Scientists Have Discovered Water On A Potentially Habitable World

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Water vapour has been detected on a potentially habitable super-earth known as K2-18b, located about 110 light years away.

Water vapor has turned up on planets outside our solar system before, but none of those were anything close to liveable. More important: It sits in its star's "habitable zone", where it is bathed in the right amount of warmth to allow for liquid water on its surface.

K2-18b is one of hundreds of "super-Earths" - exoplanets with masses between those of Earth and Neptune - found by Kepler. This is now the only known exoplanet that contains water and also temperatures that are within the range necessary for supporting life, making it a key discovery for future potential missions.

Using the Hubble Space Telescope, a team from University College London performed a spectrographic survey of K2-18b's atmosphere, resulting in the detection of a distinctive water signature. K2-18b is said to have about the same density as Mars, suggesting that it is a rocky planet. NASA's TESS mission is expected to detect hundreds more super-Earths in the coming years. "While not a true Earth-analogue due to its size, this bodes well for our exploration of small planets", Josh Lothringer, who studies exoplanet atmospheres at Johns Hopkins University in the U.S., said on Twitter.

Both teams found that water vapor is nearly certainly present in the atmosphere of this super-Earth. All five planets appear to have a high-altitude haze that weakens water's signal from deeper within their atmospheres. The red dwarf K2-18 is roughly 111 light-years from Earth and is ~2.7 percent as luminous as our own sun.

While the study we've been discussing has not yet been peer-reviewed, Nature Astronomy has published the results of a different second study, which also confirms the presence of water vapor in K2-18b's atmosphere. Even a planet like K2-18b can be examined only with humanity's most sensitive space telescope - the Hubble.

The finding makes the world - which is called K2-18b - a plausible candidate in the search for alien life.

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Further studies are required to estimate cloud coverage and the percentage of atmospheric water present, the researchers said. However, it brings us closer to answering the fundamental question: "Is the Earth unique?", Tsiaras said.

Given the high level of activity of its red dwarf star, K2-18b may be more hostile to life as we know it than Earth, as it is likely to be exposed to more high-energy radiation.

In addition to water, Hubble also detected traces of hydrogen, an observation that intrigued Tom Louden, a physicist at the University of Warwick and an expert on exoplanetary atmospheres.

Though humans are unlikely to ever set foot on the remote world with current technologies, astronomer Jonti Horner of the University of Southern Queensland told ABC the discovery would help researchers understand other Earth-like planets going forward.

Benneke stated that although water exists in liquid water clouds on K2-18 b, the rain falls through thick gas before it hits the surface, heating it so it becomes gas before it reaches the planet's surface.

So the only option is to wait for the next generation of space telescopes to be launched in the 2020s and to look for gasses in the planet's atmosphere that could only be produced by living organisms, the report in BBC News had stated quoting UCL's Dr Ingo Waldmann.

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