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A comprehensive survey of 10 Jupiter-sized exoplanets by Spitzer Space telescopes and NASA's Hubble has helped the team of researchers to solve a very old mystery, why there is less water present in some of these planets than expected. The results of the survey explain a lot about the range of planetary atmospheres in our galaxy and the way planets assemble. Out of the 2,000 planets that orbit the other stars confirmedly, a subcategory of those are similar to Jupiter in characteristics and are gaseous in nature. However, they orbit very close to their stars, that makes them very hot. Since they are so close to the star, it becomes difficult to observe these planets in the starlight glare. Because of this difficulty, Hubble could only explore a few Jupiters in the past. According to these studies, several planets were found to hold much less water than was projected by atmospheric models, said Science 2.0.

The problem was solved by a team of astronomers by making a comprehensive spectroscopic catalogue of the atmospheres of exoplanet. The orbit followed by the planets in the catalogue is such that it passes in front of the parent star, as is visible from the Earth. In between this transit, the starlight emanating from it passes through the outer atmosphere of the planet. "The atmosphere leaves its unique fingerprint on the starlight, which we can study when the light reaches us," explains co-author Hannah Wakeford, now at NASA's Goddard Space Flight Center in Greenbelt, Maryland, reported Science News Line

"I'm really excited to finally see the data from this wide group of planets together, as this is the first time we've had sufficient wavelength coverage to compare multiple features from one planet to another," says David Sing of the University of Exeter, U.K., lead author of the paper. "We found the planetary atmospheres to be much more diverse than we expected."

"Our results suggest it's simply clouds hiding the water from prying eyes, and therefore rule out dry hot Jupiters," explained co-author Jonathan Fortney of the University of California, Santa Cruz. "The alternative theory to this is that planets form in an environment deprived of water, but this would require us to completely rethink our current theories of how planets are born," as per Jet Propulsion Laboratory, NASA.