A team of NASA scientists is taking a clever approach to hunting for alien life: scanning exoplanets for signs of air pollution.
Just as pollutants like nitrogen dioxide and greenhouse gases in Earth's atmosphere are an indication of human activity below, a team of NASA researchers are now looking for pollutants on other, potentially-habitable exoplanets as a new alien technosignature, meaning a sign of an advanced extraterrestrial civilization. Their study, posted online and accepted for publication in The Astrophysical Journal, is the first to add nitrogen dioxide as a potential technosignature — giving scientists a new tool in the search for life.
The idea of sniffing out aliens based on their pollution isn't a new one. But adding nitrogen dioxide, a byproduct of burning fossil fuels in power plants or vehicle engines, helps broaden the search.
"Therefore, observing [nitrogen dioxide] on a habitable planet could potentially indicate the presence of an industrialized civilization," lead study author Ravi Kopparapu, a researcher at NASA's Goddard Space Flight Center, said in a press release.
The problem is that many worlds might have naturally-occurring nitrogen dioxide in their atmospheres, especially since it can be given off by volcanic activity. So part of the new study was finding a way to model the amount of nitrogen dioxide there should be on a given exoplanet.
"If we observe more [nitrogen dioxide] than our models suggest is plausible from non-industrial sources," study coauthor and Goddard researcher Giada Arney said in the release, "then the rest of the [nitrogen dioxide] might be attributed to industrial activity."
More on technosignatures: NASA Funds Harvard Hunt for Alien “Technological Civilizations”