- EXPLORE FURTHER: Enigmatic Martian formations 'suggest life existed on the Red Planet'
An ocean-filled planet far away, brimming with living creatures.
This could be the most plausible explanation following a recent finding by researchers who claim to have identified the strongest indications so far of extraterrestrial life. solar system .
Using data from the James Webb The James Webb Space Telescope (JWST), with astronomers, guided by the University of Cambridge , has found large amounts of chemicals produced exclusively by living organisms on our planet.
They have detected the chemical signatures of dimethyl sulfide (DMS) and dimethyl disulfide (DMDS), which are compounds mainly generated by microbial organisms like marine phytoplankton.
These have been found in the atmosphere of exoplanet K2-18b, situated approximately 124 light-years away from Earth in the constellation Leo.
This represents the 'most potent indication so far' of life beyond our solar system, according to specialists who view this as a 'significant, transformative event.'
The planet revolves around a red dwarf star within the so-called 'habitable zone,' which is deemed the most promising area for discovering life-sustaining worlds.
K2-18b has a diameter 2.6 times greater and a mass 8.6 times more than Earth’s, and specialists think it is probably enveloped by an ocean, categorizing it as a so-called 'Hycean planet.'
The planet has a climate akin to Earth's, yet it orbits extremely near to its star, resulting in a year that spans only 33 days.
Previous findings detected methane and carbon dioxide in its atmosphere — marking the first instance where carbon-based compounds were found on an exoplanet located within the habitable zone.
Currently, an examination of fresh data has revealed compounds that, according to what scientists know, are exclusively generated by living organisms.
The levels of DMS and DMDS in K2-18b's atmosphere vary significantly from those on Earth, where they typically fall below one part per billion by volume.
On K2-18b, they are believed to be thousands of times more powerful — exceeding 10 parts per million.
Professor Nikku Madhusudhan, who hails from the Institute of Astronomy at Cambridge, headed the study.
He stated, 'Previous theoretical studies suggested that significant amounts of sulfur-containing gases such as DMS and DMDS could be present in Hycean environments.'
'Now that we have witnessed it, as was anticipated.'
'Taking into account all our knowledge of this planet, the idea of a Hycean world where oceans brim with life aligns most closely with the information we possess.'
He mentioned that although the findings are thrilling, it's crucial to gather additional information prior to asserting that life exists on another planet.
Even though he remains guardedly hopeful, unidentified chemical reactions occurring on K2-18b might explain these observations.
Additional observations from the JWST are required to ensure their findings aren't merely due to random variation.
His team are also hoping to conduct further experiments to determine whether DMS and DMDS can be produced non-biologically at the level currently detected.
'In decades ahead, we might reflect upon this moment as the turning point when the living universe became accessible,' stated Professor Madhusudhan.
'This could be the tipping point, where suddenly the fundamental question of whether we're alone in the universe is one we're capable of answering.'
To determine the chemical composition of the atmospheres of faraway planets, astronomers analyse the light from its parent star as the planet transits, or passes in front of the star.
As K2-18b transits, JWST can detect a drop in stellar brightness, and a tiny fraction of starlight passes through the planet's atmosphere before reaching Earth.
The absorption of some of the starlight in the planet's atmosphere leaves imprints in the stellar spectrum that astronomers can piece together to determine the constituent gases of the exoplanet's atmosphere.
Last year, JWST detected weak hints of 'something else happening' on K2-18b alongside the discovery of methane and carbon dioxide.
Professor Madhusudhan stated, "We weren't certain if the signal detected previously was indeed from DMS, but even the possibility encouraged us to observe again with JWST utilizing a different instrument."
Initially, the provisional hypothesis about DMS was established through observations with JWST’s NIRISS (Near-Infrared Imager and Slitless Spectrograph) and NIRSpec (Near-Infrared Spectrometer). These tools collectively span the near-infrared spectrum from 0.8 to 5 microns.
The recently conducted independent observation utilized JWST’s MIRI (Mid-Infrared Instrument) in the mid-infrared spectrum ranging from 6 to 12 microns.
"This serves as a separate body of evidence obtained through a distinct apparatus from our prior work and within a differing spectrum of light, ensuring no redundancy with earlier findings," stated Professor Madhusudhan.
'The signal came through strong and clear.'
Co-author Måns Holmberg, a researcher at the Space Telescope Science Institute in Baltimore, USA, added: 'It was an incredible realisation seeing the results emerge and remain consistent throughout the extensive independent analyses and robustness tests.'
DMS and DMDS are molecules from the same chemical family, and both are predicted to be biosignatures.
Both molecules have overlapping spectral features in the observed wavelength range, although further observations will help differentiate between the two molecules.
'Our work is the starting point for all the investigations that are now needed to confirm and understand the implications of these exciting findings,' said co-author Savvas Constantinou, also from Cambridge's Institute of Astronomy.
The team say their observations have reached the 'three-sigma' level of statistical significance – meaning there is a 0.3 per cent probability that they occurred by chance.
To reach the accepted classification for scientific discovery, the observations would have to cross the five-sigma threshold, meaning there would be below a 0.00006 per cent probability they occurred by chance.
They mentioned that approximately 16 to 24 hours of additional observing time using the JWST could assist them in achieving the crucial five-sigma significance level.
The finding was reported in the publication The Astrophysical Journal Letters.
Last month, researchers revealed the discovery of organic molecules of 'unparalleled magnitude' on Mars, providing additional proof that life might have existed there in the past.
Specialists discovered lengthy carbon chains with up to 12 linked atoms in chunks of ancient Martian rocks that are billions of years old.
These carbon-based compounds — the most extensive ones detected up until now — might stem from fatty acids, which form the foundation of lipids such as fats and oils and are produced on our planet via biological processes.
Scientists stated that this finding is of 'great interest' in the quest for possible indications of life.
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