Could microbes survive in the permanently shadowed regions (PSRs) of the Moon?
This is what a recent study presented at the 56th Lunar and Planetary Science Conference hopes to address as a team of researchers from the United States and Canada investigated the likelihood of long-term survival for microbes in the PSR areas of the Moon, which are craters located at the poles that don’t see sunlight due to the Moon’s small axial tilt.
This study has the potential to help researchers better understand unlikely locations where they could find life as we know it throughout the solar system.
Here, Universe Today discusses this incredible research with Dr. John Moores, who is an associate professor in the Centre for Research in Earth and Space Science at York University and lead author of the study, regarding the motivation behind the study, significant results, how these findings could influence human exploration to the PSRs, possible contamination from human exploration, and how any microbes could have arrived at the PSRs.
Therefore, what was the motivation behind the study?
“A few years ago in 2019, I participated in a study looking at the potential for the Moon to preserve microbial contamination on spacecraft, led by University of Florida researcher Dr. Andrew Schuerger,” Dr. Moores tells Universe Today.
“At the time, we did not consider the PSRs because of the complexity of modelling the ultraviolet radiation environment here. However, in the years since, a former student of mine, Dr. Jacob Kloos at the University of Maryland, had developed a sophisticated illumination model.
Furthermore, with the renewed interest in PSR exploration, we decided to take another look at these regions and realized we had all the pieces of the puzzle we needed to understand their ability to preserve terrestrial microbial contamination.”
For the study, the researchers conducted a series of models to ascertain if the reduced amount of ultraviolet (UV) radiation and increased temperatures within the PSRs could enable the possible survival of microorganisms within two PSR craters, Shackleton and Faustini.
The researchers chose these two craters based on previous studies involving the modeling of light entering the craters and both craters are also current landing site targets for the upcoming Artemis missions.
As noted, the lunar PSRs are devoid of sunlight due to the Moon’s axial tilt, which is approximately 1.5 degrees with respect to Sun.
For context, the Earth’s axial tilt is approximately 23.5 degrees with respect to the Sun, resulting in the seasons we experience as Earth orbits the Sun. As a result from this small axial tilt, certain lunar PSRs crater like Shackleton and Faustini have not received sunlight in potentially billions of years.
While the Moon lacks an atmosphere and is exposed to the vacuum of space, this creates very cold pockets that the researchers propose could preserve microbes for long periods of time. Therefore, what are the most significant results from this study?
“In space, microbes are typically killed by high heat and ultraviolet radiation,” Dr. Moores tells Universe Today.
“However, the PSRs are very cold and very dark and, as a result, they are one of the most protective environments in the solar system for the kinds of microbes that are typically present on spacecraft.
To be clear, those microbes cannot metabolize, replicate or grow here, but they likely remain viable for decades until their spores are killed by the effects of vacuum. The organic molecules that make up their cells likely would persist far longer.”
As noted, the lunar PSRs are currently targeted landing sites for the upcoming NASA Artemis program, most notably Shackleton, due to the potential pockets of water ice that are trapped within the PSR craters that future astronauts could use for water, fuel, and oxygen. However, all space missions run the risk of bringing unwanted microbes to the target location, thus potentially and unnecessarily contaminating an otherwise pristine location devoid of microbes. This could result in faulty data being collected and inaccurate results after analyzing the data, potentially leading to inaccurate findings regarding finding life beyond Earth.
This is especially true for human missions to the Moon, as humans are naturally dirty creatures that carry a myriad of microbes that could travel with them to the Moon. Thus, whatever microbes that could exist within the PSRs could become influenced by human microbes, possibly killing them off.
To combat this, the NASA Planetary Protection office is tasked with overseeing that outgoing spacecraft are sterilized and clean of microbes prior to launch but also tasked with ensuring returned spacecraft did not carry unwanted microbes from outside the Earth. Therefore, how can the findings from this study influence human exploration in lunar PSRs?
Dr. Moores tells Universe Today, “While we can clean robotic spacecraft fairly well, it is more difficult to decontaminate equipment and spacesuits used in human exploration. As a result, humans walking into the PSRs will likely carry considerably more contamination with them, some of which will be left behind and be preserved far longer than anywhere else on the moon.”
Additionally, the study notes that “care should be taken in their exploration” regarding the PSRs, but is this referring to planetary protection?
Dr. Moores tells Universe Today, “It is less a question of planetary protection than of preserving the PSRs in as close to a pristine state as possible for future scientific analyses. The question then is to what extent does this contamination matter? This will depend on the scientific work being done within the PSRs. One possible goal is to retrieve samples of water ice from within the PSRs to better understand their origins and how they came to be found here. Part of that analysis could include looking at organic molecules present in the ice that are known to occur in other places, for instance within comets. That analysis will be easier if contamination from terrestrial sources is minimized.”
If there are microbes at the lunar PSRs, the question then becomes how they arrived there. Given the heavily-craters surface of the Moon, they could have arrived from an impacting body from elsewhere in the solar system, or beyond. However, humans have also sent a number of spacecraft that have impacted the lunar surface, including the Ranger spacecraft that occurred leading up to the Apollo missions, but these spacecraft crashed near the Moon’s equator and far from the poles.
In 2009, NASA’s Lunar Crater Observation and Sensing Satellite (LCROSS) mission to the Moon intentionally crashed its Centaur upper stage into Cabeus crater, which is a PSR crater located approximately 100 kilometers (62 miles) from the lunar south pole, with the goal of measuring the amount of water produced from the ejecta plume. But, how could microbes have arrived in lunar PSRs and what can this teach us about the Moon’s formation and evolution?
“The chance that there is already terrestrial microbial contamination in the PSRs is low but not zero,” Dr. Moores tells Universe Today. “Several spacecraft have impacted within or near the PSRs. Though they all did so at high speed, past research by others has suggested that small numbers of spores can survive simulated impacts into regolith-like materials. If any microbes survived those impacts, they would have been widely dispersed.”
What new discoveries about potential microbes living on the Moon will researchers make in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!
Written by Laurence Tognetti, Universe Today.
