dimethyl disulfide Archives

The volume mixing ratios of key gases in the Hycean and sub-Neptune atmospheres, averaged across 0.1 – 10−5 bar to represent the expected abundances of photochemical products probed by transmission spectroscopy. CH4 and CO2 are prescribed manually at the lower boundary in the Hycean model, and the DMS distribution is also imposed for our consistency tests, as described in Sections 3.2.1 and 3.2.2. -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Ice Giant, Imaging & Spectroscopy, Status Report

Three Outstanding Physical Questions For K2-18 b And Other Temperate sub-Neptunes

by Keith CowingMarch 24, 2026June 11, 2026

Recent transmission spectra of the temperate sub-Neptune K2-18 b obtained with JWST have attracted significant attention. Debates have quickly arisen over the interpretation of the spectral data, particularly the recent […]

Retrieval results on the full spectrum for three difference MIRI pixel shifts. The top panel shows the transit spectrum with the median retrieved spectral model and representative 1σ and 2σ credibility envelopes. The lower subpanels show the inferred 1D marginalized posterior distributions for the isothermal temperature (T), CH4, CO2, C2H4, DMS, DMDS, and C2H5Cl. -- The Astronomical Journal

Astronomy & Telescopes, Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Status Report, Venus

Sub-Neptune Exoplanet K2-18b Does Not Meet the Standards Of Evidence For Life

by Keith CowingOctober 9, 2025

K2-18b, a temperate sub-Neptune, has garnered significant attention due to claims of possible biosignatures in its atmosphere. Low-confidence detections of dimethyl sulfide (DMS) and/or dimethyl disulfide (DMDS) have sparked considerable […]

NIRISS/SOSS and NIRSpec/G395H transit spectrum of K2-18b. The spectrum matches that published by M23 after applying a -50 ppm offset to their spectrum. -- astro-ph.EP

Astrochemistry, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Status Report

K2-18b Does Not Meet The Standards Of Evidence For Life

by Keith CowingAugust 11, 2025August 11, 2025

Transmission spectra of K2-18 b from exoTEDRF (blue), JExoRES (black), SPARTA (orange) and Eureka! (green). For NIRISS and NIRSpec, faded points show higher resolution (R=100 and 200, respectively) spectra, and solid colors are binned for clarity. Smaller panels show error-normalized differences relative to exoTEDRF. The JExoRES spectra used different binning and are interpolated in the difference panels. -- astro-ph.EP

Astrochemistry, Astrogeology, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report, Venus

Insufficient Evidence For DMS And DMDS In The Atmosphere Of K2-18 b

by Keith CowingMay 20, 2025September 18, 2025

Recent JWST observations of the temperate sub-Neptune K2-18 b have been interpreted as suggestive of a liquid water ocean with possible biological activity. Signatures of DMS and DMDS have been […]

Contributions of molecules in the JWST MIRI range for the transmission spectrum of K2-18 b, assuming 1% CO2 and CH4, and 10−5 by volume for each of DMS, diethyl sulfide, methacrylonitrile, trans-2-pentene, 2-butene and propyne. -- astro-ph.EP

Astrochemistry, Astronomy & Telescopes, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Status Report

A Systematic Search for Trace Molecules in Exoplanet K2-18 b

by Keith CowingMay 16, 2025May 16, 2025

The first transmission spectrum of the habitable-zone sub-Neptune K2-18 b with JWST has opened a new avenue for atmospheric characterisation of temperate low-mass exoplanets.

Absorption cross-sections in the JWST/MIRI LRS wavelength range for dimethyl sulfide, dimethyl disulfide, and a selection of the hydrocarbons considered in our model exploration. -- astro-ph.EP

Astronomy & Telescopes, Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

The Challenges of Detecting Gases in Exoplanet Atmospheres

by Keith CowingMay 1, 2025May 1, 2025

Claims of detections of gases in exoplanet atmospheres often rely on comparisons between models including and excluding specific chemical species.

Astrochemistry, Astrogeology, Astronomy & Telescopes, Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Press Release

Strongest Hints Yet Of Biological Activity Outside Our Solar System

by Keith CowingApril 17, 2025April 17, 2025

Astronomers have detected the most promising signs yet of a possible biosignature outside the solar system, although they remain cautious. Using data from the James Webb Space Telescope (JWST), the […]