A new experiment has shown that bacteria are capable of surviving the harsh conditions of space for long periods. This supports the possibility that life on Earth may have started in space.
As part of the Tanpopo space mission, a team of Japanese researchers sent samples of microbial life up to the International Space Station (ISS). While aboard the ISS, the samples were exposed to the vacuum of space for up to three years at a time. The purpose of the study was to investigate the validity of the Panspermia hypothesis.
What is Panspermia?
Panspermia is the theory that life on Earth originated from microorganisms that arrived from outer space, travelling on meteors, comets or other forms of space debris. After falling to Earth, this bacteria multiplied and evolved over four billion years into the life we see all around us today.
More broadly, panspermia theory predicts the existence of bacteria throughout the universe living on comets and meteoroids, resistant to the harsh conditions of space. Although first mentioned in the 5th-century BC by Greek philosopher Anaxagoras, panspermia theory gained most of its scientific attention in the mid-1800s when it was proposed by notable scientists such as Lord Kelvin, Hermann von Helmholtz and Jöns Jacob Berzelius.
If other life currently exists in space it is very likely to be in the form of bacteria, so the idea of our microbial origin being from space seems plausible to many. Panspermia remains a popular hypothesis today among astrobiologists for explaining the origin of life on Earth.
The Tanpopo Mission
Between 2015 and 2018, bacteria known as Deinococcus was exposed to the vacuum of space on the exterior of Kibo, the Japanese experimental module on the ISS. For up to three years, the bacteria was subject to the harsh conditions 400 kilometres above the Earth’s surface.
These conditions included intense ultraviolet (UV) radiation, large temperature fluctuations and the lack of any oxygen or nutrients.
The results after three years were very promising for advocates of panspermia theory. Dr. Akihiko Yamagishi, lead investigator of the mission, and his team found that every bacteria colony larger than 0.5 millimetres in size partially survived in space.
A large bacterial cluster (called an aggregate) formed over time. While the bacteria on the surface of the aggregate died, it created a protective shield for the bacteria underneath, ensuring that the colony survived.
Using the data collected, the researchers were able to predict that a colony of bacteria larger than 0.5 mm could potentially survive between 15 and 45 years on the ISS. If the colony is larger than 1 mm in diameter it could survive for up to 8 years in outer space, where the conditions are even more harsh.
“The results suggest that radio-resistant Deinococcus could survive during the travel from Earth to Mars and vice versa, which is several months or years in the shortest orbit,” explained Dr. Yamagishi.
The importance of the findings
Dr. Yamagishi commented on the importance of the mission:
“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.”
This research shows that microorganisms are capable of surviving in space without protection, whether it be travelling on a comet, meteor or otherwise. More than this, it gives credibility to the possibility that life on Earth began as bacteria in space.
So, if bacteria in space is common, what other distant worlds may it have landed on in the past? And is panspermia truly the way life spreads throughout the universe? Perhaps our intergalactic cousins are asking the same question right now.
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