Scientists Prove That Human Gut Bacteria Can Survive a Trip to Space Without Us

Space travel is not for the weak. Astronauts endure motion sickness, disorientation, cardiovascular stress—and that’s before they even reach orbit. Luckily, the bacteria that lives inside us is far more resilient. A new study shows that a gut bacteria essential for human health can survive the stress of being launched into space aboard a rocket, the microgravity environment, and reentry into Earth’s atmosphere.

A group of scientists in Australia launched spores of Bacillus subtilis, a gram-positive bacteria that lives in our intestinal tracts, to the edge of space to see how the microbes fared. Upon examination after the bacteria had returned to Earth, the scientists found the microbes had experienced no change in their ability to grow and that their structure remained intact.

The findings are detailed in a study published Monday in npj Microgravity. The work indicates that the bacteria would likely work as needed inside the guts of any humans on their way to Mars—crucial information for astronaut health. But it also suggests that human-led contamination of Mars with Earthly bacteria may be inevitable.

Space-faring bacteria

Previous experiments on board the International Space Station (ISS) have shown that certain types of bacteria can survive in space. There hasn’t been much research done, however, on the effects of a rocket launch and reentry on the survival rates of human gut bacteria.

In order to put the bacteria to the test, the researchers packed spores on board a sounding rocket and launched it to an altitude of around 160 miles (260 kilometers) above the surface of Earth. During the second stage burn, the rocket experienced a maximum acceleration of 13 G (or 13 times the force of Earth’s gravity).

Once it reached its desired altitude, the researchers initiated a brief period of weightlessness that lasted for around six minutes as the main engine shut off. After that, the rocket began its descent to Earth, decelerating at forces up to 30 G while spinning at a rate of 220 times per second.

After the grueling journey, the researchers examined the bacteria spores to see how they fared during the rocket launch and reentry. Surprisingly, the bacteria showed no change to their structure, nor did the extreme forces affect its ability to grow.

“Our research showed an important type of bacteria for our health can withstand rapid gravity changes, acceleration and deacceleration,” Elena Ivanova, a professor at the Royal Melbourne Institute of Technology in Australia, and co-author of the study, said in a statement. “It’s broadened our understanding on the effects of long-term spaceflight on microorganisms that live in our bodies and keep us healthy. This means we can design better life support systems for astronauts to keep them healthy during long missions.”

The idea of bacteria surviving and thriving on their way to the Red Planet, however, isn’t always met with enthusiasm. The findings follow a separate study published last year which warned bacteria not only have the potential to survive a trip to Mars, but also feel right at home in the Martian soil. As space agencies plan for human missions to Mars, there is growing concern that those missions could contaminate the Martian environment with out Earthly microbes. That could lead to mistaken discoveries of life on the planet, but it could also pose an immediate risk to the astronauts themselves—or indeed, any life that might be on Mars in the first place.