Spitzer Continues To Amaze Researchers

For the first time ever, a NASA telescope has captured enough light from planets outside Earth's solar system to identify individual molecules present in their atmospheres. The space agency says data obtained by the Spitzer Space Telescope is a significant step toward being able to detect possible life on rocky exoplanets, and comes years before astronomers had anticipated.

"This is an amazing surprise," said Spitzer project scientist Dr. Michael Werner of NASA's Jet Propulsion Laboratory, Pasadena, CA. "We had no idea when we designed Spitzer that it would make such a dramatic step in characterizing exoplanets."

Spitzer, a space-based infrared telescope, obtained the detailed data, called spectra, for two different gas exoplanets. Called HD 209458b and HD 189733b, these so-called "hot Jupiters" are, like Jupiter, made of gas, but orbit much closer to their suns.

The data indicate the two planets are drier and cloudier than predicted. Theorists thought hot Jupiters would have lots of water in their atmospheres, but surprisingly none was found around HD 209458b and HD 189733b.

According to astronomers, water might still be present -- but buried under a thick blanket of high, waterless clouds that may be filled with dust.

One of the planets, HD 209458b, showed hints of tiny sand grains, called silicates, in its atmosphere. (Need a visual? Think Phoenix, AZ during a summertime wind storm -- times 100... Ed.) NASA theorizes this could mean the planet's skies are filled with high, dusty clouds unlike anything seen around planets in our own solar system.

"The theorists' heads were spinning when they saw the data," said Dr. Jeremy Richardson of NASA's Goddard Space Flight Center in Greenbelt, MD.

"It is virtually impossible for water, in the form of vapor, to be absent from the planet, so it must be hidden, probably by the dusty cloud layer we detected in our spectrum," he said.

A spectrum is created when an instrument called a spectrograph splits light from an object into its different wavelengths, just as a prism turns sunlight into a rainbow. The resulting pattern of light, the spectrum, reveals "fingerprints" of chemicals making up the object.

Until now, the only planets for which spectra were available belonged in our own solar system. The planets in the Spitzer studies orbit stars that are so far away, they are too faint to be seen with the naked eye. HD 189733b is 370 trillion miles away in the constellation Vulpecula, and HD 209458b is 904 trillion miles away in the constellation Pegasus. That means both planets are at least about a million times farther away from us than Jupiter.

In the future, astronomers hope to have spectra for smaller, rocky planets beyond our solar system. This would allow them to look for the footprints of life -- molecules key to the existence of life, such as oxygen and possibly even chlorophyll.

"With these new observations, we are refining the tools that we will one day need to find life elsewhere if it exists," said Dr. Mark R. Swain of JPL. "It's sort of like a dress rehearsal."

Previous observations of HD 209458b by NASA's Hubble Space Telescope revealed individual elements, such as sodium, oxygen, carbon and hydrogen, that bounce around the very top of the planet, a region higher up than that probed in the Spitzer studies and a region where molecules like water would break apart.

FMI: www.nasa.gov/spitzer, www.spitzer.caltech.edu