Spectroscopic Analysis Summary
DMS Detection Confidence
3.4 σ
Probable Biosignature Signal (>3σ)
JWST Integrated SNR
28.3
Base offset noise ~ 35 ppm
Model Fit goodness (χ² / N)
1.12
Consistent with Hycean Atmosphere
Mean Transit Depth
2714 ppm
NIRSpec/NIRISS 0.8–5.0 µm
Physical Interpretation: Exoplanet K2-18 b orbits in the habitable zone of M-dwarf star K2-18. During primary transit, stellar illumination filters through the atmospheric annulus before reaching JWST's NIRSpec & NIRISS instruments.
With 10 ppm Dimethyl Sulfide (DMS) and 8 stacked transits, a distinct absorption band emerges near 3.4 µm alongside CH₄ and CO₂ features. On Earth, DMS is produced almost exclusively by marine phytoplankton, making its detection in a hydrogen-rich Hycean atmosphere a key candidate biosignature requiring continued observations.
Synthetic Model Transmission Line
DMS Molecule Band (2.7–3.5 µm)
Simulated JWST Observations with Error Bars
CO₂ Major Absorption Band (4.2–4.5 µm)