Despite our best efforts to find signs of alien life in the universe, our search has come up empty.

Where we look for these signs is constantly evolving, and the latest discovery could have major implications in our analysis of other planets.

In a paper published to the Journal of the Royal Society Interface , a team from the University of York has announced the very first observation of living bacteria in polar ice and snow, an environment that science had believed to be completely sterile.

Climate scientists have long used polar ice as a source for information on our planet’s history due to pockets of CO2 that have been trapped over millennia, which can then be compared with current levels in the industrial age.

Until now, researchers had presumed that these samples could be considered unaltered as the ice would be devoid of life that could alter CO2 levels, but the new research shows this is not the case.

Implications for climate data

“As microbial activity and its influence on its local environment has never been taken into account when looking at ice-core gas samples, it could provide a moderate source of error in climate history interpretations,” said lead author Dr Kelly Redeker.

“Respiration by bacteria may have slightly increased levels of CO2 in pockets of air trapped within polar ice caps, meaning that before human activity, CO2 levels may have been even lower than previously thought.”

Redeker added: “In addition, the fact that we have observed metabolically active bacteria in the most pristine ice and snow is a sign of life proliferating in environments where you wouldn’t expect it to exist.

“This suggests we may be able to broaden our horizons when it comes to thinking about which planets are capable of sustaining life.”

Searching icy moons

The first sign that bacteria was present in the samples came after Redeker and his team sterilised a number of ice samples using UV lamps and then compared them to ones that remained untouched.

When they compared the results, the team found unexpected levels of methyl iodide – a gas known to be produced by marine bacteria – in the untouched snow.

Our understanding of the durability of bacteria has been known to science for some time, as seen in tiny creatures called tardigrades , which survived being blasted into space.

But this study is the first time that bacteria have been observed altering the polar snow environment in situ, and it offers a new line of investigation for astrobiologists to find signs of alien microbial life in vast icy worlds such as Enceladus.

Colm Gorey

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