Ariel

Click image for description
Discovery
Discovered by	William Lassell
Discovered in	1851
Orbital characteristics
Mean radius	190,900 km
Perihelion
Aphelion
Eccentricity
Orbital period	2.52 days
Inclination	°
Satellite of	Uranus
Physical characteristics
Mean diameter	1157.8 km
Surface area	4,200,000 km2
Mass	1.35×1021kg
Mean density	1.67 g/cm3
Surface gravity	m/s2
Escape velocity	km/s
Rotation period	2.52 days
Axial tilt	°
Albedo
Surface temperature	min mean max  ? K  ? K  ? K
Atmospheric pressure	0 kPa

Ariel (air'-ee-el) is a moon of Uranus discovered on 1851-10-24 by William Lassell. It was discovered at the same time as Umbriel.

Name

Ariel is named after the leading sylph in Alexander Pope's poem Rape of the Lock.

The name "Ariel" and the names of all four satellites of Uranus then known were suggested by John Herschel in 1852 at the request of Lassell ([1]). Lassell had earlier endorsed Herschel's 1847 naming scheme for the seven then-known satellites of Saturn and had named his newly-discovered eighth satellite Hyperion in accordance with Herschel's naming scheme in 1848.

It is also designated Uranus I.

Physical characteristics

The first and so far only close-up observations of Ariel were made by the Voyager 2 probe during its January 1986 Uranus fly-by. Because the moon's south pole was pointed towards the Sun, only the southern hemisphere was photographed.

Ariel's composition is roughly 50% water ice, 30% silicate rock, and 20% methane ice, and it appears to have regions of fresh frost in places. Largely devoid of impact craters, Ariel appears to have undergone a period of intense geological activity that has produced a huge network of fault canyons and liquid water outflows over its surface.

Scientists recognise the following geological features on Ariel:

• Craters
• Chasmata (chasms)
• Valles (valleys)

See also

• List of geological features on Ariel

External links

• William Lassell, Astronomical Journal 2 (1851) 70
• AN, 33 (1852) 257/258
• AN, 34 (1852) 325/326