Interactive globe of the largest moon in the solar system — larger than Mercury, the only moon with an intrinsic magnetic field, and the primary target of ESA's JUICE, which enters orbit around it in 2034 as the first spacecraft ever to orbit another planet's moon. The base is the USGS controlled global mosaic assembled from Voyager 1/2 and Galileo SSI imaging at 1 km/px. The surface records its own history in two terrains: ancient dark cratered regiones covering a third of the moon, and the younger bright grooved sulci that sliced through them — extension recorded in ice. Beneath both, induction measurements require a saline subsurface ocean.
The sphere is rendered in Three.js at Ganymede's mean radius, 2634.1 km, scaled to scene units. The base map is the USGS Astrogeology controlled global mosaic, built from Voyager 1, Voyager 2 and Galileo SSI imaging at 1 km/px — the same product family as the Europa and Io globes, and the best global cartography of Ganymede until JUICE. The product is greyscale; a single uniform tint at Ganymede's mean colour is applied, so all structure in the rendered brightness originates in the data. Source resolution varies strongly across the mosaic (~400 m/px under the best Galileo coverage to tens of km/px in gap fill), and the seams are left visible rather than blended away.
The entries in Data/worlds/ganymede/features.json are drawn from the USGS Gazetteer: the great dark regiones (Galileo, Marius, Nicholson, Perrine), the bright sulci that record global extension (Uruk, Tiamat, Dardanus, Nun), the ray craters Tros and Osiris, the palimpsest Memphis Facula, the crater chain Enki Catena — a comet disrupted like Shoemaker–Levy 9, caught in the act of serial impact — and Gilgamesh, the largest well-preserved impact basin on any icy moon. Ganymede's names follow Near-Eastern mythology and the discoverers of the Jovian system.
Ganymede is synchronous: one rotation per 7.155-day orbit, tidally locked with the sub-Jupiter point at 0° longitude. The idle rotation renders that period's sense. The research panel queries body_server.py at /api/ganymede/latest; absent a server, the seed research.json and ADS search links are used. The engine, server and data schema are shared with the other Worlds globes.