First Methane Spotted on Distant Planet

The technique could be extended to other planets that orbit cooler stars in the so-called "Goldilocks Zone," where the temperature is not too hot, not too cold but just right for nurturing life.

"This is a crucial stepping stone to eventually characterizing pre-biotic molecules on planets where life could exists," said JPL's Mark Swain, who led the investigation.

"This observation is proof that spectroscopy can eventually be done on a cooler and potentially habitable Earth-sized planet orbiting a dimmer red dwarf-type star."

More than 270 planets beyond our solar system, known as exoplanets, have been spotted since the first one was detected 13 years ago.

Although the tally of planets is steadily rising, the big frustration has been to garner details about their chemical composition -- the key to identifying whether any holds the potential for life.

Swain's team used the powerful NICMOS spectroscopy camera aboard the Hubble to get snapshots as HD 189733b passed on a direct line between its own star and Earth on a day in May last year.

The light from the star passed through the planet's atmosphere, bringing with it telltale chemical signatures -- but the chief task lay in finding these needles in a haystack of wavelengths.

The observations also confirmed the existence of water molecules, something that had been inferred earlier by NASA's Spitzer space telescope.

In a commentary, University of Arizona planetary scientist Adam Showman said that the achievement was a remarkable step forward in exoplanet knowledge.

The Hubble and Spitzer telescopes are now entering old age, but new-generation, more powerful orbital platforms are under development, he noted.

"We are thus now seeing but the opening salvo in a revolution that will extend humankind's view of planetary worlds far beyond the provincial boundaries of our solar system," said Showman, writing in Nature.

Related Links:

Irene Klotz's blog: Space Diary

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How Stuff Works: Planet Hunting