Saturn · natural satellite

Iapetus

Two very different hemispheres

Iapetus has a dark leading hemisphere, brighter terrain on its trailing side and a prominent equatorial ridge. Cassini photographed the contrast at close range.

Mean diameter: 1,468.6 km
Mean orbital distance: 3,561,700 km from centre
Orbital period: 79.331 Earth days

Iapetus · NASA spacecraft imagery — NASA/JPL-Caltech/Space Science Institute · Image source ↗

Compared with our Moon

Iapetus · 1,468.6 km

Moon · 3,474.8 km

One diameter scale. Circle shapes compare volume-equivalent diameters; irregular moons are not spheres.

Orbit & discovery

Surface gravity: 0.224 m/s²
Discovery: 1671
Discoverer / team: G.D. Cassini
Provisional designation: —
JPL satellite ID: 608
Orbital eccentricity: 0.028
Inclination: 7.6 degrees

Inclination reference: Laplace. Mean-element epoch: 2000-01-01.5 TDB · SAT441.

Diameters use volume-equivalent mean radii, including for irregular bodies. Mean orbital elements describe an orbit; they are not live positions. Missing physical measurements remain unavailable.

Physical measurements & uncertainties

Mean radius · km: 734.30 ±2.80 [1]
GM · km³/s²: 120.51511 ±0.00242 [SAT441]
Density · g/cm³: 1.0887 ±0.0125 [*]

Missions in the Saturn system · 5 records

5 launches · 0 linked events

These records cover the planetary system. A system mission did not necessarily visit this moon. Dedicated targets are marked separately; programme events include the journey and briefings. Launch outcomes do not establish arrival, landing success or present spacecraft operation.

Dedicated targets only

PLANETARY SYSTEM · UPCOMING