Space travel has fascinated the public since the space race of the 1960s. Ideas of survival outside of the Earth’s atmosphere captivate public interest and raise questions about whether life could spread and thrive in such extreme conditions. Some astrobiologists experiment with the survival of different organisms in intense space environments, working to understand if life could ever be transferred from one planet to another. To answer questions like these, astrobiologist Yuko Kawaguchi and his colleagues investigated experiments with bacteria sent through space to understand whether and how they could survive this challenging travel.
Starting in 2015, NASA astronaut Scott Kelly began attaching Deinococcus bacteria, a radiation-resistant bacterial strain, to the outer walls of the International Space Station. Stuffed in their own personal space pod, a small well in a metal plate, the groups of bacteria were blasted off to space. A small percentage was able to survive a three-year-long stint in space from their release in 2015 until the samples were analyzed in 2018. The key to the 4% survival rate was the use of the dead outer cells as cover for the surviving living bacteria. Researchers experimented with bacteria pellets, conglomerates of bacteria stuffed into the same metal plate, of varying thickness: 100 micrometer (μm), 500 μm and 1,000 μm. All microbes in the 100 μm pellet, a diameter no thicker than a human hair strand, suffered extensive DNA damage. In the 500 and 1,000 μm pellets, the DNA in the outer cells also all succumbed to radiation damage, but these thick outer dead cell casings then acted as a shield to protect inner bacteria from the harsh space environment. Kawaguchi and his colleagues hypothesize that these surviving microbes, protected by their outer cover, have the potential to spread life throughout the universe.
The lifespan of these bacteria in space suggests they may have the potential to reach as far as Mars and lead to the beginnings of life outside the realms of Earth. There are different mechanisms proposed for how microbes such as these may be expelled into space, but once present this is evidence they could survive a cosmic adventure that humans can only imagine. Scientists are still trying to figure out if, after the trip itself, organisms would thrive in different planetary atmospheres and how the survival rates could be impacted. The results of this investigation provide convincing preliminary evidence that bacteria could act as an voyager for the interplanetary transfer of life. With further research, the full scope of organismal survival in the abyss of space may one day be possible.
Dr. Yuko Kawaguchi is an astrobiologist at the Tokyo University of Pharmacy and Life Sciences in Hachioji, Japan. This research was assisted by 16 other researchers and faculty members from partner institutions across Japan.
Managing Correspondent: Samantha Tracy
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