In the search for “little green men,” astronomers may want to focus on extraterrestrials that aren’t too green. A team suggests looking for industrial pollution in the atmospheres of distant planets as a signpost for intelligent life – assuming, of course, that pollution is a hallmark of intelligence.
As the tally of known planets beyond our solar system grows –it’s up to about 1,800 – the search for life beyond Earth drifts away from science fiction and toward the realm of possibility. Radio astronomers routinely scope out newfound solar systems for hints of engineered signals. Observations at other wavelengths of light are revealing the environments on these distant worlds.