A group of scientists say they might have found a way to detect if alien life exists on faraway planets. First, however, they’ll have to find out if extraterrestrials pollute as much as the inhabitants of Earth.

The crux of a paper published in the latest edition of the Astrophysical Journal Letters relies on the theory that, should aliens exist, then perhaps they could be discovered here on Earth by using a high-tech telescope able to monitor space for certain gasses expected to be emitted by distant civilizations.

Theorists at the Harvard-Smithsonian Center for Astrophysics say that the James Webb Space Telescope being developed by NASA should allow scientists to see deep into space and scour the universe for evidence of certain substances.

“By studying exoplanet atmospheres, we can look for gases like oxygen and methane that only coexist if replenished by life. But those gases come from simple life forms like microbes. What about advanced civilizations? Would they leave any detectable signs?” the scientists ask. “They might, if they spew industrial pollution into the atmosphere.”

“Detecting biosignatures, such as molecular oxygen in combination with a reducing gas, in the atmospheres of transiting exoplanets has been a major focus in the search for alien life,” the scientists say in their abstract. Additionally, they argue, “anthropogenic pollution could be used as a novel biosignature for intelligent life,” specifically the kind of pollution that could be picked up by the still-in-development telescope.

In other words, the scientists say that alien life could be uncovered if the NASA telescope, or future, more powerful models, can detect distant pollution that it would be impossible to blame on humans, but rather would presumably be the byproduct of extraterrestrial civilization.

“On Earth, atmospheric pollution has been carefully studied in the context of global climate change and air quality concerns,” the researchers write in their six-page paper. “It is ironic that high concentrations of molecules with high global warming potential (GWP), the worst-case scenario for Earth's climate, is the optimal scenario for detecting an alien civilization, as GWP increases with stronger infrared absorption and longer atmospheric lifetime.”

"People often refer to ETs as 'little green men,' but the ETs detectable by this method should not be labeled 'green' since they are environmentally unfriendly," co-author Avi Loeb, an astrophysicist at Harvard, said in a statement this week.

On the other hand, Loeb adds that any advanced life forms that have yet to be discovered might be advanced enough to be beyond creating space pollution.

"We consider industrial pollution as a sign of intelligent life, but perhaps civilizations more advanced than us, with their own SETI [Search for extraterrestrial intelligence] programs, will consider pollution as a sign of unintelligent life since it's not smart to contaminate your own air," added Harvard student and lead author Henry Lin.

"In that case, we could speculate that the aliens wised up and cleaned up their act. Or in a darker scenario, it would serve as a warning sign of the dangers of not being good stewards of our own planet," Loeb added.