← World catalog MOON / 06
Ganymede
Jupiter
The Solar System's largest moon, with an intrinsic magnetic field and evidence for a deep, layered saltwater ocean.
BEvidence classStrong inference from multiple independent measurements
- Mean radius
- 2,634.1 km
- Surface gravity
- 1.428 m/s²
- Representative temperature
- about −163 °C surface
- Surface pressure
- Extremely tenuous O₂ atmosphere
Scientific assessment
Magnetic and auroral observations support liquid layers, although high-pressure ice may separate the ocean from rock.
- Liquid-water evidence
- Deep subsurface ocean, strong geophysical inference
- Principal constraint
- Deep ocean and possible high-pressure ice barrier
- Principal mission context
- ESA JUICE; Galileo and Hubble archives
Separated context matrix
Six editorial comparison inputs are shown separately. They are not combined into a probability of habitability or life. Conditional research priorities are calculated only in the scenario laboratory with visible assumptions, uncertainty and hard eligibility gates.
Ganymede / System profile
Measured and inferred parameters are labeled by evidence class.
A
Directly observed or repeatedly measured
B
Strong inference from multiple independent measurements
C
Model-dependent or indirect interpretation
D
Unknown or not yet constrained
Interior architecture
A layered physical model from observable surface to uncertain deep interior.
01A
Ancient and grooved terrain
Mixed dark cratered units and younger tectonized ice.
02B
Ice I shell
Cold outer shell caps the deep water system.
03C
Layered ocean and high-pressure ice
Models permit alternating liquid and dense ice phases.
04B
Rocky mantle and metallic core
Differentiation and dynamo imply substantial internal evolution.
Matter and energy pathways
Processes that connect solvent, chemistry, energy and environmental persistence.
1
B Jovian forcing → induction
Time-varying magnetic fields diagnose conductive liquid.
2
C Internal heat → layered water shell
Thermal structure controls liquid and high-pressure ice phases.
Evidence ledger
Claims remain separate from the observations or models that support them.
Intrinsic magnetic field
BasisGalileo magnetometer observations.
Salty subsurface ocean
BasisInduction and Hubble auroral rocking.
Ocean–rock contact
BasisHigh-pressure ice may isolate the main ocean.
Biology
BasisNo ocean-derived sample.
Observation chronology
The measurements and missions that changed the scientific interpretation.
Voyager maps the mixed ancient and grooved surface.
Galileo detects Ganymede’s intrinsic magnetic field.
Hubble aurora observations strengthen ocean evidence.
JUICE will orbit Ganymede after Jovian-system flybys.
Knowledge frontier
Unresolved questions and the observation needed to reduce uncertainty.
Q01C
Is liquid water in contact with rock?
Resolution pathJUICE gravity, magnetic, radar and laser-altimetry data.
Q02C
What powers the present dynamo?
Resolution pathOrbital magnetic mapping and interior modeling.
Competing explanations
The evidence is read against alternatives. A habitable environment, a detectable signal and a biological explanation are separate claims.
Test this world in the scenario simulator →Scientific state vector
Uncertainty and decision laboratory
A reproducible Rust ensemble propagates uncertainty through the declared decision scenario. Results are conditional research priorities, never probabilities of life.
Ready to calculate
Local sensitivity
Knowledge gaps and mission design
The engine ranks uncertainty that can change a decision, then compares mission architectures under explicit resource constraints.
Priority knowledge gaps
Calculating…
Mission architecture sandbox
Calculating…
Comparative research model — not a flight design or cost estimate.