polluted exoplanet
July 24, 2014

Using Pollution To Locate Extraterrestrial Life

redOrbit Staff & Wire Reports - Your Universe Online

Industrial pollution could help in the Search for Extraterrestrial Intelligence (SETI), claim Harvard-Smithsonian Center for Astrophysics (CfA) researchers who have started looking for signs of pollutions on other worlds.

According to the study authors, by studying exoplanet atmospheres, scientists can look for gases such as oxygen and methane that only exist together if they are replenished by microbial life. In addition, they theorize that advanced civilizations could leave behind evidence of their existence by spewing industrial pollution into the air.

“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,” lead author Henry Lin said in a statement.

Lin, a student at Harvard, and his colleagues predict that looking for pollutants could offer a new approach in the hunt for alien lifeforms. They report that the upcoming James Webb Space Telescope (JWST) could be capable of detecting two types of chlorofluorocarbons (CFCs) – ozone-destroying chemicals used in solvents and aerosols.

Based on their calculations, the JWST telescope could pinpoint CFC signals if atmospheric levels were 10 times that on Earth. A particularly advanced civilization, on the other hand, could intentionally cause high levels of atmospheric pollution in order to warm a planet that would otherwise be too cold to support life, Lin and his co-authors explain in research accepted for publication in The Astrophysical Journal.

“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. We point out that in addition to these generic indicators, anthropogenic pollution could be used as a novel biosignature for intelligent life,” they wrote.

Their research focused on tetrafluoromethane CF4 and trichlorofluoromethane (CCl3F), which they said are the easiest-to-detect CFCs that are produced by anthropogenic activity. They went on to estimate that between 1.2 and 1.7 days of total integration time to detect CCl3F (CF4) concentration up to 10 times current terrestrial levels.

Which brings us to one of the limitations of their research: the JWST telescope is only capable of detecting pollutants on an Earth-like planet orbiting around a white dwarf star, which is what will remain of the Sun once it dies. Detecting pollutants on an Earth-like planet traveling around a Sun-like star would require a more powerful instrument.

“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. Those planets could have survived the bloating of a dying star during its red giant phase, or have formed from the material shed during the star's death throes,” the university said.

While it is possible that searching for CFC could help locate a thriving extraterrestrial civilization, it could also locate the remnants of an alien society that had been wiped out. After all, since some pollutants can survive in Earth’s atmosphere for up to 50,000 years, detecting these types of molecules without also finding evidence of more short-lived pollutants would indicate that the creatures that created them were no longer around.

“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,” said co-author Avi Loeb.

From the Nasa Technical Reports Server (Ntrs) The James Webb Space Telescope Mission by Matthew a. Greenhouse