By Will Dunham
WASHINGTON, Aug 21 (Reuters) - The moon is, to put it mildly, an inhospitable place for people and other living organisms from Earth, with its lack of breathable air, extreme temperatures and exposure to relentless space radiation and energetic particles. That is why astronauts wear spacesuits and spacecraft are built with shielding.
But how about the microbes that inevitably will hitchhike with astronauts during space exploration?
New research led by NASA scientists looking at five forms
of fungi and bacteria indicates that some of them indeed could survive for a time under certain conditions on the lunar surface — a finding that raises concerns about unintended life transfer to the moon.
These microbes were tested in modeling simulations of three regions near the lunar South Pole — Nobile Rim, Connecting Ridge and de Gerlache Rim — using environmental conditions based on observations by NASA's Lunar Reconnaissance Orbiter and data on radiation exposure.
The simulations indicated that some of the microbes could survive for periods of weeks to months in certain areas — such as inside craters that remain permanently shadowed — and during particular seasons — autumn and winter, according to planetary scientist Prabal Saxena of NASA's Goddard Space Flight Center in Maryland.
The two fungi studied proved to be hardier than the three bacteria species. Aspergillus niger, a common fungal species prevalent in warmer climates and sometimes called "black mold," was the most resilient.
Aspergillus flourishes in warm and damp places like bathrooms and heating, ventilation and air conditioning systems. Astronauts have found it inside the International Space Station. Experiments have shown it can even survive outside the station while in orbit.
The researchers also studied several species of Fusarium, a common soil-borne fungus.
"Aspergillus was the most well-suited to survive in regions of the lunar poles. Fusarium was similarly resilient, though not to the extent of Aspergillus," said Saxena, lead author of the study published this week in the journal Science Advances.
THREE BACTERIA SPECIES
Three bacteria species were studied: Deinococcus radiodurans, a soil-borne microbe known for withstanding cold and radiation; Staphylococcus aureus, often found on the skin and inside nasal passages; and Bacillus subtilis, found in soil, vegetation and the human gastrointestinal tract.
"The bacteria we examined were less resilient to ultraviolet radiation and consequently had less survival, with Deinococcus leading the way and Staphylococcus and Bacillus bringing up the rear," Saxena said.
UV radiation and heat — lunar daytime temperatures can reach roughly 260 degrees Fahrenheit (127 degrees Celsius) — were the biggest threats, along with energetic particle radiation and the natural vacuum effects on the moon's surface.
The models revealed maps of "survivable niches" as large as crater floors miles wide. Aspergillus in the models could survive even in areas with some sunlight — hence UV radiation — exposure.
"Our study focused only on the survival of these cells, not their growth or reproduction," said Goddard Space Flight Center organic geochemist and study co-author Heather Graham.
"But there are scenarios where cells can get buried, which would keep them warm and protected from radiation. There may also be scenarios where pockets of liquid water could form, which would potentially help the organisms grow," Graham said.
These microbes could affect resources such as water — present as ice in some places on the moon — that are potentially useful for astronauts, the researchers said.
The study did not look at whether lunar conditions could cause mutations making the microbes more dangerous as pathogens.
"The study merely looked at cellular persistence and not mutation so we can't extend these results to include any details of future pathogenicity," Graham said.
FUTURE MISSIONS
The United States and China are pursuing plans to return astronauts to the lunar surface for the first time since 1972 and establish longer-term moon bases. NASA's Artemis program aims to land astronauts around the South Pole region.
There is concern that contamination by Earth microbes might skew scientific understanding of the moon.
"We found that the lunar South Pole and North Pole possess significant regions that may allow common human-associated microbes to survive long enough to impact scientific operations and exploration," Saxena said.
Bringing microbes along on space journeys may be unavoidable, with human bodies naturally rife with them.
"When we say unintended life transfer, we mean humans unintentionally depositing microbes on to the lunar surface through their spacesuits, a tool or a machine," Graham said.
"Hardiness of these organisms means they can affect future sample analyses to help us understand things like chemical makeup of the regolith (lunar surface material) or the presence of certain organic molecules. Contamination is unavoidable, so we need to track what we're bringing with us so that we can later distinguish lunar chemistry from stuff we brought from Earth," Graham said.
(Reporting by Will Dunham, Editing by Rosalba O'Brien)
