The Best Way to Find Aliens on Other Worlds May Be to Search For Signs of Their Smog 14 FEBRUARY 2021 The Universe is a big place, so scientists are keen to narrow down their search for alien life – maybe by looking for radio signals, or hospitable climates, or huge megastructures. Now another sign of alien life is under consideration: atmospheric pollution.
If there are alien civilisations out there, the hypothesis goes, then their activities and industries may have produced pollution just like ours have. That pollution could be something we could spot in our scans of deep space. A new study suggests nitrogen dioxide gas (NO2) could indicate life on other planets: It can be produced from burning fossil fuels, as well as from lighting, volcanoes, and other biological, non-industrial sources.