New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI

2025/04/16 by Nikku Madhusudhan, Madhusudhan, Nikku, Savvas Constantinou +9 · 35 voices · 16 citations
Physics and Astronomy · #Astrophysics and Star Formation Studies #Stellar, planetary, and galactic studies #Astro and Planetary Science

paper · pdf · doi:10.48550/arxiv.2504.12267

Abstract

The sub-Neptune frontier has opened a new window into the rich diversity of planetary environments beyond the solar system. The possibility of hycean worlds, with planet-wide oceans and H₂-rich atmospheres, significantly expands and accelerates the search for habitable environments elsewhere. Recent JWST transmission spectroscopy of the candidate hycean world K2-18 b in the near-infrared led to the first detections of carbon-bearing molecules CH₄ and CO₂ in its atmosphere, with a composition consistent with predictions for hycean conditions. The observations also provided a tentative hint of dimethyl sulfide (DMS), a possible biosignature gas, but the inference was of low statistical significance. We report a mid-infrared transmission spectrum of K2-18 b obtained using the JWST MIRI LRS instrument in the ~6-12 μm range. The spectrum shows distinct features and is inconsistent with a featureless spectrum at 3.4-σ significance compared to our canonical model. We find that the spectrum cannot be explained by most molecules predicted for K2-18 b with the exception of DMS and dimethyl disulfide (DMDS), also a potential biosignature gas. We report new independent evidence for DMS and/or DMDS in the atmosphere at 3-σ significance, with high abundance (\gtrsim10 ppmv) of at least one of the two molecules. More observations are needed to increase the robustness of the findings and resolve the degeneracy between DMS and DMDS. The results also highlight the need for additional experimental and theoretical work to determine accurate cross sections of important biosignature gases and identify potential abiotic sources. We discuss the implications of the present findings for the possibility of biological activity on K2-18 b.

Citations

• Carbon-bearing Molecules in a Possible Hycean Atmosphere
• Spectroscopic Time Series Performance of the Mid-infrared Instrument on the JWST
• ArXiv
• Exoplanet Biosignatures: A Review of Remotely Detectable Signs of Life
• <tt>batman</tt>: BAsic Transit Model cAlculatioN in Python
• emcee : The MCMC Hammer
• HITEMP, the high-temperature molecular spectroscopic database
• The James Webb Space Telescope
• The Mid-Infrared Instrument for the<i>James Webb Space Telescope</i>, IV: The Low-Resolution Spectrometer

Cited by

• A Narrowband Technosignature Search Toward the Hycean Candidate K2-18b Using the VLA and MeerKAT
• K2-18b Does Not Meet The Standards of Evidence For Life
• The Detection-versus-retrieval Challenge: Titan as an Exoplanet
• A Systematic Search for Trace Molecules in the Atmosphere of Exoplanet K2-18 b
• Challenges in the detection of gases in exoplanet atmospheres
• A Comprehensive Reanalysis of K2-18 b's JWST NIRISS+NIRSpec Transmission Spectrum
• A JWST Transmission Spectrum of the Temperate Sub-Neptune TOI-732 c
• Plan 9: Detecting Atmospheric Deterrence Against Interstellar Monsters
• Is the high-energy environment of K2-18b special?
• Bayesian Model Comparison and Significance: Widespread Errors and how to Correct Them
• Not All Sub-Neptune Exoplanets Have Magma Oceans
• JWST-TST DREAMS: Sulfur dioxide in the atmosphere of the Neptune-mass planet HAT-P-26 b from NIRSpec G395H transmission spectroscopy
• Hydrocarbon Hazes on Temperate sub-Neptune K2-18b supported by data from the James Webb Space Telescope
• Bayesian inference [wikipedia]
• Hycean planet [wikipedia]
• K2-18b [wikipedia]
• 2025 [wikipedia]

