Large Planet Discovered That Could Harbour Life

Written by The Daily Mail on September 18, 2023. Posted in Current News

Scientists have made an exciting and potentially ground-breaking discovery in the search for alien life, after detecting signs of a gas produced only by living organisms on a distant water planet

K2-18 b, which is more than eight times the size of Earth and 120 light-years away from us, sits within the habitable zone of its cool dwarf star in the Leo constellation.

It is thought to be a ‘Hycean’ world — a relatively new class of exoplanet possessing key ingredients for alien species because of their hydrogen-rich atmospheres and oceans of water.

But it is the presence of something else that has got astronomers even more excited.

A gas ‘uniquely associated with life’ when found on Earth has been discovered in the atmosphere of K2-18 b, which is known as a ‘super Earth’ because it is bigger than our planet but smaller than Neptune.

The compound dimethyl sulphide (DMS) – a complex molecule made up of carbon, hydrogen and sulphur atoms – was detected alongside two carbon-carrying gases, leaving researchers feeling a ‘a mix of shock and excitement and disbelief’.

‘On Earth, this is only produced by life,’ NASA said.

‘The bulk of the DMS in Earth’s atmosphere is emitted from phytoplankton in marine environments.’

Despite the excitement, scientists have stressed that more observations by the James Webb Space Telescope will be needed to confirm the presence of DMS.

If the discovery is validated it would make K2-18b among the most likely worlds where alien life could exist, alongside the likes of Mars and the icy moons of Jupiter and Saturn in our own solar system.

The super Earth was also found to have large amounts of carbon dioxide and methane in its atmosphere, the presence of which could suggest it is habitable or possibly even inhabited already.

This certainly points to K2-18b being a ‘Hycean’ world, but because both gases can be produced by inorganic process they don’t offer proof of alien life on their own.

Lead author of the research, Nikku Madhusudhan, said even the prospect of DMS existing on a faraway exoplanet was ‘mind-boggling’.

‘Our discovery is a major development in exoplanetary science, particularly the demonstration that we can detect carbon-based molecules in low-mass exoplanets in the habitable-zone,’ the University of Cambridge professor told MailOnline.

‘The further inference of the possibility of an ocean in this planet is another major advancement.

‘When we first saw the data it was a very exciting and surreal experience to be making such a fundamental discovery.’

Professor Madhusudhan added: ‘Traditionally, the search for life on exoplanets has focused primarily on smaller rocky planets, but the larger Hycean worlds are significantly more conducive to atmospheric observations.

‘Upcoming Webb observations should be able to confirm if DMS is indeed present in the atmosphere of K2-18 b at significant levels.’

NASA’s $10 billion (£7.4 billion) observatory is able to analyse the chemical make-up of a distant planet by capturing the light from its host star after it has passed through the planet’s atmosphere on its way to Earth.

Gases in the atmosphere absorb some of the starlight but each leave tell-tale signatures in the spectrum of light that astronomers can then unpick.

As well as being known as a super Earth, K2-18b is also classified as a ‘sub-Neptune’ planet.

These worlds are not found in our solar system but are defined as any planet that has a smaller radius than the ice giant that is furthest from our sun.

Sub-Neptunes are poorly understood because of their distance from us, so the nature of their atmospheres is a matter of debate among astronomers.

‘Although this kind of planet does not exist in our solar system, sub-Neptunes are the most common type of planet known so far in the galaxy,’ said researcher Subhajit Sarkar of Cardiff University.

‘We have obtained the most detailed spectrum of a habitable-zone sub-Neptune to date, and this allowed us to work out the molecules that exist in its atmosphere.’

K2-18b’s large size – with a radius 2.6 times the radius of Earth – means that the planet’s interior likely contains a large mantle of high-pressure ice, like Neptune, but with a thinner hydrogen-rich atmosphere and an ocean surface.

Although Hycean worlds are predicted to be covered in water, researchers say it is also possible that the ocean is too hot to be habitable or be liquid.

Since the first exoplanet was discovered in 1992, over 5000 have been spotted outside of our solar system.

The majority are planets between the sizes of Earth and Neptune, often referred to as super Earths, mini-Neptunes or sub-Neptunes.

They can be predominantly rocky or ice giants with hydrogen-rich atmospheres, or something in between.

Earlier studies of such planets found that the pressure and temperature beneath their hydrogen-rich atmospheres would be too high to support life.

But in 2021, research found that in certain conditions the worlds could support life.

Alongside confirming whether DMS is present on K2-18b, researchers will now look for other biomarkers such as methyl chloride that are uniquely created by life.

If they are, it would generate great excitement and thrust the world to the front of the queue in the hunt for alien species.

See more here dailymail.co.uk

Editor’s note: it should be remembered that 97 percent of the CO2 in our atmosphere comes from natural processes, and the same will probably be true of K2-18b.

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