A gropu of astronomers announced on April 16, 2025, that in the process of studying a planet around another star, they had found proves for an non awaited atmospheric gas. On Earth, that gas – called dimethyl sulfide – is mostly produced by living organisms. In April 2024, the James Webb Space Telescope began at the host star of the planet K2-18b for almost six hours. During that time, the orbiting planet passed in front of the star. Starlight filtered through its atmosphere, carrying the fingerprints of atmospheric molecules to the telescope.
Throough comparing those fingerprints to 20 diverse molecules that they would potentially await to study in the atmosphere, the astronomers ended up with the most probable match was a gas that, on Earth, is a good indicator of life. Read on to know all details.
K2-18b, a mysterious world
To comprehend what this discovery truly implies, let’s beging with the bizarre world it was found in. The planet’s name is K2-18b, which means that it is the first planet in the 18th planetary system found by the extended NASA Kepler mission, K2. Astronomers assign the “b” label to the first planet in the system, not “a,” to avoid any type of confusion with the star.
Although astronomers know very little about K2-18b, we are conscious about that it is very unlike Earth. To start, it is about eight times more massive than Earth, and it has a volume that’s about 18 times larger. This explains that it’s only about half as dense as Earth. In other words, it must have a lot of water, which isn’t very dense, or a very big atmosphere, which is even less dense.
In addition astronomers stipulat that this world could either be a smaller version of our solar system’s ice giant Neptune, named as mini-Neptune, or maybe a rocky planet with no water but a massive hydrogen atmosphere, called a gas dwarf. Another option, as University of Cambridge astronomer Nikku Madhusudhan recently suggested, is that the planet is a “hycean world.”
Detecting DMS: how the story continues
In 2023, Madhusudhan and his colleagues used the James Webb Space Telescope’s short-avelength infrared camera to study starlight that filtered through K2-18b’s atmosphere for the first time. They found evidence for the presence of two simple carbon-bearing molecules – carbon monoxide and methane – and proved that the planet’s upper atmosphere lacked water vapor.
Mashusudhan’s team turned JWST back to K2-18b a year later. This time, they used another camera on JWST that looks for another range of wavelengths of light. The brand new results – announced on April 16, 2025 – supported their initial findings. It must be highlited that these new data show a stronger – but still relatively weak – signal that the team attributes to DMS or a very likely molecule. The fact that the DMS signal showed up on another camera during another set of observations made the interpretation of DMS in the atmosphere stronger.
