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NASA and private companies like SpaceX want to send people to Mars.
A group of scientists suggest in a new paper that we should infect Mars with Earth's microbes before people land on the red planet.
These microbes could make Mars more suitable for human habitation, the researchers say.
However, this idea runs counter to NASA's policy of protecting planets and other space objects from getting contaminated with Earthly organisms.
Fifty years after humans first stepped onto the moon, Mars has become the next frontier in space exploration.
On Saturday, SpaceX CEO Elon Musk unveiled a rocket prototype called Starship Mark 1: the next step in his company's quest to build a launch system called Starship that could ferry people to the red planet. NASA, meanwhile, plans to send astronauts to Mars in the 2030s.
But for us Earthlings, surviving on a planet with a thinner atmosphere, less gravity, and minuscule amounts of oxygen presents a host of challenges. If people didn't want to spend every second in sealed suits and indoor habitats, they'd need to transform Mars to be more Earth-like. That would require adding oxygen and other gases into the atmosphere to make surface temperatures and air pressure more similar to what we're used to.
A group of scientists from Canada and Brazil says that planetary engineering could be helped along by some unexpected actors: microbes from Earth.
On our planet, microbes like Rhizobium (which converts atmospheric nitrogen to biological nitrogen that can be used by plants) help maintain the gases our atmosphere and drive our food webs. So the scientists suggest that before sending humans to Mars, we should send some microorganisms from Earth there first.
They describe this idea in an opinion paper published in the journal FEMS Microbiology Ecology.
"Life as we know it cannot exist without beneficial microorganisms," Jose Lopez, the lead author of the paper, said in a press release. "To survive on a barren (and as far as all voyages to date tell us) sterile planet, we will have to take beneficial microbes with us."
What microbial settlers could do on Mars
NASA via AP
Scientists estimate that there are 1 trillion microbial species on Earth.
These microscopic organisms played a key role in creating a habitable atmosphere for more advanced lifeforms billions of years ago. They were some of Earth's first denizens, living in the water during a time when our planet was much hotter and lacked oxygen.
"Life on Earth started with relatively simple microorganisms which have the capacity to adapt and evolve to extreme conditions, which defined Earth's habitats in the ancient past," Lopez said.
Since unicellular microbes like cyanobacteria manufactured their own food using photosynthesis, Lopez added, they "provided most of the oxygen we now breathe more than 2 billion years ago."
If introduced to Mars, his team says, bacteria like this could perhaps function similarly — helping to create an Earth-like atmosphere and serving as the foundation of a Martian food chain.
Microbes are still critical for maintaining life on Earth today. They balance gases in the atmosphere and break down animal and plant matter to create the simple substances used at the bottom of food chains. A 2013 study even showed that microbes in the atmosphere contribute to precipitation levels and cloud formation on Earth. Plus, they break down sewage and toxic waste.
"If humanity is seriously contemplating colonizing Mars, another planet, or one of the nearby moons in the future, then people need to identify, understand, and send the most competitive and beneficial pioneers," Lopez and his co-authors wrote.
Another advantage of sending microbes first, the team adds, is that some of the bacteria, viruses, and fungi that support life on Earth are capable of withstanding the harsh environment of space. Scientists call these organisms extremophiles, since they can thrive in Earth's coldest, warmest, and high-pressure environments.
Tardigrades are one example of an extremophile species. They can go without water and oxygen for extremely long periods of time and survive pressures up to 74,000 times the pressure we experience at sea level.
Sending microbes to Mars violates a key tenet of NASA policy
But there's a problem with any effort to seed Mars with microbial invaders from Earth: It would violate NASA's strict guidelines on interplanetary contamination.
The space agency's planetary protection policy aims to prevent our planet from being infected by extraterrestrial life forms, and also to protect other planets and space objects from getting tainted by Earthly life.
Accordingly, all equipment and rockets sent into space are carefully sterilized before leaving Earth. NASA has also destroyed spacecraft to eliminate any risk spreading Earthly contamination in space. The agency's Cassini probe, which started orbiting Saturn in 2004, is a prime example: When Cassini got low on propellant in 2017, scientists opted to send it on a death spiral into Saturn to avoid any possibility that the probe could crash into Saturn's moons Enceladus or Titan. Those moons hide oceans of water and may be habitable to or even host alien life.
Such protections "preserve our ability to study other worlds as they exist in their natural states; to avoid contamination that would obscure our ability to find life elsewhere — if it exists," NASA explains.
The paper authors admit that their suggestion raises some ethical concerns.
"One can rightly argue that microbes released on Mars will represent invasive species that are being introduced into an unexplored and possibly pristine ecosystem," they wrote.
But Lopez and his co-authors said it's inevitable that humanity will contaminate other places in the galaxy.
"We hypothesize the near impossibility of exploring new planets without carrying and/or delivering any microbial travellers," they wrote.
So, they added, we might as well deliberately and systematically choose which microbes we infect Mars with, "rather than sending random bacteria serendipitously hitchhiking."
In that vein, they suggest thinking of Earthly microbes as "assets" that could be critical to kick-starting life on Mars, rather than invaders to be feared.
The researchers suggest choosing Mars-bound microbes carefully
Lopez and his colleagues aren't saying we should send every microbe on Earth into space, though.
"We are not advocating a rush to inoculate," he said.
Rather, they suggest rigorous testing on Earth to determine which extremophiles would have the best chance of making it to and surviving on Mars. These research efforts, his group said, should supersede current endeavors to send people to Mars, since there's no point in trying to settle another planet if we don't have tools to terraform it.
Loren Elliott/Getty Images
That is not the approach Elon Musk and SpaceX are taking, however. Musk wants a fully complete Starship, which could carry dozens of people, to enter Earth's orbit within six months. The ship is designed to eventually carry cargo, and then crews, to Mars by 2023 and 2024, respectively.
"I think we should really do our very best to become a multi-planet species, and we should extend consciousness beyond Earth, and we should do it now," Musk said.