Methane and water discovered on extrasolar planet

Astronomers have discovered methane in the atmosphere of planet HD 189733b which is 63 light years away. This is the first time that an organic molecule has been detected on a planet outside our Solar System. Water has also been discovered but the planet is far too hot to support life.

The discovery, unveiled in the journal Nature, is an important step towards exploring new worlds that might be more hospitable to life. Under certain circumstances, methane can play a key role in prebiotic chemistry. Co-author Giovanna Tinetti from University College, London, said "This planet is a gas giant very similar to our own Jupiter, but orbiting very close to its star. The methane here, although we can call it an organic constituent, is not produced by life - it is way too hot there for life."

Dr Tinetti, and co-authors Mark Swain and Gautam Vasisht, from NASA’s Jet Propulsion Laboratory in Pasadena, California, found the tell-tale signature of methane in the planet's atmosphere using the Hubble Space Telescope. The observations were made as the planet passed in front of its parent star, as viewed from Earth. As the star's light passed briefly through the planet's atmosphere, the gases imprinted their chemical signatures on the transmitted light Spectroscopy revealed the chemical "fingerprint" of methane.

It shows that Hubble, Spitzer and a new generation of space telescopes yet to be launched can detect organic molecules on other extrasolar planets using spectroscopy, they say. Dr Swain said: "This is a crucial stepping stone to eventually characterising prebiotic molecules on planets where life could exist." Dr Tinetti said the technique could eventually be applied to extrasolar planets that appear more suitable for life than HD 189733b. "I definitely think that life is out there. My personal view is it is way too arrogant to think that we are the only ones living in the Universe." She said

Adam Showman of the Department of Planetary Sciences at the University of Arizona, US, said scientists were finally starting to move beyond simply discovering extrasolar planets to truly characterising them as worlds. Dr Showman, who was not part of the study, said: "The discovery does not by itself have any direct implications for life except that it proves a technique which might potentially be useful for characterising the atmosphere of rocky planets when we finally start discovering them."