Does the atmosphere of K2-18 b contain dimethyl sulfide?
In plain words
A team using JWST reported hints of dimethyl sulfide, a gas made on Earth almost only by marine life, on the planet K2-18 b. Other teams analyzing the same data find no reliable signal.
Precise statement
K2-18 b is a temperate sub-Neptune ($R \sim 2.6 R_{\mathrm{earth}}, M \sim 9 M_{\mathrm{earth}}$) orbiting an M dwarf, with $\mathrm{CH_4}$ and $\mathrm{CO_2}$ detected by JWST in 2023. Determine whether dimethyl sulfide (and dimethyl disulfide) is present at $\ge 5\sigma$ in JWST NIRISS, NIRSpec and MIRI spectra, and if present, whether abiotic photochemistry or delivery can produce the inferred abundance.
What would settle it
Additional JWST transits analyzed by independent pipelines with agreed systematics treatment, reaching a $5\sigma$ detection or an upper limit below the claimed abundance.
Status in the literature
Unverified note: it names recent work and was partly written without a live literature search; it awaits a check by an editor.
A 2025 MIRI analysis reported about $3\sigma$ evidence for dimethyl sulfide or dimethyl disulfide; independent 2025 reanalyses found no statistically significant evidence, and 2026 papers model the spectrum without dimethyl sulfide.
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