Dione

Dione

Discovery
Discovered by	Giovanni Domenico Cassini
Orbital characteristics
Semi-major axis	377,400 km
Eccentricity	0.0022
Orbital period (sidereal)	2.736915 days
Average orbital speed	10.03 km/s
Known satellites	Helene, Polydeuces
Physical characteristics
Dimensions	1122.8 × 1122.8 × 1122.8 km
Mean radius	561.4 km
Surface area	3,959,000 km²
Volume	741,000,000 km³
Mass	1.09552 × 10^21 kg
Mean density	1.478 g/cm³
Surface gravity	0.232 m/s²
Escape velocity	0.515 km/s
Synodic rotation period	synchronous
Axial tilt	zero
Albedo	0.998
Temperature	87 K

Dione is a natural satellite of Saturn. It was discovered by the Italian astronomer Giovanni Domenico Cassini in 1684. Dione is the fifteenth-largest moon in the Solar System and the fourth-largest moon of Saturn.

Physical characteristics

Dione has a mean radius of 561.4 km and a mass of 1.09552 × 10^21 kg. Its density is 1.478 g/cm³, which suggests that it is composed of a mixture of water ice and silicate rock. The surface of Dione is heavily cratered, with a number of bright ice cliffs and fractures.

Orbit and rotation

Dione orbits Saturn at a distance of approximately 377,400 km. It has a very low orbital eccentricity of 0.0022 and completes one orbit around Saturn in about 2.736915 days. Dione is in synchronous rotation with Saturn, meaning that it always shows the same face to the planet.

Surface features

The surface of Dione is marked by a variety of geological features, including craters, chasms, and ice cliffs. The most prominent feature is the Janiculum Dorsa, a large ridge that stretches across the moon's surface. Other notable features include the Carrel Crater and the Padua Chasmata.

Subsatellites

Dione has two known trojan moons, Helene and Polydeuces, which share its orbit around Saturn.

Exploration

Dione has been studied by several spacecraft, including the Voyager missions and the Cassini spacecraft. These missions have provided detailed images and data about Dione's surface and composition.

See also

• List of natural satellites
• Moons of Saturn
• Giovanni Domenico Cassini
• Voyager program
• Cassini–Huygens

Related pages

• Saturn (planet)
• Helene (moon)
• Polydeuces (moon)
• Voyager program
• Cassini–Huygens