NASA says ‘alien civilisation’ could be found by looking for planet pollution

A NASA scientist has suggested the best way to find alien life on other worlds is to look for pollution caused by "industrialised civilisations" – and he’s developing theories to do just that.

Ravi Kopparapu works for the NASA Goddard Space Flight Center and has suggested unlocking evidence of alien life on other planets would be made easier by looking for pollution being emitted in planet atmospheres.

He suggests that switching search methods for extraterrestrial life to look for evidence of pollution caused by industrial life will increase the chance of discovering other species.

Scientists already search for radio signals, Earth-like climates on other planets and megastructures in an effort to find other lifeforms in the universe.

But searching for atmospheric pollution could be a game-changer in narrowing down the search – as it would suggest the presence of intelligent, business building life.

Science Alert reports that new evidence suggests nitrogen dioxide gas (NO2) emanating from planets would indicate industrialised cultures.

NO2 can be produced by lightning, volcanoes and in other natural ways – but is also caused by the burning of fossil fuels.

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Mr Kopparapu told the outlet: "On Earth, most of the nitrogen dioxide is emitted from human activity – combustion processes such as vehicle emissions and fossil-fuelled power plants.

"Observing NO2 on a habitable planet could potentially indicate the presence of an industrialised civilisation."

Scientists call the presence of NO2 a “technosignature” as it can be used as evidence of technology and the emissions produced by making and using machinery.

It is possible the presence of NO2 could be seen though telescopes by examining how light is absorbed and reflected by the gas.

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Fellow NASA scientist Giada Arney – who works as an astrobiologist – concurs with Mr Kopparapu’s suggestion.

She says: “If we observe more NO2 than our models suggest is plausible from non-industrial sources, then the rest of the NO2 might be attributed to industrial activity.

"Yet there is always a possibility of a false positive in the search for life beyond Earth, and future work will be needed to ensure confidence in distinguishing true positives from false positives."

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