"These molecules serve as a probe," he said. "Measuring what molecules are present and how much is present, we can start to learn more about the conditions, composition and chemistry going on in the exoplanet's atmosphere."
Swain said more observations are planned to verify his findings. But Sara Seager, an exoplanet researcher at the Massachusetts Institute of Technology who was not part of Swain's study, said she was "cautiously optimistic" the observation will hold up.
"The Hubble Space Telescope was never designed to make measurements like this. They are really pushing the telescope to its limit," she said.
The observations required an extraordinary degree of stability. It was a stretch for Hubble and not yet possible with ground-based observatories.
"It's just amazing," Seager said. "The big breakthrough is being able to detect any molecule in the atmosphere."
As astronomers begin to look at other exoplanets for methane, they can't be sure, even if they find it, that its discovery by itself would indicate life. "We may never be able to attribute methane 100 percent to life," Seager said.
But if they find abundant methane around a smaller, cooler and more Earth-like planet, she said, "we may be able to think it might come from life. Processes that are not biological tend to produce much smaller amounts of methane."
The strongest sign of life would be evidence of both abundant methane and abundant oxygen - two molecules that, without life to constantly replenish them, would combine to form something else and disappear.
"We have a good chance of doing this, if we're lucky, with the James Webb Space Telescope," Seager said. Webb is planned for launch in 2013. Its science program will be managed by the Space Telescope Science Institute in Baltimore.
frank.roylance@baltsun.com
