K2-18b. A planet that might be breathing.
A fictional three-level communication of a real JWST discovery as a use case for science communication. How a platform can work when the same fact must be told for child, curious adult and scientist.
K2-18b. A planet that might be breathing.
A fictional three-level communication of a real JWST discovery as a use case for science communication. How a platform can work when the same fact must be told for child, curious adult and scientist.
A discovery, told for three levels.
What this service is
Science as a service: making the same discovery available at three depths, without one depth banalising the others. The six-year-old should marvel. The curious adult should understand. The researcher should recognise.
The subpage shows this using JWST observations of the exoplanet K2-18b. A real discovery with real scientific controversy. Three levels, one data foundation, one switch.
Three levels
Explorer · Expander · Explainer in a switch
Spectrum
Adaptive per level, with sigma bands
Confidence
2σ tentative · 3σ hint · 5σ detection
Library
DOI, abstract, BibTeX ready to cite
What it fits, what it doesn't
- research with tiered communication for school, public, expert
- topics with honest uncertainty and real debate
- institutions that demand scientific correctness
- education initiatives across several age groups
- reduced science messages at only one level
- topics without a robust peer-reviewed foundation
- communication that fakes consensus where there is none
- platforms without dedicated scientific oversight
The starting point
A university, a planetarium and a national research funder want to communicate a current discovery. The headline writes itself. But the story behind it is complex, honestly controversial, full of methodological detail.
What if the same discovery were accessible in three depths in one place. With a switcher between levels. With a spectrum that is simplified or full depending on level. With a library of papers for those who want to dig deeper.
What follows is this three-level communication as a sketch.
Artist's concept of a Hycean world surface · not a real image
Three levels, one atmosphere
JWST measured molecules in the atmosphere of exoplanet K2-18b whose presence on Earth is tightly linked to life. What this really means depends on the level at which you look.
K2-18b · sub-Neptune, 2.6 Earth radii
33 days · habitable zone
K2-18 · red dwarf
124 light years · constellation Leo
The path of a discovery
Science happens over time, with detections, follow-up studies, re-analyses, replications. Click a station to jump to the matching publication in the library.
- 2015
Discovery
K2-18b first identified in Kepler K2-Mission data (Montet et al.).
- 2019
Water-vapour hint
Hubble observations show first hints of H₂O in the atmosphere (Tsiaras et al., Nature Astronomy).
- 2021
Hycean framework
Theoretical classification of 'Hycean worlds' is published (Madhusudhan & Piette).
- 2023 · September
First DMS hint
JWST · NIRISS and NIRSpec detect a signal consistent with dimethyl sulphide, 3σ.
- 2025 · April
MIRI follow-up
Mid-infrared data raise the DMS / DMDS hints to 3 - 3.5σ.
- 2025 · August
Independent re-reduction
Schmidt et al. re-reduce the MIRI data. The DMS signature drops below detection threshold.
- 2026
Replication in flight
JWST Cycle 4 observations with MIRI-LRS to replicate the 9 - 11 μm band are scheduled.
- 2027
Expected resolution
Consensus from the 2025 conference sessions: 2027 should either harden or close the DMS question.
As of June 2026. Sources NASA ADS and arXiv. The list is updated continuously.
Content, spectrum diagram and vocabulary change with each level.
K2-18b is a sub-Neptune, about 2.6 Earth radii, in the habitable zone of a red dwarf star. James Webb clearly detected water vapour, methane and CO₂ in its atmosphere.
In 2023 a team around Madhusudhan in Cambridge reported first hints of dimethyl sulphide, DMS. On Earth DMS is almost exclusively produced by plankton. If it could be detected off-Earth, that would be a first-rank biosignature.
A follow-up study in April 2025 using the mid-infrared instrument MIRI reported again signals compatible with DMS and DMDS, with higher confidence than before.
In 2025 a NASA-coordinated re-analysis showed that the statistical evidence is not sufficient for a secure detection. DMS can also form without life, for instance in comets or via UV chemistry. The debate is open.
What is certain: today we can chemically interrogate the air of a planet over a hundred light years away. That we argue how to interpret the spectrum is a sign that science is working.
Water, methane, CO₂ clearly detected.
DMS / DMDS reported, statistically uncertain.
Hycean world hypothesis exists but is not established.
Transit spectroscopy · the measurement process
How a 1 % brightness dip at 1.4 μm becomes a chemical inventory of an atmosphere.
Transit geometry
K2-18b crosses the line of sight between us and K2-18 every 33 days. The geometry is a rare alignment.
Atmospheric filter
During transit a thin annulus of starlight grazes the upper atmosphere. Molecules there absorb at their own wavelengths.
Wavelength-dependent depth
Transit depth varies subtly with wavelength. That difference, normalised to the star, gives the transmission spectrum.
Molecule identification
Comparison with model spectra gives mixing ratios. The spectrum tells us what is in the air.
Transit spectroscopy · the method behind it
When K2-18b transits K2-18, its atmosphere filters a tiny fraction of the starlight. Different molecules leave absorption signatures at characteristic wavelengths.
- H₂Obelegt7.0σWater vapour · ~1.4 μm
- CH₄belegt6.0σMethane · ~2.3 μm and 3.3 μm
- CO₂belegt5.0σCarbon dioxide · ~4.3 μm
- DMSvorläufig3.3σDimethyl sulphide · 9 - 12 μm (MIRI)
- DMDSumstritten2.8σDimethyl disulphide · co-detected
- NH₃umstritten1.5σUpper limit · argues against Hycean
Astronomical convention: 3σ counts as a hint, 5σ as a secure detection. Values for K2-18b after Madhusudhan 2023 + 2025, Schmidt 2025, Tsiaras 2019.
