New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI
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 H _2 -rich atmospheres, significantly expands and accelerates the search for habitable environments elsewhere. Rec...
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2025-01-01
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| Online Access: | https://doi.org/10.3847/2041-8213/adc1c8 |
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| author | Nikku Madhusudhan Savvas Constantinou Måns Holmberg Subhajit Sarkar Anjali A. A. Piette Julianne I. Moses |
| author_facet | Nikku Madhusudhan Savvas Constantinou Måns Holmberg Subhajit Sarkar Anjali A. A. Piette Julianne I. Moses |
| author_sort | Nikku Madhusudhan |
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| description | 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 H _2 -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 the carbon-bearing molecules CH _4 and CO _2 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 μ m 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 (≳10 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. |
| format | Article |
| id | doaj-art-5a743b62766743958acdb07be13cfe9d |
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| issn | 2041-8205 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal Letters |
| spelling | doaj-art-5a743b62766743958acdb07be13cfe9d2025-08-20T03:18:02ZengIOP PublishingThe Astrophysical Journal Letters2041-82052025-01-019832L4010.3847/2041-8213/adc1c8New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRINikku Madhusudhan0https://orcid.org/0000-0002-4869-000XSavvas Constantinou1https://orcid.org/0000-0001-6839-4569Måns Holmberg2https://orcid.org/0000-0002-0931-735XSubhajit Sarkar3https://orcid.org/0000-0002-2705-5402Anjali A. A. Piette4https://orcid.org/0000-0002-4487-5533Julianne I. Moses5https://orcid.org/0000-0002-8837-0035Institute of Astronomy, University of Cambridge , Madingley Road, Cambridge, CB3 0HA, UK ; nmadhu@ast.cam.ac.ukInstitute of Astronomy, University of Cambridge , Madingley Road, Cambridge, CB3 0HA, UK ; nmadhu@ast.cam.ac.ukSpace Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USASchool of Physics and Astronomy, Cardiff University , The Parade, Cardiff, CF24 3AA, UKSchool of Physics and Astronomy, University of Birmingham , Edgbaston, Birmingham, B15 2TT, UKSpace Science Institute , Boulder, CO 80301, USAThe 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 H _2 -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 the carbon-bearing molecules CH _4 and CO _2 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 μ m 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 (≳10 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.https://doi.org/10.3847/2041-8213/adc1c8ExoplanetsBiosignaturesHabitable planets |
| spellingShingle | Nikku Madhusudhan Savvas Constantinou Måns Holmberg Subhajit Sarkar Anjali A. A. Piette Julianne I. Moses New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI The Astrophysical Journal Letters Exoplanets Biosignatures Habitable planets |
| title | New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI |
| title_full | New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI |
| title_fullStr | New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI |
| title_full_unstemmed | New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI |
| title_short | New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI |
| title_sort | new constraints on dms and dmds in the atmosphere of k2 18 b from jwst miri |
| topic | Exoplanets Biosignatures Habitable planets |
| url | https://doi.org/10.3847/2041-8213/adc1c8 |
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