Moon Caves With Stable Spring-Like Temperatures Discovered, Ideal Place for a Moon Base

"Humans grew up in caves, and if we ever live on the moon, we might go back to caves," said Paige, who is in charge of the Diviner Lunar Radiometer Experiment analyzing Moon caves.
moon caves

As companies race to build the rockets and spacecraft to get the Moon’s resources, has much thought been given to the best place to establish a Moon base where people can live? One team of UCLA (University of California, Los Angeles) scientists led by Tyler Horvath has given it much thought. Tyler Horvath is a UCLA doctoral student in planetary science who took a particular interest in the Moon caves.

Apart from the lack of oxygen up there, the Moon can be inhospitable for other reasons. The Moon’s surface has temperatures all over the place, from boiling hot to freezing cold, and the only place you can hide from the harsh space environment are the Moon caves.

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The Moon’s surface gets as hot as 260°F (127°C) during the day and as cold as 280°F (138°C) below zero at night.

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Holly Ober writing for newsroom.ucla.edu describes a day on the Moon and the challenges of staying there. A day on the Moon is about 15 Earth days long. During that time, the Moon’s surface is constantly hit by sunlight and is often hot enough to boil water. The nights equivalent to 15 Earth days long are so cold that they are hard to imagine. Making heating and cooling systems that can work in these conditions and making enough energy to run them all the time could be an impassable barrier to exploring or living on the Moon. Even though solar power is NASA’s primary power source, it doesn’t work at night. 

What are the best places on the Moon to live? 

Using temperature data gathered from the Diviner Lunar Radiometer Experiment, researchers at UCLA seem to think anyone who plans to live on the Moon should consider living underground. The researchers have found shady places in pits and caves that they might lead to on the Moon, where the temperature is always around 63 degrees Fahrenheit (17 Celsius). 

Mare Ingenii presumed lava tube skylight
Moon cave by NASA/LROC/ASU

These would be the best places for people to create Moon bases where they and their equipment will be safe from the heat and cold.

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Moon caves are 5 to 9 degrees cooler than room temperature

63 degrees Fahrenheit is cooler than room temperature. Room temperature is between 68 and 72 degrees Fahrenheit, depending on the source. At 63 degrees Fahrenheit, some of us may feel a little bit of a chill, but it is better than boiling or freezing to death on some parts of the Moon’s surface.

A study of over 200 pits on the Moon

Since 2009, when scientists first found holes on the Moon, they have wondered if they led to Moon caves. Horvath said that about 16 of the more than 200 pits are likely collapsed lava tubes. 

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Moon cave/crater by NASA

Moon pits likely have lava-formed tubes leading to Moon caves

Two noticeable pits have overhangs that clearly lead to some cave or void. This study shows that a pits overhang may also lead to a large cave.

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On Earth, lava tubes form when molten lava flows under a field of hardened lava or when a crust forms on top of a river of lava, leaving a long, hollow tunnel. If the ceiling of a hardened lava tube falls in, it makes a hole that can be used to get into the rest of the cave-like tube.

A good spot to set up a Moon base?

Not every Moon cave is suitable for a Moon base. When researchers analyzed the ‘Tranquillitatis pit,’ a pit closest to the Moon’s equator, where it gets the most sun, the pit floor could get close to 300 degrees during the day, possibly 40 degrees hotter than the rest of the Moon’s surface.

Improving early temperature maps of the Moon

Since 2009, Diviner has been continuously mapping the Moon. It is now NASA’s second largest planetary dataset, and its thermal measurements are the most detailed and complete of any object in our solar system, including Earth. The Diviner experiment’s data have been improved by the team’s current work on lunar pits.

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Horvath leading the research, said, “Since Diviner had never been used to look at things this small before, we found that it had a bit of double vision, which made all of our maps a bit fuzzy.” The team has lined up as many images taken by the instrument until they could get an accurate thermal reading down to the level of a single pixel. This method led to maps of the Moon’s surface with much better detail.

Searching for suitable Moon caves using modeled data

Early data from this thermal modeling project for the lunar pit were used to help design the rover’s thermal management system for NASA’s proposed Moon Diver mission. Horvath and Hayne were on the science team for this mission. The goal is to have the rover rappel into the Tranquillitatis pit to study the layers of lava flows in its walls and to look for any caves that might be there.

Thermal camera used to survey the Moon for hospitable temperatures

Horvath and Paige, members of the science team for L-CIRiS (Lunar Compact Infrared Imaging System), say that a new thermal camera will be sent to the Moon’s south pole in late 2023. L-CIRiS is led by Paul Hayne and will be the first thermal camera used on the ground.

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What next?

NASA has no plans to set up an exploration base camp or live on the Moon right now, let alone establish a base in one of the deep Moon caves. This research may help future scientists determine the best spot for a moon base. Russia and China are already planning to set up a moonbase together.

Building bases in the shaded parts of these pits would protect astronauts from cosmic rays, solar radiation, and small meteorites. Astronauts will be able to focus next on growing food, gathering materials for experiments, and making the base bigger. 

Given that the cheap seats for a brief trip to the edge of space on a Virgin Galactic flight are $450,000, most of us can barely afford to touch space, let alone consider whether it will be warm or cold on a Moon base. 

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For now, most people will make do with keeping their sweaters for the chill on Earth and maybe pack them up for their grandchildren, who might one day colonize Mars.


Featured image credit: Moon cave by John Lowery/NASA