Large rocky exoplanet ‘could have right conditions to sustain alien life’ 

Large rocky planet 124 light years away from Earth appears to be covered in WATER and ‘could have right conditions to sustain alien life’

The planet is about twice the size of the Earth with possible lakes and vast seasResearchers predict they will know whether it has signs of life within the decade Large amounts of water vapour have been discovered encircling the planetIt has been called K2-18b by astronomers who plan to study it in more detail when the James Webb Space Telescope comes online

A large rocky planet twice the size of the Earth has been discovered orbiting inside its star’s habitable zone and could have the right conditions to sustain alien life.

The exoplanet, called K2-18b, is 124 light years away appears to be covered in water, according to researchers from Cambridge University.

While they can’t tell whether there is life on the planet now, by the end of the decade scientists think new telescopes will be able to spot the gases made by alien species.

Computer models suggest an ocean world – with liquid water below the atmosphere at pressures and temperatures similar to those found in our seas.

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Artist’s impression of K2-18b with its potentially vast oceans and lakes across the ‘waterworld’ planet – it may contain signs of life

Last autumn two different teams of astronomers detected water vapour encircling the exoplanet and new analysis hints at a life supporting ecosystem.

The Cambridge team confirmed the atmosphere is hydrogen-rich with a significant amount of water vapour but levels of other chemicals such as methane and ammonia were lower than expected.

The next generation of space telescopes being launched this decade will be able to investigate if this is down to biological processes.

If the lower levels of methane and ammonia are due to biological processes then it is likely that planet contains active life of one form or another. 

Lead author Dr Nikku Madhusudhan said water vapour has been detected in the atmosphere of a number of exoplanets studied so far.

‘Even if the planet is in the habitable zone, that doesn’t necessarily mean there are habitable conditions on the surface,’ Madhusudhan said.

‘To establish the prospects for habitability, it’s important to obtain a unified understanding of the interior and atmospheric conditions on the planet – in particular, whether liquid water can exist beneath the atmosphere.’

The researchers determined the composition and structure of both the atmosphere and interior for the first time using existing observations.

They used detailed numerical and statistical models and took into account its radius and mass. These are 2.6 and 8.6 times greater than Earth’s, respectively.

K2-18b is in a planet category known as a ‘super Earth’ – and has a temperature cool enough to have liquid water, between 32F and 104F – similar to Earth.

Given its size it’s been suggested it’s more like a small Neptune than a large Earth.

This is likely to cause it to have a significant hydrogen ‘envelope’ surrounding a layer of high-pressure water – with an inner core of rock and iron.

If the hydrogen envelope is too thick, the temperature and pressure at the surface of the water layer beneath would be far too great to support life.

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