Researchers at Nasa's Jet Propulsion Laboratory report that the Hubble Space Telescope has found CO2 on a planet outside our solar system. HD 189733b is unlikely to actually harbor extraterrestrial life, being a Jovian class planet with a surface temperature of 1,292 degrees F. But the successful detection bodes well for our search for extraterrestrial life.

Although Hubble was originally designed to observe distant stars and galaxies, researcher Mark Swain discovered that he could use its infrared imaging and multi-object spectrometer to identify gases. Using what is called the "secondary eclipse method," Swain waits for the target planet to be eclipsed by its parent star, and compares the light spectra before and after the eclipse. Swain can then subtract the known spectra of the star, and deduce the atmospheric content of the target planet.

The finding is considered proof of concept for the continued search for extraterrestrial life, using the indirect method ("don't look for the camel, look for the fleas"). This way of thinking looks for the byproducts of life, as well as the materials (including CO2) which we believe to be critical to sustaining life. This is different from, although complementary to, direct methods such as SETI's search for alien broadcast signals.

Although the news is a feather in the Hubble Telescope's cap, its use for the secondary eclipse method will soon be, well, eclipsed. When the James Webb Space Telescope is launched in 2013, NASA reports that it will be able to make more precise measurements of spectra, which will improve the comparison data.