Scientists may have found the clearest evidence yet of life beyond our solar system. This discovery comes from the atmosphere of a planet located 124 light-years away from Earth. While the findings have stirred excitement in the scientific world, they also come with a note of caution.
A team of researchers, led by astronomers at the University of Cambridge in the UK, made the discovery using the James Webb Space Telescope. They detected signs of two chemical substances in the planet’s atmosphere that, on Earth, are only produced by living organisms.
Professor Nikku Madhusudhan, an astronomer at Cambridge and the lead author of the study, announced in a press briefing on April 15, “This is the first hint of a potentially life-hosting exoplanet. It’s a revolutionary moment.”
So, where is this possible life-bearing planet? What evidence have scientists found? And is there reason to be skeptical?
The researchers used data collected by NASA’s James Webb Space Telescope, which was launched into space in 2022. The telescope now orbits about 1.5 million kilometers (930,000 miles) away from Earth, acting as humanity’s lookout to observe the universe.
The focus of their research was a specific planet called K2-18b. This planet had already shown signs that it might have Earth-like conditions.
K2-18b is located in a constellation called Leo. It is so far away that even traveling at the speed of light, it would take 124 years to reach it. In reality, the journey would take much longer, as nothing but light can travel that fast, according to the laws of physics.
This planet has a mass 8.6 times greater than Earth’s and is 2.6 times larger in size. It lies in the “Goldilocks zone” of its star — the region where the temperature may allow for liquid water to exist on the surface.
In 2023, Cambridge astronomers detected the presence of methane and carbon dioxide in the planet’s atmosphere.
This marked the first time carbon-based molecules were discovered in the atmosphere of a planet located within the habitable zone of a star — a region that is neither too hot nor too cold. The presence of such molecules means that, in theory, life could be possible. Scientists believe the planet might have a surface ocean covered by a hydrogen-rich atmosphere. This could explain the carbon molecules they found. Simply put, there is a possibility that the planet has water.
The researchers now have strong evidence that the planet not only has conditions suitable for life, but might actually harbor life.
To study planets that are so far away, scientists wait for them to pass in front of their host stars. At that moment, the star’s light passes through the planet’s atmosphere. By analyzing that light, scientists can understand what chemicals are present in the atmosphere.
Using this method, the team found traces of dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) gases in the atmosphere of K2-18b.
On Earth, these compounds are produced only by living organisms, especially microscopic marine creatures called phytoplankton. What’s even more surprising is that the concentration of these compounds on K2-18b could be up to a thousand times higher than on Earth.
Co-author Mans Holmberg, a researcher at the Space Telescope Science Institute in Baltimore, said in a statement, “Watching the results emerge step-by-step, and seeing them stay consistent through deep and independent analysis, has been an extraordinary experience.”
The study has already been published in a peer-reviewed journal — The Astrophysical Journal Letters. That means other experts in the field have reviewed and found the research credible.
However, this doesn’t mean the scientists have found definitive, unshakable proof of life. In fact, they say we’re still far from that.
Professor Madhusudhan acknowledged that the traces of DMS and DMDS found in K2-18b’s atmosphere might also result from chemical processes that we humans don’t yet understand.
He said, “It’s important for us to be deeply skeptical of our own results. Only through repeated testing can we reach conclusions with confidence. That’s how science moves forward.”
His colleagues agree.
Co-author Savvas Constantinou, a scientist at Cambridge’s Institute of Astronomy, said, “Our work is just the first step, from which broader investigations will now begin. These future studies will help us uncover the true significance of this exciting discovery.”
This breakthrough follows a series of major scientific developments in recent years that have raised new hope about the possibility of life beyond Earth.
In 2011, NASA scientists reported finding chemical markers used in DNA on meteorites that fell in Antarctica. These substances weren’t formed due to contamination after arriving on Earth. According to the researchers, these building blocks of life might exist on asteroids and comets.
A year later, astronomers from the University of Copenhagen found a sugar molecule in a distant star system — a crucial ingredient in RNA, which plays an essential role in biology.
In 2023, scientists discovered organic molecules in the gases surrounding Enceladus, one of Saturn’s moons.
And in mid-2024, researchers identified five greenhouse gases that they believe could signal life on other planets.
Still, science often involves trial and error. In 2005, two NASA scientists claimed they had found signs of life on Mars due to the presence of methane gas. But later research failed to confirm the findings, and NASA eventually backed away from the claim.
The Cambridge team says they have identified DMS and DMDS with 99.7% certainty. While that sounds almost perfect, it doesn’t yet meet the strict standard required to be considered a confirmed scientific discovery.
To be fully accepted, a finding must meet the “five-sigma threshold,” which means it must be confirmed with 99.99994% certainty.
The researchers believe they can reach that level of confidence if they are given more time to observe using the James Webb telescope.
Professor Madhusudhan concluded, “Years from now, we might look back and realize this was the moment when the living universe came within our reach. This could be the turning point when we first began to ask — in this vast cosmos, are we truly alone?”