Our Planet's "BioFingerprint" Discovered: Search for Earth's Twin Just Got Easier

"Detecting Earth in reflected light is like searching for a firefly from a searchlight that is 2,400 miles distant," according to a panel of astronomers describing the challenges facing the search for other planets in the universe.

With a dramatic new advance, however, astronomers have confirmed an effective way to search the atmospheres of planets for signs of life, vastly improving our chances of finding alien life outside our solar system. Think of it as the method to discover the Earth's "fingerprint" -information about the chemical composition of the Earth’s atmosphere from sunlight that has passed through it.

A team from the Instituto de Astrofisica de Canarias used the William Herschel Telescope on La Palma and the Nordic Optical Telescope to take the first transmission spectrum of the Earth.

When a planet passes in front of its parent star, part of the starlight passes through the planet’s atmosphere and contains information about the constituents of the atmosphere. Even though astronomers can’t use exactly the same method to look at the Earth’s atmosphere, the team was able for the first time ever to gain a spectrum of our planet by observing light reflected from the Moon towards the Earth during a lunar eclipse.

The spectrum not only contained signs of life but these signs were unmistakably strong. It also contained unexpected molecular bands and the signature of the earth ionosphere.

“Now we know what the transmission spectrum of a inhabited planet looks like, we have a much better idea of how to find and recognize Earth like planets outside our solar system where life may be thriving," said Enric Palle, of the Instituto de Astrofisica de Canarias. "The information in this spectrum shows us that this is a very effective way to gather information about the biological processes that may be taking place on a planet.”

“Many discoveries of Earth-size planets are expected in the next decades and some will orbit in the habitable zone of their parent stars. Obtaining their atmospheric properties will be highly challenging; the greatest reward will happen when one of those planets shows a spectrum like that of our Earth,” added Pilar Montañes-Rodriguez, of the Instituto de Astrofisica de Canarias.

The research was published in the 11th June issue of Nature .

Posted by Casey Kazan.

http://www.scitech.ac.uk/PMC/PRel/STFC/transmissionspectrum.aspx

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