Space Station Experiment Shows Bacteria Could Survive the Long Trip From Earth to Mars

The bacterial exposure experiment took place from 2015 to 2018 using the Exposed Facility located on the exterior of Kibo, the Japanese Experimental Module of the International Space Station.
Credit: JAXA/NASA

Tanpopo mission addresses the possibility of natural interplanetary transport of microbial life called panspermia.

Imagine microscopic life-forms, such as bacteria, transported through space, and landing on another planet. The bacteria finding suitable conditions for its survival could then start multiplying again, sparking life at the other side of the universe. This theory, called “panspermia,” support the possibility that microbes may migrate between planets and distribute life in the universe. Long controversial, this theory implies that bacteria would survive the long journey in outer space, resisting to space vacuum, temperature fluctuations, and space radiations.

“The origin of life on Earth is the biggest mystery of human beings. Scientists can have totally different points of view on the matter. 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. If panspermia is possible, life must exist much more often than we previously thought,” says Dr. Akihiko Yamagishi, a Professor at Tokyo University of Pharmacy and Life Sciences and principal investigator of the space mission Tanpopo.

In 2018, Dr. Yamagishi and his team tested the presence of microbes in the atmosphere. Using an aircraft and scientific balloons, the researchers, found Deinococcal bacteria floating 12 km above the earth. But while Deinococcus are known to form large colonies (easily larger than one millimeter) and be resistant to environmental hazards like UV radiation, could they resist long enough in space to support the possibility of panspermia?

To answer this question, Dr. Yamagishi and the Tanpopo team, tested the survival of the radioresistant bacteria Deinococcus in space. The study, now published in Frontiers in Microbiology, shows that thick aggregates can provide sufficient protection for the survival of bacteria during several years in the harsh space environment.

Dr. Yamagishi and his team came to this conclusion by placing dried Deinococcus aggregates in exposure panels outside of the International Space Station (ISS). The samples of different thicknesses were exposed to space environment for one, two, or three years and then tested for their survival.

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