Earthly microbes carried unintentionally by human missions may be able to survive in parts of the Moon’s south pole, according to a new study that points to previously overlooked conditions that could protect microorganisms from the lunar environment.
The researchers found that some microbes could remain alive in a suspended state, known as cryptobiosis, in areas with low temperatures and limited ultraviolet radiation. The findings suggest lunar polar regions may be less hostile to microbial survival than previously thought.
“Some of Earth’s microbes likely to hitch a ride to space with human explorers could survive in the shaded nooks and crannies of the Moon’s South Pole region,” NASA scientists said.
Why the lunar south pole matters
The Moon's south pole has conditions that differ from much of its surface. Because of the low angle at which sunlight reaches the region and its varied terrain, some areas receive far less solar radiation.
These conditions create permanently shadowed regions where water ice can remain stable. They can also result in lower temperatures, reduced ultraviolet exposure and lower energetic particle flux.
Earlier research had suggested that the lunar surface was largely too harsh for microbial survival. A 2019 study identified ultraviolet radiation, extreme temperatures and energetic particle radiation as major obstacles.
The newer research examined how hills, valleys and other topographical features could create pockets with more favourable conditions.
Five types of microbes could survive
Researchers compared lunar surface maps with existing survivability data for three types of bacteria and two types of fungi commonly associated with crewed space missions, reported Mint.
The analysis found areas around the lunar poles where conditions could allow these microorganisms to survive, although not grow or reproduce.
The study said survival would be possible in a “cryptobiotic state”, meaning the microbes could remain alive until more favourable conditions emerged.
Study co-author Prabal Saxena told Space.com that even small features could offer protection. “Even a bootprint or a rover's tread may create a habitable area,” he told Mint.
Chandrayaan-1 data helped assess radiation
Data from India's Chandrayaan-1 mission also contributed to the assessment of the lunar radiation environment.
Per Mint report, researchers used results from the mission's Radiation Dose Monitor (RADOM), along with data from the Lunar Reconnaissance Orbiter's CRaTER instrument, to examine galactic cosmic ray exposure around the Moon.
The study noted that radiation measurements from LRO CRaTER and Chandrayaan-1's RADOM indicated destruction timescales of more than 1 million years when particle fluxes and cross sections were considered.
RADOM, a miniature dosimeter-spectrometer, measured absorbed radiation doses and energy deposited by high-energy particles during Chandrayaan-1's journey and lunar orbit.
Could human missions contaminate the Moon?
The findings raise concerns about biological contamination as more human missions target the lunar surface.
NASA notes that carrying microbes during human spaceflight is difficult to avoid: “Humans have, on average, 1 million bacteria living on each patch of skin the size of a pencil eraser, for example. These bacteria vent from spacesuits and habitats.”
Study co-author Heather Graham told Mint, “Our findings show that we need to be even more thoughtful about the materials that we might unintentionally take with us when we are exploring space, and the impacts that we might have.”
Researchers also said understanding contamination will be important for future searches for life on Mars.
“We need to understand what was there before us, because when we go to Mars to search for signs of life beyond our planet, we will want to make sure it’s not stuff we brought,” said Andrew Needham, a NASA Goddard-based paper co-author.
The researchers also suggested that the Moon could preserve traces of ancient material from Earth, with Saxena saying, "The moon might be like Earth's freezer, preserving really interesting bits of evidence of Earth's past if they landed at the moon's poles."