In an important discovery, scientists using the James Webb Space Telescope (JWST) have found signs that may suggest life beyond our solar system. They were observing a distant planet called K2-18 b and found two special gases—dimethyl sulphide (DMS) and dimethyl disulphide (DMDS)—in its atmosphere. On Earth, these gases are only made by living organisms, especially by small marine life like algae.

This doesn't confirm there is life on the planet, but it shows a biosignature—a chemical that might be made by living beings. The scientists say more research is needed to be sure. But this is still a big moment in science.

Astrophysicist Nikku Madhusudhan, from the University of Cambridge’s Institute of Astronomy, who led the study, said,
"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."

He added that while there are many missions to find signs of life in our solar system, like on Mars, Venus, and icy moons, this is one of the first promising signs from a planet so far away.

K2-18 b is a large planet, about 8.6 times heavier than Earth and 2.6 times wider. It orbits a small red dwarf star in the “habitable zone”—this is the perfect distance from its star where water can exist in liquid form, which is necessary for life.

This planet is around 124 light-years away from Earth, in the constellation Leo. (One light-year is about 9.5 trillion kilometres.) Another planet also orbits the same star, but K2-18 b is the main focus for now.

Could this planet really support life?

K2-18 b is believed to be a “Hycean world”—a planet that is covered in oceans and has a hydrogen-rich atmosphere. Scientists think this kind of world could support microbial life, similar to tiny organisms found in Earth’s oceans. It may even be warmer than Earth’s oceans.

Earlier studies using the same telescope had already found carbon-based molecules like methane and carbon dioxide in the planet’s atmosphere. Now, the detection of DMS and DMDS adds even more hope.

"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."

He also explained that when we talk about life on such planets, it would most likely be microbial life—basic life forms, not complex animals or humans.
"We won't be able to answer this question at this stage. The baseline assumption is of simple microbial life," he said when asked about the possibility of intelligent life.

Webb found the presence of DMS and DMDS with 99.7% confidence. That means there is still a 0.3% chance this could be a mistake or just noise in the data. The amounts of these gases in the planet’s atmosphere are also very high, over 10 parts per million, thousands of times higher than on Earth.
"This cannot be explained without biological activity based on existing knowledge," Madhusudhan said.

How do scientists find chemicals on faraway planets?

To detect the gases, scientists used a method called the transit method. This happens when a planet passes in front of its star from Earth’s point of view. Some light from the star goes through the planet’s atmosphere, and the telescope picks it up. By studying this light, scientists can figure out which gases are present.

This new observation from JWST used a different instrument and studied a new range of light waves compared to earlier studies. Even in the past, Webb had given a small clue about DMS. But this time, the signals are much stronger.

K2-18 b belongs to a group of planets called sub-Neptunes—bigger than Earth but smaller than Neptune, which is a gas planet in our solar system.

Since the 1990s, about 5,800 such exoplanets (planets outside our solar system) have been discovered. Scientists have long hoped to find life on one of them, and K2-18 b is now one of the most promising.

Still, experts are urging caution.
Christopher Glein, a top scientist at the Southwest Research Institute in Texas, said:
"The rich data from K2-18 b make it a tantalising world. These latest data are a valuable contribution to our understanding. Yet, we must be cautious 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."

Madhusudhan agreed that scientists should not jump to conclusions.
"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," he said.

They also need to check if there could be non-biological ways for these gases to form on such a planet.

"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 said.
"It is in no one's interest to claim prematurely that we have detected life," Madhusudhan added.

So, while we may be close to answering the question—"Are we alone in the universe?"—scientists say we must be patient and keep studying the data. This could be the beginning of a new chapter in the search for life beyond Earth.

 

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