Ariel

Moon· orbits Uranus

Ariel is the brightest of Uranus's moons, its icy surface cut by a network of fault valleys (chasmata) that suggest past geological activity.

Open in 3D viewSee Ariel in the live, interactive 3D map

Key facts

Mass

1.25 × 10²¹ kg

0.017 Moon masses

Radius

579 km

33% of our Moon's radius

Surface gravity

0.249 m/s²

3% of Earth's gravity

Day length

2.5 days

Orbit around Uranus

2.52 Earth days

Science

Physical

Mass: 1.25 × 10²¹ kg · 0.017 Moon masses; JPL / IAU mean radii; spacecraft-tracked GM where measured
Radius: 579 km · 33% of our Moon's radius; JPL / IAU mean radii; spacecraft-tracked GM where measured
Density: 1,539 kg/m³ · 1.5× water; Computed from mass and radius
Surface gravity: 0.249 m/s² · 3% of Earth's gravity; Computed from mass and radius
Escape velocity: 537 m/s · 5% of Earth's escape velocity; Computed from mass and radius

Orbit around Uranus

Distance from Uranus: 190,929 km; From JPL orbital elements
Orbital period: 2.5 days; From JPL orbital elements
Eccentricity: 0.001; From JPL orbital elements
Inclination to the J2000 equator: 0.00 °; From JPL orbital elements

Rotation

Rotation period: 2.5 days
Tidal locking: Tidally locked to its parent

Temperature

Mean: 60 K (-213 °C)

Composition

Bulk composition: Roughly equal water ice and silicate rock, with possible carbon-dioxide ice.

Radiation & temperature

Insolation: 0.00265 S⊕ · 1/378 of the sunlight Earth receives; Computed from the distance to the Sun (inverse-square; Earth's sunlight = 1), before any atmosphere.
Bond albedo: 0.53 · reflects 53% of incoming sunlight
Equilibrium temperature: 52 K (-221 °C); Computed from albedo + distance from the Sun (airless black body)
Measured mean temperature: 60 K (-213 °C)
Greenhouse warming: +8 K; Measured temperature minus the airless equilibrium — the greenhouse effect

Discovery & history

Discovered: October 24, 1851
By: William Lassell
Method: Visual discovery (telescopic)
Name: Ariel, an airy spirit in Shakespeare's 'The Tempest' and Pope's 'The Rape of the Lock'.

William Lassell discovered Ariel in 1851. The brightest of Uranus's moons, it also has the youngest surface, criss-crossed by fault canyons whose floors appear to have been flooded by icy flows.