Kimiya Yui helped set up the module for exhibition experiments on the International Space Station back in 2015.
JAXA / NASA
Space is not friendly to humans. Even in the International Space Station, Scientists have shown prolonged flight can lead to some negative effects on health and mess with DNA. But if you are a microscopic organism, things can be a little different.
In fact, some molds that have made a home on the ISS even find the conditions preferable – they can feed on the extra radiation. This kind of evidence has led some scientists to suggest that microscopic organisms could be emitted into space, and perhaps they could move between planets, spreading life across the cosmos.
It’s a controversial concept known as “panspermia”, and it has been crowned by some unusual characters in the past as an alternative theory for how life began.
In a new study published in the journal Frontiers in Microbiology, Japanese researchers sent sealed balls of bacteria to the International Space Station and placed them on the outside of the lab, where they were exposed to the harsh, cold and radiant vacuum. of space.
The experiment, known as Tanpopo, has been running since 2015. In Japanese, tanpopo means dandelion, and the experiment is so named because the dandelion spreads its seeds through the wind. Could the same thing happen in space, with radiation-resistant bacteria? That was the question Akihiko Yamagishi, an astrobiologist at Tokyo University of Pharmacy and Life Science, set out to answer back in 2007, when his experiments were first accepted as a candidate experiment on the ISS.
Yamagishi does not see himself as a proponent of panspermia, but wanted to see if there were ways in which microbes could survive a journey from Earth to somewhere else in the cosmos.
When the Japanese space agency Experiment Handrail Attachment Mechanism was installed on the ISS in 2015, Yamagishi and his team finally had a chance to conduct their research. By placing colonies of the radiation-resistant Deinococcus in wells and drying the suspensions in the air over and over again, they were able to make “pellets” of bacteria. In 2015, these pellets were installed on the space station in plates aboard the ExHAM.
Competitor experiments were designed to look at the pellets after one, two and three years. The experiment was officially completed in 2018 and since then, the Yamagishi team has been analyzing the data.
The main finding shows that these pellets can survive damage caused by UV radiation in space much better if the pellets were thicker. When the pellets were about half a millimeter thick, the outer layers of bacteria began to break, but those in the center survived. Yamagishi and his team argue that these thicker pellets of bacteria, exposed to interplanetary space, may survive for two to eight years – in theory, long enough to emerge from Earth and make it to one of our closest neighbors.
“The results suggest that radioresistant Deinococcus could survive during the journey from Earth to Mars and vice versa, which is several months or years in the shortest orbit,” Yamagishi said.
Bacterial astronauts
Proponents of Panspermia suggest that some bacteria may be able to trap interplanetary travel in meteorites and micrometeorites, a theory known as lithopanspermia. Yamagishi’s work looked at another theory – that these ball-like colonies of bacteria could protect themselves. This is known as mass pan spermia.
But there are a number of persistent problems. A direct shot from Earth to Mars is not exactly the most likely route that microbial adventurers can take.
“In theory, time could be months or years, if you stick to it a ride aboard the Mars Perseverance rocket, “says Brendan Burns, an astrobiologist at the University of New South Wales who did not join the study.” But in terms of ‘natural’ travel, there is a chance that an object will be ejected from Earth and hit Mars in a short time. “
While Yamagishi’s research demonstrates the ability of bacteria to survive space for extended periods, Burns notes that meteorites can have a flight time of more than 10 million years before they orbit planets.
And there’s a pretty big problem to overcome if you’re microscopic and trying to move from planet to planet. First, you need to be expelled from your home planet without dying, the long (really long) travel across space and then make it through an atmospheric reload. Even though NASA robots are afraid to enter the atmosphere of Mars.
Yamagishi agrees. “Very little is known about entry and exit,” he says.
But let’s say Deinococcus got it all, what happens when the bacteria come to their new home? The situation is probably difficult for an earth transplant, accustomed to a world of running water and protected by a thick atmosphere.
“Even if a particular lifeform could survive interplanetary travel, the circumstances in which it ends must be just right to begin anew,” says Burns. He notes that the microbes must be looking for nutrients and should be hard enough to resist differences in the atmosphere. So while the panspermia hypothesis remains possible, Burns says, “the jury is still very out.”
The Yamagishi team and the Tanpopo mission will conduct exhibition experiments “with different species in different conditions” and hope to see how general the process of mass panpermia can be.
