by As space agencies plan for future manned missions to Mars, and NASA expects humans to set foot on the Red Planet as early as the 2030s, scientists warn that astronauts themselves could be at risk from these missions.
This threat may be alive within their bodies.
New research using simulated conditions on Mars – such as the planet’s lack of water, harsh ultraviolet radiation and exposure to toxic salts – suggests that four types of bacteria that can be carried in the human gut may only survive in Martian soil, or in “regolith,” but, under the right conditions, thrive.
It is a concern that these bacteria — including Burkholderia cepacia, Klebsiella pneumoniae, Pseudomonas aeruginosa and Serratia marcescens — can cause disease in humans. For example, the Centers for Disease Control and Prevention (CDC) states that while B. cepacia can cause a wide variety of symptoms, exposure to the bacteria can lead to serious respiratory infections and that it is already resistant to common antibiotics.
“We looked at four different bacterial species, which are related to humans and have not really been investigated in an environment like Mars,” research team member and German scientist of the Aerospace Center, Tommaso Zaccaria, told Space.com. “We were able to see that these species of bacteria were able to survive, to a certain extent, in certain conditions on Mars – as they were drying out. [loss of moisture]UV radiation and in the atmosphere of Mars.”
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The survival of the bacteria surprised the team. In particular, the researchers did not anticipate how the bacteria reacted to toxic Martian regolith, which was imagined here on Earth to reflect global conditions on the Red Planet rather than a specific area of the planet.
“We thought that the regolith would have a more toxic effect on the bacteria and that it would limit their growth that way,” Zaccaria said. “We did not think that it would completely kill them all, but we thought that it would be more limited. Instead, it seemed that regolith was supplemented with the growth of bacteria.”
The team also determined that not only can the bacteria survive for several days, with P. aeruginosa surviving for a period of up to 21 days, but in certain conditions, they could thrive in Martian soil. Those conditions included access to liquid water and protection from UV light—exactly the conditions that human habitats on Mars must establish for astronauts to survive.
Zaccaria added that this means missions to Mars will need to take medical precautions, such as carrying extra antibiotics, to protect people on the Red Planet from bacterial threats brought from home.
Download the hunt for life on Mars
Despite the bacteria surviving in Mars-like conditions, the reliance on very specific conditions to survive means that the organisms are unlikely to colonize the Red Planet after being transported from Earth. “The growth would be very limited,” declared Zaccaria.
That doesn’t mean there isn’t cause for concern, however.
“We still think it is very important to protect Mars, and we want to draw attention to the fact that there should be certain mission planning to take these types of bacteria into account as well,” said Zaccaria. “We don’t want to contaminate Mars with human-related bacteria.”
Currently, NASA’s Curiosity and Perseverance rovers are exploring ancient, dried-up lake beds on Mars to look for signs that simple, bacteria-like life may once have existed on the nascent world.
However, this new research suggests that if people were to explore such regions in person, they could carry unwanted bacteria with them and cause contamination. This bacterium could also mutate under Martian conditions, making it difficult to identify them as being from Earth. And this it can lead to some confusion that prevents us from determining whether signs of life found on Mars came from the Red Planet or took a trip from our own home.
“If a particular location on Mars were of astronomical interest, robotic missions that could easily sterilize but less contain human bacteria might not be allowed to go there,” Zaccaria said. “This could classify certain areas of Mars as regions similar to national parks that we have here on Earth.”
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Zaccaria also said that because the human immune system functions differently in the microgravity of space, the exact effect the four bacteria would have on human health on Mars cannot be predicted at the moment. This is an investigation that he and his colleagues at the German Aerospace Center will carry out in the future.
In addition, the researchers will investigate how other bacteria cope with Mars-like conditions.
“Maybe some bacteria would be more tolerant to the conditions on Mars, and they will resist for longer periods of time, or maybe they are not so resistant,” said Zaccaria. “It will be interesting to evaluate other types of bacteria associated with humans, which do not necessarily cause disease, but can be carried by the human microbiome on the skin or inside the human body, to Mars.”
The team’s research was published in January in the journal Astrobiology.
