For more than 100 years, scientists have struggled to find signs of life elsewhere in the universe apart from our blue planet. This time NASA has managed to trace signs of water in the atmosphere of five alien worlds.

On Tuesday, the space agency announced that with the assistance of the powerful Hubble Space Telescope, scientists have succeeded in tracing faint signatures of water in the atmospheres of five planets outside our own Milky Way. Though the presence of water on exoplanets has been reported earlier, this is the first study that conclusively measures and evaluates the profiles as well as intensities of the signature of water on the multiple alien planets.

The scientists noticed that the strength of water on the multiple planets that orbit nearby stars varied to some extent. The multiple worlds are WASP-17b, HD209458b, WASP-12b, WASP-19b and XO-1b. Traces of water on these multiple worlds were detected by Hubble's high performance Wide Field Camera 3 that has the potential to peer into the hazy atmosphere of exoplanets that are located trillions of miles away from Earth. Among the five alien worlds, the strongest signs of water were seen in WASP-17b that has a puffed up atmosphere and also HD20948b.

"We're very confident that we see a water signature for multiple planets," Avi Mandell, a planetary scientist at NASA's Goddard Space Flight Center in Greenbelt, Md, said in a statement. "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."

The five alien worlds detected were a part of a census of exoplanets atmosphere that was led by L. Drake Deming of the University of Maryland in College Park.

Using the space telescope's Wide Field Camera 3, the scientists analyzed the absorption of light through their atmospheres. They made the observations in the range of infrared wavelengths, where if water traces are present, they would appear and easily be detected. On finding water, the scientists then compared the shapes and intensities of the absorption profiles. The confirmation of water in the atmosphere of the alien worlds came from the consistency of the water signature.

According to Deming, it is extremely challenging to detect an exoplanet, but in this case with the help of Hubble they detected water signals on the planets. Though the traces of water were very slight, the team believes that it was due to the deposit of dust and haze that blankets the atmosphere.

The five massive worlds that orbit at close proximity to their host stars are in fact hot Jupiters. The scientists were baffled to notice that all the five alien worlds were hazy.

"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," said Heather Knutson of the California Institute of Technology, a co-author on Deming's paper. "This suggests that cloudy or hazy atmospheres may in fact be rather common for hot Jupiters."

These interesting finds can be made only when the planets pass in front of their stars because at that time the scientists can easily identify the gases in the atmosphere of the alien world by determining the wavelength of the light that is transmitted.

The findings were reported in the Astrophysical Journal paper.