Exploring Lunar Lava Tubes for Future Habitats
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Living on the moon presents formidable challenges due to its lack of atmosphere and magnetic protection. If humans are to establish a presence there, they must contend with meteoroids, solar radiation, and extreme temperature fluctuations.
One proposed solution is to inhabit subsurface caves or tunnels. Previously, evidence for such structures has come from over 200 intriguing vertical pits spotted on the lunar surface. Researchers suggest these pits might connect to extensive tunnel networks and massive underground chambers.
Recent studies have revealed that one of these pits, measuring about 328 feet (100 meters) deep and of similar width, connects to a lava tube that could extend for several miles. These lava tubes formed when the moon was geologically active, allowing molten lava to carve out long, hollow spaces beneath the surface.
"This is the first time we've directly shown that these caves exist," stated Lorenzo Bruzzone, a researcher from the University of Trento. "Our findings confirm the presence of a lava tube beneath the lunar surface."
The research team utilized radar data from NASA's Lunar Reconnaissance Orbiter (LRO) to support their findings, which were published in the journal Nature Astronomy. They developed a 3D model based on similar data from Earth’s underground caves.
"We believe we have modeled part of the conduit," said Leonardo Carrer, the study's lead author. "The best explanation for what we observed is an empty lava tube."
The Formation of Lunar Tunnels
NASA provides insight into how these lava tubes may have formed:
"Similar to those on Earth, lunar caves likely developed when molten lava flowed beneath a cooled lava field or when a solid crust formed over a river of lava, resulting in hollow tunnels. If the ceiling of such a tube collapses, it creates a pit or skylight that leads into the cave."
Experts speculate that several of the known vertical pits might be collapsed skylights leading to lava tubes. Previous data from NASA’s GRAIL mission hinted at several candidates for these structures, suggesting some could reach several kilometers in width and hundreds of meters in depth. The most recent candidate, reported in Icarus, appears connected to the Marius Hills vertical pit.
This presumed lava tube is estimated to be around 37 miles (60 km) long, 5.5 miles (9 km) wide, and as tall as a 16-story building.
Essential Protection for Future Colonists
While the contents of the Sea of Tranquility pit remain unclear, Robert Wagner, a planetary scientist at Arizona State University, noted that the analysis suggests a deeper passage than what visible imaging has shown.
If lava tubes exist, they would provide a stable thermal environment, avoiding the extreme temperature variations found on the surface, where daytime highs can reach 260 degrees Fahrenheit (127 C) and drop to minus 280 Fahrenheit (minus 173 C) at night. Temperatures in permanently shadowed areas of the Sea of Tranquility have been recorded at a consistent 63 degrees Fahrenheit (17 C).
These caves would also protect inhabitants and their equipment from harmful solar and cosmic radiation, as well as smaller meteoroids and larger asteroids. Unlike Earth, where small meteors mostly disintegrate in the atmosphere, the moon has no protective layer, allowing these objects to strike the surface without obstruction.
On Earth, a 10-pound meteoroid would create a spectacular fireball but would likely break apart due to atmospheric drag. In contrast, on the moon, it would retain its integrity until impact, potentially forming a crater 30 feet (9 meters) wide.
The Challenge of Living on the Moon
While lava tubes offer intriguing possibilities, they are not inherently habitable. Future lunar settlers would still require air, water, and food—resources that are scarce on the moon. While water and food might be transportable or potentially cultivable, breathable air would necessitate the construction of pressurized habitats.
NASA envisions establishing lunar housing by 2040, although this timeline may seem overly ambitious without substantial funding. The proposed solution involves 3D-printing homes using lunar concrete to reduce the costs associated with transporting materials from Earth, estimated to be around $1 million per kilogram.
Plans to return humans to the moon, known as Project Artemis, incorporate advanced technology and ambitious projections that leave many questioning the timeline for such aspirations. Before any structures can be erected, private enterprises collaborating with NASA must develop construction technologies suitable for the moon’s unique environment.
These technologies must function in:
- Low gravity and an oxygen-deficient atmosphere
- Extreme temperature conditions
- Fine, sharp lunar dust that is harmful to humans and equipment
- An environment vulnerable to solar storms that can disrupt operations even on Earth
Currently, the technology necessary to build habitats and infrastructure on the moon exists only in concept.
The resilience of a 3D-printed structure against impacts from high-velocity meteoroids and larger celestial objects remains uncertain, which may explain the growing interest in lava tubes among researchers.
Exploring the Possibility of Lunar Habitats
One concept proposed by advocates of lunar colonization is to pressurize these lava tubes. Engineers from Rutgers University and Blue Origin explored this idea, concluding that lunar lava tubes could serve as viable long-term habitats.
Their analysis, published in Acta Astronautica, confirmed the feasibility of pressurizing a small lava tube, potentially transforming it into a haven with breathable air.
However, little is known about the structural integrity of lunar lava tubes. Nevertheless, the prospect of establishing safe habitats in such tubes appears less daunting than constructing on the surface, especially as early settlers will need secure spaces while developing lunar infrastructure.
David Paige, a planetary scientist at UCLA, has studied the lunar pits identified by the LRO mission. He remarked, "Humans evolved living in caves, and we may return to that lifestyle on the moon."