Astrobiologists look for extraterrestrial life by searching for gases (i.e. methane and oxygen) that suggest the possibility of life, or for radio or laser signals in the hopes of communicating with distant alien life forms. But now a team of astronomers at Harvard is suggesting we also look for gases not generated by biological processes—read: industrial air pollution. The James Webb Space Telescope, launching in 2018, could detect pollutants like chlorofluorocarbons (used in air conditioning and refrigerators) so long as they exist on a planet near a white dwarf (the remains of a sun-like star) because light from a burning sun would interfere with the ability to see the chemicals, reports LiveScience.
Greenhouse gases could even be a sign of primitive life. "We consider industrial pollution as a sign of intelligent life, but perhaps civilizations more advanced than us ... will consider pollution as a sign of unintelligent life since it's not smart to contaminate your own air," the study leader says in a statement. If we detect such chemicals, they could potentially lead to dead civilizations—or ones that found a way to use greenhouse gases for warmth, says Avi Loeb, chair of Harvard’s astrophysics department and a co-author of the paper. Loeb tells Time he's surprised that no one has yet thought to look for industrial air pollution. Finding it may be a long shot, but as physicists have said about looking for alien radio signals, "If we never search, the chance of success is zero.” (Meanwhile, extraterrestrial life may be closer to home than we think.)