The Search for Extraterrestrial...Pollutants?

In addition to monitoring for radio signals from alien worlds, another way of searching for extraterrestrial life might be to look at planets in certain types of solar systems for pollution:

Avi Loeb, an astronomer at Harvard University. [has] a new suggestion based on his experience here on Earth. Scan the skies for little, brown men - the chronic polluters. Astronomers have been able to glimpse the atmospheres of planets outside our solar system for a while now. And there's a new space telescope scheduled for launch in 2018 that Loeb says, he could use.The idea would be that when a planet like the Earth is passing in front of its host star a small fraction of the light from the star would pass through the atmosphere and show - potentially - evidence for these pollutants.

Certain pollutants don't occur naturally. So if astronomers saw them that would point to industrial activity on the planet. And that would indicate intelligence. Loeb has published some calculations in the exciting, September issue of the astrophysical Journal Letters. They showed that if the new telescope looks at the right kind of star, the pollution will be detectable if it's 10 times bigger than in the Earth's atmosphere.

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