Everyone knows that space isn’t kind to the human body. However, smaller organisms—like bacteria and certain fungi—are able to survive in the void. In fact, some of these species actually thrive in outer space thanks to their ability to feed on extra radiation.
Scientists believe these hearty characteristics support the fact that microscopic organisms could survive a journey across the cosmos to another planet—a concept known as panspermia. For instance, a trip between Earth and Mars.
While a recent International Space Station (ISS) experiment proved that bacteria are certainly able to survive in space for several years, the odds of a clump of microbes completing an interplanetary journey are slim.
Years in the Making
Akihiko Yamagishi, an astrobiologist from the Tokyo University of Pharmacy and Life Science, set out to solve the mysteries of whether bacteria could survive in space. An experiment called Tanpopo (Japanese for dandelion) began in 2015. Researchers sent densely-packed balls of radiation-resistant Deinococcus bacteria to the ISS.
When the Japanese space agency installed its Experiment Handrail Attachment Mechanism in 2015, those colonies were also fastened to the exterior of the space station. The experiment, which officially concluded in 2018, has given Yamagishi’s team plenty of data to analyze.
Recently, the researchers published the results of their study in the journal Frontiers in Microbiology.
The team found that the clusters of bacteria were able to survive damage from space’s plentiful UV radiation as well as starvation from a lack of nutrients. Pellets of bacteria that were thicker served as a sort of nest. The outer layers of started breaking down while the microbes in the center survived.
Yamagishi concludes that these thick clusters of bacteria could, in theory, survive in space for two to eight years. That’s plenty of time for the Deinococcus clumps to make it from Earth to Mars.
Scientists who support panspermia typically suggest that bacteria could travel to other planets aboard a meteorite. Unfortunately for the bacteria clusters, interplanetary travel on a meteorite isn’t as fast as traveling in a rocket.
Brendan Burns, an astrobiologist from the University of New South Wales who isn’t affiliated with the study, says, “In terms of ‘natural’ journeys the likelihood of an object ejected from Earth and hitting Mars in a short space of time is slim.”
He also notes that meteorites can potentially fly for millions of years before reaching a new planet. So, while clumps of space bacteria can survive for an extended period, they’d have almost no chance of making it to another planet alive.
There is also another problem. Even if bacteria pellets did survive an improbable journey to Mars, the environment there is equally hostile. With no running water or reliable nutrient sources, bacteria clusters from Earth would have a hard time surviving—let alone thriving—on a planet that differs from home.
Burns says, “Even if a given lifeform could survive interplanetary travel, the conditions of where it ends up must be just right for it to take off again.”
With all of this in mind, bacteria journeying to new planets without human help seems unlikely. Of course, the findings of Yamagishi’s study are relevant for future space travelers. Astronauts will need to be careful about contaminating future lunar bases or Mars habitats with hitchhiking bacteria from Earth.