Astronomers still discover the clearest evidence that life could exist across the solar system from the atmosphere of a planet 124 light years away from Earth, and are paying attention to the rare excitement – attention in the global scientific community.
Using James Webb Space Telescope, researchers led by astronomers at the University of Cambridge in the UK have discovered the chemical characteristics of two compounds produced only by living things on Earth.
“These are probably the first hints we’ll find in the alien world that we might live in,” Nikuku Madhusdan, Cambridge professor of astronomy and the lead researcher behind the discovery, told reporters at a media briefing on April 15.
So, where are the planets that may possibly host life, what evidence did scientists find, and are there any reason for skepticism?
Where did the scientists find this evidence?
Researchers rely on data captured by NASA’s James Webb telescope, which was transported to space in 2022, about 1.5 million kilometers (930,000 miles) from Earth, just like a human watchtower peering into space.
They focus on specific planets K2-18B. This is because it already showed promising signs as an extraterrestrial organism of candidates with the conditions on Earth.
The K2-18b is located in a constellation called Leo and is far from Earth, so the spacecraft must travel for 124 years at the speed of light to get there. In reality, it takes much longer, as the laws of physics do not allow anything other than light to move that fast.
The planet is 8.6 times larger than Earth. Critically, it lies in what is known as the “Goldilocks Zone” of the Sun. It is the area around the star where the planet’s temperature can support liquid water on its surface.
In 2023, astronomers in Cambridge discovered methane and carbon dioxide in the planet’s atmosphere.
It was the first time a carbon-based molecule was discovered in the atmosphere of any planet in the habitable zone of the Sun. Scientists said the first ocean-covered surfaces, and hydrogen-rich atmospheres, explain the existence of carbon-based molecules. Simply put, the planet could have had water.
What did the scientists find now?
Researchers have now discovered more difficult evidence suggesting that the planets not only have conditions to host life, but at least in theory they may host life itself.
To explore planets that have been years away from Earth, scientists wait for them to pass by the sun. They study the light from the sun passing through the atmosphere of these planets and look for clues.
This is how the team found traces of dimethyl sulfide (DMS) or dimethyl disulfide (DMDS) or both in the atmosphere of K2-18b.
On Earth, these compounds are produced only by organisms, especially microorganisms such as marine phytoplankton. What scientists find suggests that the concentration of these chemicals in the K2-18B atmosphere is thousands of times higher than Earth.
In a media statement on the Cambridge University website, co-author Mans Holmberg, a researcher at the Space Telescope Science Institute in Baltimore, USA, said:
How reliable are the survey results?
Scientists published their findings in a peer-reviewed Astrophysics Journal Letters publication. That is, other experts in the field that studied their papers have found it to be compelling.
But that doesn’t mean that scientists have found unrefuted evidence of life. And it’s far from there.
Madhusudhan acknowledged that traces of DMS and DMD found in the atmosphere of K2-18B may be the result of a chemical phenomenon unknown to humanity at this time.
“It’s important that we are deeply skeptical of our outcomes, because once again, it’s only through testing and testing that we can get to where we are confident in them,” Madhusudan said. “That’s how science works.”
His colleagues on the research team agreed.
“Our work is the starting point for all the research needed to confirm and understand the meaning of these exciting discoveries,” says Savesvath Constantine, co-author of the Institute of Astronomy in Cambridge.
The findings from a Cambridge-led team have followed a series of breakthroughs in recent years, and have excited scientists about the possibility of finding life across the globe.
In 2011, NASA scientists announced that they had discovered a chemical that is a component of the DNA of metstone that landed in Antarctica. The chemical traces they discovered would not have been the result of pollution after the metstone landed on Earth. The only explanation – asteroids and comets can contain the components of life.
A year later, astronomers at the University of Copenhagen tracked sugar molecules in distant star systems. The molecule is an important component of ribonucleic acid or RNA, which are important molecules for most biological functions.
In 2023, astronomers found traces of organic molecules in the gas around Enceladus, one of Saturn’s moons.
And in mid-2024, scientists identified five greenhouse gases they said were signs of life on other planets.
However, the science journey is about set-offs as well. In 2005, two NASA scientists claimed they discovered potential traces of extraterrestrial life on Mars after discovering signs of methane there. However, these findings ultimately failed to withstand scientific scrutiny, and NASA distanced themselves from their conclusions.
What’s next?
The Cambridge-led team found 99.7% certainty DMS and DMD. But while that may sound like a near perfect score, it is far from what has been accepted as a benchmark for new discoveries by strict standards of science.
Their conclusions must reach what is called a 5-sigma threshold – 99.9994% certainty in order to be considered bulletproof.
Astronomers believe that more time can help them reach that level of confirmation with James Webb’s telescope.
“Demons from now on, we may look back at this point and realize that it was when the living universe came within reach,” Madhusdan said. “This may be the turning point, where the fundamental question of whether we are alone in the universe is something we can answer.”