The claimed biosignature on K2-18 b
This page delivers no verdict; it presents claims and evidence with their sources. No theory in science is absolute. Method
For everyone
In April 2025 a team announced, based on JWST data, "the strongest hints yet" of dimethyl sulfide (DMS), a gas known on Earth to be produced only by living things, in the atmosphere of the planet K2-18 b. Reanalyses by other teams concluded that the data are not strong enough to show that the gas is present.
For specialists
Madhusudhan and colleagues reported about 3σ significance for DMS and/or DMDS in the MIRI mid-infrared transmission spectrum. Taylor (2025) showed that the MIRI data are statistically indistinguishable from a flat line. Welbanks et al. (2025) showed that Bayesian model comparisons with limited sets of molecules do not amount to a "detection", and that other molecules such as propyne fit equally well or better. A joint analysis of NIRISS, NIRSpec and MIRI data found insufficient evidence for DMS.
Claims
- The atmosphere of K2-18 b contains dimethyl sulfide and/or dimethyl disulfide, which may indicate a biological origin.[1]
Evidence
Supporting
Features in the MIRI spectrum were better explained by models including DMS/DMDS at about 3σ.[1]
Challenging
In a joint analysis of NIRISS, NIRSpec and MIRI data, adding DMS did not significantly increase the Bayesian evidence, and other molecules gave similar fits.[2]
Connections
Sources
- Article (2025). New constraints on DMS and DMDS in the atmosphere of K2-18 b from JWST MIRI. The Astrophysical Journal Letters 983, L40arXiv:2504.12267archive
- Article (2025). Insufficient evidence for DMS and DMDS in the atmosphere of K2-18 b. From a joint analysis of JWST NIRISS, NIRSpec, and MIRI observations. Astronomy & Astrophysicsaanda.orgarchive
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Cite this page
Athena contributors. (2026). The claimed biosignature on K2-18 b. Athena: The tree of human knowledge. Retrieved November 1, 2026, from https://latifkedi.github.io/athena/en/d/k2-18b/
@misc{athena_k2_18b,
title = {The claimed biosignature on K2-18 b},
author = {{Athena contributors}},
year = {2026},
howpublished = {\url{https://latifkedi.github.io/athena/en/d/k2-18b/}},
note = {Athena: The tree of human knowledge. Accessed: 2026-11-01}
}Added: September 27, 2026 · Last changed: September 27, 2026 · Page history