The theory that there may be life on other planets both in our solar system and beyond seems to gain more credibility on an almost weekly basis. The latest reports from the Hubble telescope indicate that definite signs of water have been discovered on five exoplanets.

Hubble’s Wide Field Camera 3 is one of the few telescopes on Earth that are capable of distinguishing details from exoplanets, the term for planets found outside of our solar system, located many trillions of miles away. Water signatures have been identified in the atmospheres of the five planets, which are of a kind known as "hot Jupiters", massive spheres that remain in close orbit with their anchoring stars. The planets in question have the rather uninspiring titles of WASP-17b, HD209458b, WASP-12b, WASP-19b and XO-1b.WASP-17b is of particular interest to scientists, as it is described as having an "especially puffed-up atmosphere".

Water is not thought to be an uncommon feature in exoplanet atmospheres, and this is not the first time that a sniff of H2O has been detected in distant worlds, but the new study heralds a breakthrough in terms of analysis, as the scientists have been able to measure and compare profiles of the molecule in detail across multiple alien worlds. The important discovery was made by two teams of scientists, and were part of a census of exoplanet atmospheres led by L. Drake Deming of the University of Maryland in College Park.

Avi Mandell, a planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said: "We’re very confident that we see a water signature for multiple planets. This work really opens the door for comparing how much water is present in atmospheres on different kinds of exoplanets, for example hotter versus cooler ones."

Mandell’s study was published this week in The Astrophysical Journal, following Deming’s paper which was published in the same journal in September.

The powerful camera used in the studies provided information from infrared wavelengths which were analysed to detect the presence of water. Researchers were able to identify the gases in the planets’ atmospheres by assessing which wavelengths of their star’s light was transmitted and which were partially absorbed. During their orbit, exoplanets block off small amounts of light emitted by their host star, so by carefully measuring how much light is blocked off, scientists can work out the size of the planet. The composition of the planets can also affect their interaction with the light as different molecules absorb different wavelengths of light, so depending what they are made of, they will block out different parts of the light spectrum, enabling scientists to determine their structure.The process is extremely challenging, and it is only possible to collect the data if the planets are observed when they are passing in front of their stars. Consequently, fewer than 5 per cent of known exoplanets have been observed directly by astronomers.

Deming said: "To actually detect the atmosphere of an exoplanet is extraordinarily difficult. But we were able to pull out a very clear signal, and it is water."

The water signatures were not as significant as researchers had hoped, but this is thought to be because the five planets are surrounded by a cloud of dust which could affect results.

"These studies, combined with other Hubble observations, are showing us that there are a surprisingly large number of systems for which the signal of water is either attenuated or completely absent," Heather Knutson of the California Institute of Technology in Pasadena, a co-author on Deming’s paper, said in a statement. "This suggests that cloudy or hazy atmospheres may in fact be rather common for hot Jupiters."

So the potential for extra-terrestrial life to exist elsewhere in the Universe is now being tentatively confirmed by science, albeit in slow, shuffling steps. Nevertheless, this research marks a definite step forward in the search, and you can be sure that Unknown Country will bring you news of any developments on this planet, and beyond…

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