The dream of building a permanent colony on the Moon: a place where humans from all walks of life can come together and give birth to a new culture and identity. A place where vital scientific research and experiments can be conducted, lunar industries created, and people can do a little ‘adventure tourism’. It has been the subject of science fiction and speculative literature for over a century. But in the years to come, it could very well become a reality.
This presents many challenges but also opportunities for creative solutions. For years, astronomers have speculated that the perfect location to create a lunar colony was underground, especially in pits, caves, and stable lava tubes visible and accessible from the lunar surface. According to new research from CU Boulder, preliminary results show that these pits are remarkably stable relative to surface conditions.
The research was led by graduate student Andrew Wilcoski of the Department of Astrophysical and Planetary Sciences at UC Boulder, who presented the group’s initial findings at the fall 2021 meeting of the American Geophysical Union (AGU) in New Orleans. This presentation, titled “Thermal Environments and the Volatile Trapping Potential of Lunar Pits and Caves”, proposes new 3D thermal models to characterize temperature environments in lunar pits and caves, with the ultimate goal of assessing the stability of the moon. a range of volatile species in these pits.
Thanks to missions such as NASA’s Lunar Reconnaissance Orbiter (LRO), twin satellites Gravity Recovery and Interior Laboratory (GRAIL) and JAXA’s SELenological and Engineering Explorer (SELENE) – aka. Orbiter “Kaguya” – scientists understand that the Moon has many pits and caves located on its surface. In many cases, these are stable lava tubes that formed when the Moon was still volcanically active billions of years ago.
In many cases, these tubes have collapsed into one or more sections (mainly due to impacts), creating holes from the surface inward (aka âskylightsâ). These sites are considered to have great potential for future research missions, as they would provide insight into volcanic history and the impact of the Moon. Mission planners from NASA, ESA, Roscosmos and the Chinese National Space Agency (CNSA) are also studying them as possible sites for future human exploration.
These pits and caves could provide resources for future human exploration, not least of which are volatile elements (like water ice). In the right abundance, this ice could be harvested and used to provide astronauts with clean water, showers, and even rocket fuel. Additionally, these pits could be ideal for providing shelter that would protect astronauts (and perhaps even settlers) from hostile surface conditions – i.e. extreme temperatures, micrometeorite bombardment, and radiation on the lunar surface.
âIf we are hoping to send people to these caves in the decades to come, we want to know what to expect there,â Wilcoski said in a recent CU Boulder Today press release. To learn more about their suitability, Wilcoski and planetologist Paul Hayne – assistant professor in the Atmospheric and Space Physics Laboratory at CU Boulder and co-author of the research – conducted a series of computer simulations to recreate the conditions below. the surface of the Moon.
Their early findings indicate that lunar pits and caves provide stable temperature conditions that would help astronauts overcome some of the Moon’s most extreme phenomena. However, these same conditions would make them less than ideal for finding abundant supplies of water ice. In fact, most of the team’s simulated caves hosted temperatures of around -120 to 70 Â° C (-184 to 94 Â° F) throughout a lunar day.
Previous research by Hayne and other scientists has shown that hidden treasures of water ice may have accumulated in certain lunar “cold traps” for billions of years. But, based on these new simulations, many lunar pits and caves are probably too hot to house similar treasures. Ironically, this problem is similar to the situation on the lunar surface, where water ice cannot exist for long due to extreme temperature variations.
âAs you approach the equator, temperatures can reach over 100 degrees Celsius during the day on the surface, and they will drop to 170 degrees Celsius below zero at night,â Wilcoski said.
Therefore, most mission planners are currently searching cratered polar regions for potential sites to build habitats. The crater floors in these permanently shaded areas act as “cold sinks” that maintain constant freezing temperatures – hence the reason why abundant water ice reserves have been observed there. Similarly, the key to finding pits and caves that may contain ice depends on geographic location and orientation.
While pits at low to mid latitudes are too hot to trap volatiles, pits at higher latitudes may have the right geometry and temperatures to keep water ice stable over time. In addition, the simulations showed that orientation also plays an important role. For example, if the mouth of a cave pointed directly at the rising sun, it would experience scorching temperatures throughout the day, then plunge into freezing depressions at night (compared to others that remained freezing).
Another plus point to all of this, according to Hayne, is that no one knows how many pits and caves could be on the lunar surface. According to research based on LRO data (Wagner and Robinson, 2014), there could be more than 200 ranging from 5 meters (~ 5 yards) to 900 meters (~ 984 yards) in diameter. Ultimately, this latest research highlights the need to know the thermal environments in lunar pits and presents exciting possibilities for possible lunar habitats.
âThese are great options for establishing a long-term human presence on the moon. One interesting possibility would be to establish a protected base station inside a pit or moon cave near one of the polar craters containing water ice. Astronauts could then venture out when the conditions were right to collect ice-rich soil. “
As they indicated in their presentation, the next iteration of their thermal simulations will include a âcoupled Monte Carlo ballistic jumpâ statistical model that will assess the vapor pressure for how long water can stay in these pits. The ballistic model will allow scientists to measure the role that pit geometry and latitude play in trapping different types of volatile elements and predict the concentrated volatile compositions that may exist in lunar pits.
In the coming years, several space agencies plan to build moon bases in the South Pole-Aitken basin, with possible base sites including Shackleton and Shoemaker craters. These bases would be able to harvest ice from the bottom of the crater to meet their water needs and ensure their power supply by positioning solar panels around the edge of the crater (with the option for nuclear reactors and fuel cells as well) . But who said that all the bases will be established in these environments?
Others may still reside in the polar regions but be located underground in stable lava tubes with large caches of water ice. Who knows? If and when real estate becomes more in demand, settlers and commercial interests may find that there is little room left for surface habitats, and they will have to build habitats in pits and caves around the poles. There is even the possibility of establishing settlements in lava tubes large enough to house entire cities.
We’re going back to the moon, okay. But this time, we plan to stay – possibly indefinitely!
Further reading: CU Rock, AGU