JWST Spectral Archaeologist

Observatory Online — Target: K2-18 b

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K2-18 b

Habitable Zone Candidate

Distance 124 ly

Radius 2.61 R⊕

Mass 8.63 M⊕

Temperature 255 K

Host Star Red Dwarf (M2.5 V)

Discovered 2015

JWST Key Findings NIRISS · NIRSpec

Carbon-bearing molecules CH₄ and CO₂ detected (2023)
Low NH₃ / CO abundances — consistent with an ocean under a H₂ envelope
Tentative dimethyl sulfide (DMS / DMDS) signal reported (2025) — unconfirmed

Observation Parameters

Observation Mode

Integration Time: 2.5 hours

Quick Look Deep Field

📡 Spectral Decoder — Transit Spectroscopy

Toggle Molecular Signatures

Signal-to-Noise 9.2

Active Channels 5

🌑 Transit Simulator

⚫ Out of Transit — Baseline

Transit Depth 0.000%

Orbital Phase 0.0°

🌍 Habitability Assessment

Promising Biosphere Candidate

Liquid Water Potential 40/40

Atmospheric H₂O 25/25

Biosignature Markers 30/30

Temperature Range 15/15

Spectral Confidence

77%

⚠️ Tentative Biosignature

A dimethyl sulfide (DMS) channel is active for K2-18 b. On Earth this compound is produced almost exclusively by marine phytoplankton. The signal is tentative and requires confirmation with additional transit observations.

🧅 Atmospheric Cross-Section

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Temperature Profile

Probe Position