Could we find alien life via its pollution?

Could we find alien life via its pollution? But one day about 10 years ago, a colleague knocked on Gonzalo González Abad's door and asked him an unexpected question: "If you were looking for traces of a technologically advanced alien civilisation, light years away from us, how would you try to do it?" "Most of the NO2 on our planet comes from industrial activity," says Giada Arney of Nasa Goddard Space Flight Center, who co-authored a 2021 study on the potential for discovering alien civilisations by searching the galaxy for NO2 pollution. "One might also think about temporal technosignatures that could give you additional information about what's going on in the planet's atmosphere," says Arney. Getty Images Some human-made chemicals - like ozone depleting chorofluorocarbons - have effects which can last hundreds of years Besides the short life of NO2, however, there's also the issue that there are quite a lot of natural sources that produce it – from lightning to wildfires, so finding it might not be hard proof that an alien civilisation had developed internal combustion engines, for instance, or any other NO2-spewing technology.