Astronomers using the NASA/ESA/CSA James Webb Space Telescope detected chemical fingerprints of dimethyl sulfide (DMS) and/or dimethyl disulfide (DMD) in the atmosphere of the hyperexterrestrial K2-18b. On Earth, DMS and DMD are produced solely by life, primarily microorganisms such as marine phytoplankton. While unknown chemical processes may be the source of these molecules in the atmosphere of K2-18B, the results are the most powerful evidence that life may exist on planets outside of spores.
K2-18 is a red dwarf about 111 light years away from Leo’s constellation.
The star, also known as Epic 201912552, hosts two giant deplanets: K2-18B and K2-18C.
The K2-18B, first discovered in 2015, has a radius of 2.6 times, about 8.6 times.
The planet orbits the star every 33 days at a distance of about 0.15 Au and has an Earth Similarity Index of 0.73.
It receives 1.28 times the intensity of the Earth’s light, and its equilibrium temperature is 2 degrees Celsius (28 degrees Fahrenheit).
Previous observations of K2-18b identified methane and carbon dioxide in its atmosphere. This was the first time a carbon-based molecule was discovered in the atmosphere of an exoplanet in a habitable zone.
These results were consistent with Hycean’s global predictions. This is an exoplanet covered with habitable oceans under a hydrogen-rich atmosphere.
However, another weak signal suggested that something else could happen with the K2-18B.
Transmission spectra of K2-18B using Webb’s Miri Spectrograph. Image credit: A. Smith/N. Mandhusudhan.
“I wasn’t sure if the signal I saw last time was due to DMS, but that hint alone was so exciting that I used a different instrument to make it look different from the Webb,” said Professor Nikku Madhusudhan, an astronomer at Cambridge University.
Previous tentative DMS inferences were made using Webb’s Niriss (near-infrared imager and slitless spectrograph) and Nirspec (near-infrared spectrograph) instruments.
New independent observations used Webb’s Miri (medium-infrared instrument) in the mid-infrared (6-12 microns) range.
“This is independent evidence using different wavelength ranges of light that do not overlap with previous observations, and not with previous observations. The signal has become stronger and more clear,” Professor Madhusudhan said.
“It was incredible to see results emerge and remain consistent through extensive independent analysis and robustness testing,” added Dr. Måns Holmberg, an astronomer at the Institute of Space Telescope Science.
DMS and DMD are molecules from the same family of chemicals, and both are predicted to be biosignatures.
Although both molecules have spectral features that overlap the observed wavelength range, further observations can help distinguish between the two molecules.
However, the concentration of atmospheric DMS and DMD in K2-18B is very different from Earth, which is generally less than a billionth of a volume.
In the K2-18B, they are estimated to be thousands of times stronger.
“The outcome is exciting, but it’s important to get more data before you claim that life has been discovered in another world,” Professor Madhusdan said.
“The inference of these biosignal molecules raises deep questions about the processes that may be producing them,” says Dr. Subajit Sarkar, an astronomer at Cardiff University.
“They’re the most popular and most popular,” said Dr. Savvas Constantinou, an astronomer at the Institute of Astronomy at Cambridge University.
“It’s important that we are deeply skeptical of our own outcomes, because once again, it’s only through testing and testing that we can get to where we are confident in them. That’s how science works,” Professor Madhusudhan said.
study It was released today Astrophysics Journal Letter.
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Nick Madhusdan et al. 2025. New constraints of atmospheric DMS and DMD of K2-18B from JWST millimeters. apjl 983, L40; doi: 10.3847/2041-8213/ADC1C8
Source: www.sci.news