Pollution Helps for Search of Alien Life

Researchers are using pollution to help in their search for alien life on other worlds, as described in a study published in The Astrophysical Journal. By observing exoplanet atmospheres, scientists can look for gases like oxygen and methane that only coexist if replenished by life.

The research team offers a new approach in the search for extraterrestrial intelligence (SETI).

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

"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," joked co-author Avi Loeb.

Using the upcoming James Webb Space Telescope (JWST), researchers should be able to detect two kinds of chlorofluorocarbons (CFCs) - ozone-destroying chemicals used in solvents and aerosols.

JWST could potentially tease out the signal of CFCs if atmospheric levels were 10 times those on Earth. The study team also speculates that a more advanced civilization might intentionally pollute its own atmosphere in order to globally warm a planet that is otherwise too cold for life.

However, one snag in this approach is that it overestimates the capabilities of JWST. The telescope can only detect pollutants on an Earth-like planet circling a white dwarf star, which is what remains when a star like our Sun dies. A next-generation telescope would be needed to complete this work.

The team notes that a white dwarf might be a better place to look for life than previously thought, since recent observations found planets in similar environments.

And this methodology could not only find existing polluting planets, but past ones too. Some pollutants last for 50,000 years in Earth's atmosphere while others last only 10 years.

"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 said.