A variety of possible cave structures were modelled using those variables and the researchers were encouraged by the results.
Only one previous study, in 1969, has been done on the possibility of deep lunar caves. However, in recent years the interest in permanent lunar settlements, research bases and mining operations has grown considerably.
As far back as 2006, NASA expressed interest in a permanent base that would have been completed by 2024. While that idea seems to have evaporated, it remains o possible future mission for the space agency. Then presidential candidate Newt Gingrich attempted to revive the plan in 2012.
In November of last year the European Space Agency unveiled plans for a lunar base, constructed largely by robots and 3D printing. Russia also announced plans for a permanent lunar settlement in May of last year.
China is the latest country to seriously discuss the possibility of mining the moon, but is certainly not the only country looking into the possibility.
If existing lunar caves and tunnels can provide structure as well as protection from radiation and temperature extremes on the moon it could considerably reduce the cost and potential time frame of these types of long term missions.
