This is just another of the 270+ planets found so far outside our solar system. Although, as the article from Wired Magazine mentions, it's probably too big of a planet for any form of life like we find on Earth, the chemical composition strongly suggests signs of life. In fact, scientists know of no other way such chemicals could arise naturally, without the help of living things. More evidence we are not alone…jg

Molecular Basis of Life Discovered on Extrasolar Planet

By Alexis Madrigal 03.19.08 | 6:15 PM

NASA released this rendering of HD 189733b, an extrasolar planet more than 60 light years from Earth, which has the organic molecule methane in its atmosphere.
Courtesy NASA, ESA, and G. Bacon (STScI)

Scientists using the Hubble Space Telescope have for the first time found the telltale signature of methane, an organic molecule, in the atmosphere of a planet outside our solar system.

Methane is one of the chemicals of life, an organic compound in the class of molecules containing carbon. However, no life is likely to exist on the large, gaseous planet known as HD 189733b. Its daily temperatures can reach 1,340 degrees Fahrenheit.

"These measurements are a dress rehearsal for future searches for life," said Mark Swain, a scientist at NASA's Jet Propulsion Laboratory and the lead author of a new study that appears in Nature tomorrow. "If we were able to detect [methane] on a more hospitable planet in the future, it would really be something exciting."

The latest atmospheric observation is a clear step toward understanding planets across the galaxy. Since the discovery of the first so-called exoplanet 13 years ago, scientists have been able to glean little about the 270-plus known extrasolar planets. Even rough sizes and masses have been calculated for a mere 30 of those planets. It is only in the last year that scientists have begun to characterize the conditions on these planets, like their surface temperatures, and as in this case, the chemical composition of their atmosphere. Such findings not only shed light on other solar systems, but also on our own.

"The work ties these extrasolar planets to our own [solar system's] planets. We can start to understand these giant planets as a class of astronomical objects," said Jonathan Fortney, an astronomy professor at the University of California, Santa Cruz. "You can start to say now that the Jupiter-like planets in other solar systems seem to be similar to our own Jupiter."

HD 189733b, a so-called "hot Jupiter," located 63 light years away, has proven a boon for scientists studying exoplanets. Its large size and proximity to its star mean that it dims the star's light more than any other known exoplanet. Combine that with its home star's high brightness, and scientists find that the system creates the best viewing conditions of any known extrasolar system.

"Its orbit is such that it's just aligned with Earth, so you see as the planet comes in front of the star and it obscures a bit of the light," said Gilda Ballester, a planetary scientist at the University of Arizona.

At different wavelengths, every atom and molecule has its own telltale footprint, so scientists can convert what are known as absorption spectra into the chemical composition of the object they're looking at.

The technique, known as spectrography, will remain the main scientific technique for learning about exoplanets into the future, Fortney said, with planets that could support life.

"These techniques are going to be the same techniques we're using for even smaller exosolar planets, for example terrestrial or Earth-like planets," said Seth Redfield, a Hubble postdoctoral fellow at the University of Texas at Austin, who previously identified sodium in HD 189733b's atmosphere.

Redfield noted that merely studying exoplanets many times the size of Earth was pushing the envelope of current science.

"Twenty years from now, we'll be able to do this for superearths," Fortney said. "We'll be able to see methane in the atmosphere of an Earth-like planet."

To do so, however, astronomers will need new tools. Swain's team used Hubble's Near Infrared Camera and Multi-Object Spectrometer to capture rough spectrographic data. They were forced to use the low-resolution tool because the dedicated instrument for spectrography -- the Space Telescope Imaging Spectrograph -- broke in 2003, Redfield said.

"The STIS spectrograph would get resolutions several orders of magnitude higher than the tool they used," Redfield said.

He said NASA was planning to try to fix the tool in late summer of this year, and that access to the tool could lead to new discoveries. In the meantime, scientists will keep plugging away, revealing the properties of planets dozens of light years away, molecule by molecule.

"We know so little observationally about these planetary atmospheres that any sort of measurement is tremendously exciting," Redfield said.