Water discovered for first time in atmosphere of habitable exoplanet

Water found for first time on potentially habitable planet with Earth-like warmth that could sustain life as we know it, scientists reported Wednesday.

8-times the mass of Earth & twice as massive, K2-18b orbits in its star’s “habitable zone” at a distance-neither too far nor too close where water can survive in liquid form, they reported in the journal Nature Astronomy.

“This planet is the best solicitor we have outside the solar system.” 

in the search for clues of life, co-author Giovanna Tinetti, an astronomer at University College London, told AFP.

“We cannot believe that it has oceans on the surface, but it is a real possibility.” 

Of the more than 4,000 exoplanets discovered to date, this is the first known to combine a rocky surface and an environment with water.

Most exoplanets with atmospheres are enormous balls of gas & some of the rocky planets for which data is possible to seem to have no atmosphere at all.

Even if they did, most Earth-like planetoids are too distant from their stars to have liquid-water or so close that any H2O has vanished.

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Discovered in 2015, K2–18b is one of the hundreds of so-called “super-Earths” — planets with less than 10- times the mass of ours — found by NASA’s Kepler spacecraft. 

Future space missions are required to detect hundreds more in the coming decades.

Is Earth unique?’ –

“Finding water in a possibly comfortable world other than Earth is especially exciting,” stated lead-author Angelos Tsiaras, also from UCL.

“K2 — 18b is not ‘Earth 2.0’,” he said. “However, it takes us closer to solving the fundamental question: is the Earth unique?”

Working with spectroscopic data taken in 2016 & 2017 by the Hubble Space Telescope, Tsiaras & his team used open-source algorithms to analyse the starlight penetrated through K2-18b’s atmosphere. 

Water found for first time on potentially habitable planet They found the clear signature of water vapour. Exactly how much remains unknown, but computer modelling suggested frequencies between 0.1 and 50 per cent. 

By contrast, the percentage of water vapour in Earth’s environment varies between 0.2 per cent above the poles and up to four per cent in the tropics.

There was also proof of hydrogen & helium as well. Nitrogen & methane may also be started but with modern technology remain undetectable, the study said.

Further study will be able to discover the extent of cloud coverage and the percentage of water in the atmosphere.

First of many

Water is essential in the search for life, in part because it provides oxygen.

“Life, as we know, is based on water,” stated Tinetti. 

K2-18b orbits a red dwarf-star about 110 light-years distant — a million billion km — in the Leo stars of the Milky Way and is seemingly attacked by more harmful radiation than Earth.

“This likely is the 1st of many discoveries of possibly inhabitable planets,” said UCL scientist Ingo Waldmann, also a co-author. 

“This is not only because super Earths like K2-18b are the most popular planets in our galaxy, 

but also because red dwarfs — stars less than our Sun — are the most common stars.”

The new generation of space-based star gazing tools led by the James Webb Space-Telescope and the European Space Agency’s ARIEL -mission will be able to identify exoplanet atmospheres in far more comprehensive detail. 

ARIEL, slated for a 2028 launch, will cover some 1,000 planets, a significant enough sampling to look for models and recognise outliers.

“Over 4,000 exoplanets have been identified, but we don’t know much about their work and nature,” said Tinetti.

“By following a large sample of planets, we hope to reveal secrets about their chemistry, formation and evolution.”


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