Carbon Dioxide Detected on Exoplanet

This story was originally posted back in late November, but in reading through the updated piece at Science News, I was struck by the last line. First, the main story.

Essentially, carbon dioxide has been detected in the atmosphere of a Jupiter-sized planet orbiting the star HD 189733 (am I the only one who thinks these stars should be given really great proper names when you find something like this?). This planet has already given up the information that it has water vapour and carbon monoxide in its atmosphere, and is now the first exoplanet of any size on which carbon dioxide has been detected.

"One explanation for the carbon dioxide, says Swain [Mark Swain of NASA's JPL], is that because the planet lies so close to HD 189733, completing an orbit in just 2.2 days, it receives an unusually high dose of ultraviolet light from the star. The intense ultraviolet radiation could have altered the chemical composition of the planet’s atmosphere, breaking down compounds and creating new ones. If other explanations can be ruled out, “this would be the first real evidence that [ultraviolet starlight] can make a substantial contribution to the atmosphere of these extrasolar planets,” Swain says. In the solar system, for example, ultraviolet light from the sun is believed to have triggered complex chemical reactions in Earth’s early atmosphere."

-- Science News, 9 December 2008

But the bit that I found particularly interesting was the last paragraph:

"The new finding “means that three of the Big Four biomarkers for habitable/inhabited worlds have now been seen: water, methane and now carbon dioxide,” Boss [Alan Boss of the Carnegie Institute for Science] says. “The only one that has not yet been detected is oxygen/ozone.”

Ibid

That last sentence is incredibly exciting. It means that astronomers are rapidly closing in finding out whether or not there are other Earth-like worlds out there, and that the chances for such a place look quite a lot more likely than they did twenty years ago. Think about that for a moment: what do you think the implication of finding another planet like Earth would be? Answers in the comments, if you're so inclined.