Missing water mystery of exoplanets solved

London: Astronomers have studied the atmospheres of ten hot, Jupiter-sized exoplanets in detail and solved a long-standing mystery - why some of these worlds seem to have less water than expected.

Researchers used multiple observations from both the NASA/ESA Hubble Space Telescope and NASA's Spitzer Space Telescope to study the planets, which are of various masses, sizes, and temperatures, across an unprecedented range of wavelengths.

All of the planets have a favourable orbit that brings them between their parent star and Earth. As the exoplanet passes in front of its host star, as seen from Earth, some of this starlight travels through the planet's outer atmosphere.

"The atmosphere leaves its unique fingerprint on the starlight, which we can study when the light reaches us," said Hannah Wakeford, from the NASA Goddard Space Flight Centre.

These fingerprints allowed the team to extract the signatures from various elements and molecules - including water - and to distinguish between cloudy and cloud-free exoplanets, a property that could explain the missing water mystery.

The researcher's models showed that, while apparently cloud-free exoplanets showed strong signs of water, the atmospheres of those hot Jupiters with faint water signals also contained clouds and haze - both of which are known to hide water from view.