Rhea (moon)

Rhea (/ˈriːə/;^[a] Ancient Greek: Ῥέᾱ) is Saturn's second largest moon. It is made of ice and rock.

Rhea

Cassini view of Rhea's anti-Saturnian hemisphere, showing the moon's two largest impact basins (Mamaldi above and left of center, and adjacent Tirawa to its upper right). At highest resolution, several long linear features are visible: halfway down from center is Harahvaiti Fossa, while near the limb left of the bottom is Koykamou Catena.
Discovery
Discovered by	G. D. Cassini
Discovery date	December 23, 1672
Designations
Alternative names	Saturn V
Adjectives	Rhean
Orbital characteristics [1]
Semi-major axis	527 108 km
Eccentricity	0.001 258 3
Orbital period	4.518 212 d
Inclination	0.345° (to Saturn's equator)
Satellite of	Saturn
Physical characteristics
Dimensions	1532.4×1525.6×1524.4 km
Mean radius	763.8 ± 1.0 km
Surface area	7 337 000 km²
Mass	(2.306 518 ± 0.000 353)×1021 kg (~3.9×10−4 Earths)
Mean density	1.236 ± 0.005 g/cm³
Surface gravity	0.265 m/s²
Escape velocity	0.635 km/s
Rotation period	4.518 212 d (synchronous)
Axial tilt	zero
Albedo	0.949 ± 0.003 (geometric)
Surface temp. min mean max Kelvin 53 K   99 K
Apparent magnitude	10 [2]

Photo of Rhea taken by the Cassini-Huygens probe

Ring system

Main article: Rings of Rhea

Rhea may have a thin ring system with three narrow bands in a disk of solid particles. These would be the first rings seen around a moon. The discovery was announced in the journal Science on March 6, 2008.

Notes

1. In US dictionary transcription, US dict: rē′·ə.