14 DAY TRIAL // Astronomers have just made the first attempts of looking for water in planets outside the Sun system, but the first results let them down.
The two distant, hot gaseous planets they have targeted were supposed to have harbored water in their atmospheres as the two suns orbited by those are rich in hydrogen and oxygen, the atoms water is made of.
But when two astronomer teams investigated the planets' atmospheres employing light spectra to assess their chemical composition, they found no water. One planet was found to have an atmosphere rich in fine silicate-particle clouds, while form the other any chemical researcher looked for was missing.
Both teams used NASA's Spitzer Space Telescope. "We had expected this tremendous signature of water ... and it wasn't there," said the study leader of one team, Carl Grillmair of the California Institute of Technology and Spitzer Science Center. "The very fact that we've been surprised here is a wake-up call. We obviously need to do some more work."
"These surprising "sniffs of air from an alien world" tell astronomers not to be so Earth-centric in thinking about other planets", said David Charbonneau, a Harvard astronomy professor. "These are very different beasts. These are unlike any other planets in the solar system. We're limited by our imagination in thinking about the different avenues that these atmospheres take place in", he added. "Our own solar system has two planets without water in the atmosphere: Mercury, which doesn't have an atmosphere, and Venus, which is a different type of planet from the huge gaseous ones that would be expected to have the components of water in the air", explained Grillmair.
There are 213 known extrasolar planets, but only 14 of them are approachable with the current technique, and only 8 of them are close enough to be visible. Grillmair's team investigated HD 189733b, the closest, situated at 360 trillion miles from the Earth in the constellation Vulpecula ("Little fox").
The silicate rich planet, HD209458b (photo), is located at a distance of 900 trillion miles from Earth in the constellation Pegasus.
Astronomers do not give up: they suggest that water could be hiding under dust clouds, or the airborne water has temperatures similar to silicates, turning it impossible to be detected by infrared spectrograph. "The other finding on the more distant of the two planets seems to indicate that the atmosphere is full of silicon-oxygen compounds," said study lead author L. Jeremy Richardson of NASA's Goddard Space Flight Center.
"They'd be like dust grains and they would form clouds. And that cloud of silicates could be blocking the space telescope from measuring lower-lying water," he said.
Image credit: NASA