Scientists have potentially made a groundbreaking discovery 124 light-years away, detecting what could be the first signs of life on an exoplanet. However, forget images of advanced civilisations; the initial evidence points towards something far more basic – and perhaps a little slimy – hinting at microbial life thriving in the atmosphere of a distant world.
Recent findings suggest the potential for life on the exoplanet K2-18b, sparking excitement in the scientific community. This distant world, orbiting a red dwarf star, has characteristics that make it a compelling target in the search for extraterrestrial life.
In a potentially groundbreaking find, researchers employing the James Webb Space Telescope have gathered what they describe as the most compelling evidence so far for possible life outside our solar system.
Chemical Clues In K2-18 B's Atmosphere
By examining the atmosphere of an alien planet, they detected chemical signatures of gases that are only created by living organisms on Earth. The Webb telescope's observations of the planet K2-18 b revealed two gases: dimethyl sulfide (DMS) and dimethyl disulfide (DMDS).
The National Institutes of Health (NIH) states that these substances are produced by living things on Earth, mainly tiny organisms like marine phytoplankton, a type of algae.
The scientists explained that this finding hints that the planet could be full of tiny living things. However, they emphasised that they are not declaring the discovery of actual life forms. Instead, they've identified a possible biosignature—a sign of biological activity—and advise carefully interpreting the results, noting that further investigation is necessary.
Weighing The Evidence
Despite this caution, the scientists expressed enthusiasm. 'This is the strongest evidence to date for a biological activity beyond the solar system,' said astrophysicist Nikku Madhusudhan, an astrophysicist at the University of Cambridge who led the observations.
'This is a transformational moment in the search for life beyond the solar system, where we have demonstrated that it is possible to detect biosignatures in potentially habitable planets with current facilities. We have entered the era of observational astrobiology,' Madhusudhan, the main author of the research featured in the Astrophysical Journal Letters, added.
Madhusudhan pointed out that numerous projects are currently searching for evidence of life within our solar system. He mentioned various claims of environments that could support life on bodies like Mars, Venus, and several frozen moons.
Key Characteristics Of Planet K2-18 b
According to NASA, K2-18 b has a mass 8.6 times greater than Earth's, and its diameter is roughly 2.6 times that of our own planet. It circles its star within the 'habitable zone' – where liquid water, essential for life as we know it, could be on the planet's surface.
This red dwarf star, smaller and dimmer than our sun, is roughly 124 light-years away from us in the Leo constellation. A light-year represents the distance light travels in a single year, which equals 5.9 trillion miles (or 9.5 trillion kilometres). Scientists have also discovered another planet orbiting this same star.
Understanding Hycean Worlds And Their Habitability
Since the 1990s, roughly 5,800 planets orbiting stars other than our sun, known as exoplanets, have been found. Researchers have proposed the idea of hycean worlds – exoplanets with a liquid water ocean, potentially supporting microorganisms, and an atmosphere rich in hydrogen.
Previous observations made by the Webb telescope, which started its operations in 2022 after its 2021 launch, had already detected methane and carbon dioxide in the atmosphere of K2-18 b. This marked the initial discovery of carbon-based molecules in an exoplanet's atmosphere located within its star's habitable zone.
A different take from Cambridge astrophysicist Dr. Nikku Madhusudhan on the potential confirmation of the presence of large amounts of biomarker dimethyl sulfide (DMS) on exoplanet K2-18b.
— UAP Juan (@planethunter56) May 5, 2024
Yes, we are detecting a biomarker as we know it to be on earth (we obviously don't know… pic.twitter.com/opNR9HFSOe
'The only scenario that currently explains all the data obtained so far from JWST (James Webb Space Telescope), including the past and present observations, is one where K2-18 b is a hycean world teeming with life,' Madhusudhan said. 'However, we need to be open and continue exploring other scenarios.'
Madhusudhan explained that if hycean worlds do exist, 'we are talking about microbial life, possibly like what we see in the Earth's oceans.' He noted that their oceans are theorised to be warmer than our planet's.
When questioned about the possibility of more complex life forms or even intelligent beings, Madhusudhan stated, 'We won't be able to answer this question at this stage. The baseline assumption is of simple microbial life.'
Scientists Analyse Webb's Promising Findings
Scientists have long considered DMS and DMDS, which belong to the same group of chemicals, to be significant indicators of life on other planets. The Webb telescope's data suggests that one or possibly both of these gases are present in the planet's atmosphere with a 99.7% certainty. This leaves a small 0.3% possibility that the observation might be a statistical coincidence.
These gases were identified in the atmosphere at concentrations exceeding ten parts per million by volume. 'For reference, this is thousands of times higher than their concentrations in the Earth's atmosphere and cannot be explained without biological activity based on existing knowledge,' Madhusudhan said.
Scientists who were not part of the research team advised caution. 'The rich data from K2-18 b make it a tantalising world,' said Christopher Glein, principal scientist at the Space Science Division of the Southwest Research Institute in Texas.
'These latest data are a valuable contribution to our understanding. Yet, we must be very careful to test the data as thoroughly as possible. I look forward to seeing additional, independent work on the data analysis starting as soon as next week,' he added.
K2-18 b: A Sub-Neptune In The Habitable Zone
According to The Planetary Society, K2-18 b belongs to the 'sub-Neptune' category of planets. These worlds have a diameter larger than Earth's but smaller than Neptune's, which is the smallest gas planet in our solar system.
To determine the composition of an exoplanet's atmosphere, astronomers study the light from its star as the planet travels across it from Earth's viewpoint, a technique known as the transit method. Webb can observe a slight dimming of the star's light during this transit.
The James Webb Telescope and the Search for Life on K2-18b
— Black Hole (@konstructivizm) February 10, 2025
The James Webb Space Telescope is currently studying the exoplanet K2-18b, which scientists believe may harbor conditions suitable for life.
This hypothesis arises from the detection of dimethyl sulfide (DMS) in the… pic.twitter.com/XP7ZjgmcZO
A small amount of this starlight travels through the planet's atmosphere before reaching the telescope. This process allows scientists to identify the different gases present in the planet's air.
Earlier observations of this planet by the Webb telescope offered a preliminary suggestion of DMS. The latest observations employed a different instrument and examined different light wavelengths.
Are We Alone?
According to Madhusudhan, the ultimate goal in the study of planets outside our solar system is to discover proof of life on a planet similar to Earth. Madhusudhan mentioned that for thousands of years, humanity has pondered the question of whether we are alone in the cosmos.
He suggested that we might be just a few years away from potentially detecting alien life on a hycean world. However, Madhusudhan still emphasised the need for careful interpretation. 'First, we need to repeat the observations two to three times to make sure the signal we are seeing is robust and to increase the detection significance' to reduce the chance of a statistical coincidence to less than approximately one in a million.
'Second, we need more theoretical and experimental studies to make sure whether or not there is another abiotic mechanism (one not involving biological processes) to make DMS or DMDS in a planetary atmosphere like that of K2-18 b. Even though previous studies have suggested them (as) robust biosignatures even for K2-18 b, we need to remain open and pursue other possibilities,' he continued.
The findings present significant uncertainty regarding whether the observations are due to living organisms. Madhusudhan cautioned that it benefits no one to declare prematurely that we have found life.