Four questions science is resolving now
Scientifically, open is the most important state. These are the four most concrete outstanding questions on K2-18b research, as of June 2026.
Is DMS really there?
An independent MIRI-LRS replication in JWST Cycle 4 is scheduled. Resolution of the 3 - 3.5σ signature expected 2026 / 2027.
Which abiotic sources can produce DMS?
Cometary contributions, photo-dissociation cascades and mineral-catalysed reactions are plausible but insufficiently modelled. Lab astrochemistry 2025 - 2027 pending.
Is K2-18b really a Hycean world?
The Hycean scenario requires a liquid ocean under an H₂ atmosphere. The absence of clear NH₃ signatures argues against. Alternative: mini-Neptune without surface.
Which other sub-Neptunes are similar?
Comparison objects of the same spectral class (e.g. TOI-270d, GJ 9827d) are being observed in JWST Cycle 3 + 4. A comparative study is expected in 2027.
Science library
The primary literature on the K2-18b debate with DOI, abstract snippet, replication status and cite function. Click an event in the timeline above to jump to the matching card.
- PEER-REVIEWEDReproducedNature Astronomy
Water vapour in the atmosphere of the habitable-zone eight-Earth-mass planet K2-18b
Tsiaras et al. · 2019
ABSTRACTFirst detection of water vapour in the atmosphere of an exoplanet within the habitable zone of its star. Hubble WFC3 transmission spectrum reveals statistically significant absorption features consistent with H₂O.
- PEER-REVIEWEDReproducedApJ
Habitability and biosignatures of Hycean worlds
Madhusudhan, Piette & Constantinou · 2021
ABSTRACTTheoretical framework introducing the Hycean world taxonomy. Defines a class of habitable sub-Neptunes with H₂-rich atmospheres above liquid water oceans. Provides expected biosignature inventory.
- PEER-REVIEWEDPartially reproducedApJL 956:L13
Carbon-bearing molecules in a possible Hycean atmosphere
Madhusudhan et al. · 2023
ABSTRACTJWST NIRISS and NIRSpec transmission spectrum of K2-18b shows robust detections of CH₄ and CO₂ and a tentative inference of dimethyl sulfide (DMS) at the 3σ level. DMS on Earth is produced almost exclusively by marine phytoplankton.
- PEER-REVIEWEDPartially reproducedApJL 982:L40
New JWST MIRI-LRS observations of K2-18b
Madhusudhan et al. · April 2025
ABSTRACTMIRI-LRS transmission spectrum of K2-18b in the 6 - 12 μm range. Independent detection of features consistent with DMS and DMDS at combined 3 - 3.5σ confidence. Best-fit log mixing ratio log10(DMS) ≈ -4.5.
- PREPRINTNot reproducedarXiv:2508.05961
Independent reduction of the MIRI-LRS spectrum of K2-18b
Schmidt, Mathur et al. · August 2025
ABSTRACTIndependent re-reduction of MIRI-LRS data with alternative pipelines and stellar-contamination corrections. The DMS / DMDS signature is consistent with detector systematics. Conservative CI lower bound below 5σ detection threshold.
Artist's concept · K2-18b transiting K2-18 · not a real image
A science that grows with us
The science around K2-18b continues. JWST observations 2026 / 2027 will either harden or close the DMS question. Madhusudhan, Schmidt and other teams work in parallel on different analyses. NASA prioritises replication.
What I contribute here as a science service: a space where the same research is accessible at the same time to a six-year-old classroom, a curious mother and an astrophysicist, without any of the three depths banalising the others. No closing word. A communication infrastructure that grows as the next study arrives.
How I would build it
Four phases, scientific oversight in the core, not as appendix.
Understand
Conversations with the research team, with didactics specialists for the youngest level, with science journalism. What remains true at each level, what tips into falsehood?
Define levels
Concretely formulate three levels, parallel test texts, test with audiences. Sketch the spectrum diagram in three layers. Decision gate for the host organisation.
Build
Frontend with a switcher component that changes content and diagram in sync. Spectrum as parametric SVG with detail layers that can be shown / hidden. Library with paper references linked at Explainer level.
Maintain
With ongoing research, regular updates. Versioning of level texts, surface when what changed. Scientific oversight mandated, not voluntary.
Scientific foundation
All numbers, confidences and statements cited here come from peer-reviewed or peer-review-oriented literature and are linked directly at Explainer level.
- Madhusudhan et al. 2023 · Carbon-bearing molecules in K2-18b atmosphere · ApJL
- Madhusudhan et al. 2025 · MIRI observations of K2-18b · ApJL 982:L40
- Schmidt et al. 2025 · Re-reduction of MIRI K2-18b data · arXiv 2508.05961
- NASA · Exoplanet Archive · K2-18 system parameters
- Astronomy.com · New study revisits signs of life on K2-18b
- K2-18b · Wikipedia · system overview
Spectrum as scrollytelling
The electromagnetic spectrum as a narrative journey. Exactly the scientific instrument JWST uses on K2-18b.
Three depths, one truth
If your research has to land at school, public and expert at the same time, without one depth banalising the others, get in touch.