Is there anybody out there?: An artist's impression of an Earth-like alien world bombarded with meteorites.

Credit: NASA

Bigger and better: NASA's terrestrial planet finder has the right equipment, but just isn't big enough.

Credit: NASA

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SYDNEY: Large space telescopes could zoom in on the atmospheres of planets around other stars, helping to speed up the search for extraterrestrial life, says a new study.

A new space-based telescope costing about A$12.3 billion (US$10 billion) could detect alien life on extrasolar planets using technology already available today, said Steve Beckwith, author of the report and astronomer at the University of California, Berkeley.

He said that methods, such as observing the change in light from a star as a planet passes in front, or blocking the light from stars and focussing on the faint light of their planets instead, could reveal tell-tale traces of oxygen, carbon dioxide, methane and water vapour in the planets’ atmospheres. These could then be analysed for clues to alien life.

A price worth paying?

Though over 300 extrasolar planets have been found to date, only one has been found within the habitable zone of its star (see, New Earth-like planet may hold liquid water, Cosmos Online). This zone is the favourable region of space around a star that is though to have encouraged life on Earth.

Beckwith’s research, published this week in the Astrophysical Journal, calculates the technical requirements needed to detect the chemical signatures of life in the light spectrum of Earth-like planets when viewed from across the galaxy.

One of the most useful techniques for this sort of search is coronagraphy, said Beckwith. Coronagraphs were originally invented to study the Sun's corona (its atmosphere), but they are also capable of blocking the light from bright stars to allow us to observe their planets more clearly.

However, projects currently in the pipeline to observe extrasolar planets, such as NASA’s Terrestrial Planet Finder’s coronagraph, due for launch in 2014, don’t have sufficiently large apertures, he said. The consequence being that planets of interest might end up spending the majority of their time behind the part of the instrument used to block the light of the star, he said.

To spot life-bearing planets effectively, there is a need for larger, space-based telescopes with diameters of eight to ten metres, said Beckwith, the downside being the great expense. “But considering the amount we routinely spend on other sectors of the government and the excitement that would result from the first discovery of extra-terrestrial life, it is a sum that society may well want to spend,” he told Cosmos Online.