awarehorizon // atlas_record
Europa
A cracked shell of ice, resurfaced from below.
- classification
- Icy moon
- system
- Jupiter system
Europa is the smallest of Jupiter's four Galilean moons. Its surface is a young, fractured plain of water ice, remarkably smooth compared with the heavily cratered faces of most moons — a sign that something beneath keeps renewing it.
- Mean radius
- 1,560.8 km
- Surface gravity
- 1.31 m/s²
- Orbital period
- 3.55 Earth days
- Orbital distance
- 670,900 km from Jupiter (mean)
- Surface temperature
- about −160 °C at the equator, colder at the poles
Only values with an established scientific consensus are listed. Where a quantity is uncertain or model-dependent, it is discussed in the sections below rather than stated as data.
The surface is young
Europa carries very few impact craters. Its ice shell must be reworked on geological timescales far shorter than the age of the solar system.
A conductive layer sits beneath the ice
Europa's response to Jupiter's magnetic field is consistent with an electrically conductive layer near the surface. Salty liquid water is the most widely accepted interpretation.
Tidal flexing supplies energy
Europa's orbital resonance with Io and Ganymede keeps its orbit slightly eccentric, so Jupiter's gravity repeatedly flexes the moon and heats its interior.
Spacecraft imaging
Voyager and Galileo returned images of a crack-covered, nearly crater-free surface, establishing its youth.
Magnetic-field measurements
Galileo's magnetometer recorded an induced magnetic signature during flybys — the fingerprint of a conductive layer responding to Jupiter's rotating field.
Spectroscopy
Reflected-light spectra identify water ice plus non-ice salts and sulphur compounds on the surface.
- How thick is the ice shell?Estimates still range from a few kilometres to tens of kilometres.
- Does the subsurface ocean contact a rocky seafloor, which would allow chemical exchange?This is a hypothesis, not an observation.
- Are the reported water-vapour plumes real and persistent?Detections remain contested.
Items above are unresolved. Hypotheses are labelled as such and are not presented as confirmed findings.