AsianScientist (Aug. 28, 2020) – By clumping together to form aggregates, UV-resistant bacteria could possibly survive in space for up to eight years. These findings, published in Frontiers in Microbiology, are based on data collected on the Tanpopo space mission in 2018.
The ‘panspermia’ theory posits that life was sparked by extraterrestial microbes that somehow found their way to Earth. Long controversial, this theory implies that bacteria can survive the long journey in outer space, resisting vacuum, temperature fluctuations and space radiation.
“Scientists can have totally different points of view on the origin of life on Earth. Some think that life is very rare and happened only once in the Universe, while others think that life can happen on every suitable planet,” said Dr. Akihiko Yamagishi, a professor at Tokyo University of Pharmacy and Life Sciences. “If panspermia is possible, life must exist much more often than we previously thought.”
To see if bacteria might be able to survive in space, Yamagishi and his team tested the presence of microbes in the atmosphere. Using an aircraft and scientific balloons, they found Deinococcal bacteria floating 12 km above the earth. While Deinococcus are known to form large colonies and be resistant to environmental hazards like UV radiation, it was not known if they could survive long enough in space to support the possibility of panspermia.
To answer this question, Tanpopo team tested the survival of Deinococcus bacteria in space. They first placed dried Deinococcus aggregates on exposure panels outside the International Space Station. Samples of different thicknesses were exposed to space environment for one, two or three years and then tested for their survival.
After three years, the researchers found that all aggregates larger than 0.5 mm partially survived to space conditions. Observations suggest that while the bacteria at the surface of the aggregate died, they created a protective layer for the bacteria beneath ensuring the survival of the colony.
Using the survival data, the researchers estimated that a pellet thicker than 0.5 mm would have survived between 15 and 45 years on the ISS. The design of the experiment allowed the researchers to extrapolate and predict that a colony of 1 mm of diameter could potentially survive up to eight years in outer space conditions.
“The results suggest that radioresistant Deinococcus could survive during the travel from Earth to Mars and vice versa, which is several months or years in the shortest orbit,” said Yamagishi.
This work provides the best estimate of bacterial survival in space to date, the authors said. While previous experiments prove that bacteria could survive in space for a long period when benefitting from the shielding of rock (i.e. lithopanspermia), this is the first long-term space study raising the possibility that bacteria could survive in space in the form of aggregates.
Nonetheless, the authors note that microbe transfer also depends on other processes such as ejection and landing, during which the survival of bacteria still needs to be assessed.
The article can be found at: Kawaguchi et al. (2020) DNA Damage and Survival Time Course of Deinococcal Cell Pellets During 3 Years of Exposure to Outer Space.
Source: Frontiers; Photo: JAXA/NASA.
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#Bacteria #Fukuoka Institute of Technology #International Space Station #Japan #Japan Aerospace Exploration Agency #Microbiology #Nagaoka University of Technology #National Institutes for Quantum and Radiological Science and Technology #Osaka University #Space Science #Tokyo University of Pharmacy and Life Sciences