Discussions

• OK, so I read the journal paper about finding "biosignatures" in the atmosphere of the nearby planet K2-18b. Quick take: the detection of the molecules looks fine. May be real, may not be, but let's s [bsky, 344 points, 22 comments]
• Alien life? Planet K2-18b has dimethyl sulfide in its atmsophere. On Earth that comes from marine microorganisms. Not proof, but as Spock would say, fascinating. Artist's image: Joseph Olmsted arxiv.o [bsky, 165 points, 13 comments]
• About that new paper on K2-18b, which headlines with "Scientists hail ‘strongest evidence’ so far for life beyond our solar system," evidently prodded by a Cambridge U. press release. arxiv.org/pdf/25 [bsky, 69 points, 2 comments]
• Has JWST found life on another world? 🔭 An analysis of exoplanet K2-18 b points to the existence of dimethyl sulfide, a molecule produced by photosynthesizing plankton on Earth—but proving that this [bsky, 48 points, 2 comments]
• Here’s the paper: arxiv.org/abs/2504.12267 (22/n) [bsky, 46 points, 1 comments]
• The K2-18b paper is now up as a preprint (to be followed by the final paper soon) arxiv.org/abs/2504.12267 [bsky, 27 points, 4 comments]
• The K2-18 b paper just dropped. I will say, the peaks at ~9.8 microns *do* look pretty convincing, so this may very well be a high-confidence detection of DMS. However, given that's there still debate [bsky, 27 points, 2 comments]
• El JWST confirma la presencia de dimetilsulfuro y/o dimetildisulfuro (alrededor de 3-σ) en el exoplaneta K2-18b arxiv.org/pdf/2504.12267 [bsky, 26 points, 5 comments]
• will read this in more detail in the morning but a quick thread of some technical quirks: for context, "sigma"/confidence intervals here describe the preference of one model/hypothesis over another, n [bsky, 21 points, 1 comments]
• Wait, is this the paper? I'm pretty sure it is, unless I am mistaken? (someone check?!) arxiv.org/abs/2504.12267 [bsky, 20 points, 2 comments]
• Fonte: arxiv.org/pdf/2504.12267 [bsky, 17 points, 0 comments]
• 🧪 Une nouvelle étude suggère (à 3σ) la présence de DMS et DMDS dans l'atmosphère de l'exoplanète K2-18b. Sur Terre, ces molécules ne sont produites que par des bactéries et du plancton, ce qui pourra [bsky, 13 points, 2 comments]
• There is a paper now! arxiv.org/pdf/2504.12267 [bsky, 13 points, 1 comments]
• This is sooooooooo exciting. Could go away with more data but it’s exactly the kind of path we’d expect on the road finding life. arxiv.org/abs/2504.12267 [bsky, 10 points, 3 comments]
• 2) L'espectre de transmissió de la seva atmosfera és certament interessant i denota una complexitat molecular rellevant. Veurem fins a quin punt els models són unívocament vàlids. Paga la pena llegir [bsky, 7 points, 1 comments]
• arxiv.org/pdf/2504.12267 [bsky, 6 points, 1 comments]
• Trump vs. the Fed, briefly explained [lemmy, 4 points, 0 comments]
• New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI arxiv.org/abs/2504.12267 [bsky, 4 points, 1 comments]
• Today on the #arXiv : Madhusudhan et al. 2025, "New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI" - arxiv.org/pdf/2504.12267 I am not convinced by a claimed 3-sigma excursio [bsky, 2 points, 2 comments]
• arxiv.org/abs/2504.12267 [bsky, 1 points, 1 comments]
• Wat is er niet serieus aan dit onderzoek? Analyse van de meetgegevens van ruimtetelescoop Webb. Metingen interpreteren. En waarom denigrerend dit astrologie noemen? Ik neem jou niet serieus met zo'n o [bsky, 1 points, 1 comments]
• arxiv.org/abs/2504.12267 [bsky, 1 points, 0 comments]
• You can read the research paper on the possible detection of molecules that possibly indicate life on another planet here arxiv.org/abs/2504.12267 [bsky, 1 points, 1 comments]
• Ah, by the way, concerning the recent claims about signatures for molecules related to life on exoplanet K2-18b If you feel like inquring beyond the hyped press releases, here's the original preprint! [bsky, 1 points, 0 comments]
• Not a definitive sign of life, but a POSSIBLE biomarker. How we are searching for life in the universe is fascinating - scanning distant atmospheres for whisps of biology. Perhaps there is an ocean of [bsky, 1 points, 0 comments]
• now on arxiv arxiv.org/pdf/2504.12267 [bsky, 1 points, 0 comments]
• Today on the # arXiv : Madhusudhan et al. 2025, "New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI" - https:// arxiv.org/pdf/2504.12267 I am not convinced by a claimed 3-sigm [mastodon, 0 points, 2 comments]
• Sources: The figure is from this preprint of the paper arxiv.org/abs/2504.12267 The quotation is from this press release www.cam.ac.uk/stories/stro... [bsky, 0 points, 0 comments]
• arxiv.org/abs/2504.12267 [bsky, 0 points, 0 comments]
• methinks current news follow a paper published yesterday that reports better evidence for DMS in the atmosphere than the previous [bsky, 0 points, 0 comments]
• New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI: arxiv.org/abs/2504.12267 -> Strongest hints yet of biological activity outside the solar system: www.eurekalert.org/news-re [bsky, 0 points, 1 comments]
• This is the IoA paper that's in the news this morning: arxiv.org/abs/2504.12267 [bsky, 0 points, 0 comments]
• Nieuwe artikel arxiv.org/abs/2504.12267 Zelfs als ze het met 5 sigma hadden gevonden, was het nog geen duidelijk teken van leven, helaas. DMS kun je ook op andere manieren krijgen. [bsky, 0 points, 1 comments]
• « La possibilité de mondes hycéens, avec des océans à l'échelle de la planète et des atmosphères riches en H2, élargit considérablement et accélère la recherche d'environnements habitables ailleurs. » [bsky, 0 points, 1 comments]
• here it is: arxiv.org/abs/2504.12267 [bsky, 0 points, 1 comments]

Related

• New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI
• A Systematic Search for Trace Molecules in the Atmosphere of Exoplanet K2-18 b
• K2-18b Does Not Meet The Standards of Evidence For Life
• Insufficient evidence for DMS and DMDS in the atmosphere of K2-18 b
• A Comprehensive Reanalysis of K2-18 b's JWST NIRISS+NIRSpec Transmission Spectrum