Ariel (moon) — an icy, geologically varied satellite of Uranus

Discovery and name

Ariel was discovered on October 24, 1851 by the British astronomer William Lassell. The discovery occurred at the same time as that of the moon Umbriel; both were reported shortly after observation. The name "Ariel" was chosen from literature: it appears as a sylph in Alexander Pope’s poem and as the airy spirit who serves Prospero in Shakespeare’s play. For contemporary references see discoverer, Pope and Shakespeare; the companion moon is noted at Umbriel.

Physical characteristics

Ariel is a mid-sized icy moon with a roughly spherical shape. Its bulk is a mixture of water ice and denser rock. The surface presents a contrast between heavily cratered terrains and smoother, grooved or canyoned regions. Scientists interpret these contrasts as evidence that parts of Ariel’s outer shell were reshaped after the period of heavy bombardment.

Surface and geology

Imagery from the Voyager 2 flyby in 1986 provided most of what is known about Ariel’s geology. The camera revealed extensive networks of fault scarps, troughs and canyons, as well as plains that may be younger and less cratered. These features suggest tectonic deformation and possibly cryovolcanic resurfacing in the past, driven by internal heat or tidal effects early in the moon’s history.

Orbit, origin and significance

Ariel orbits Uranus among several other principal satellites and is tidally locked, showing the same face to the planet. Its formation is thought to have taken place in the circumplanetary disk that surrounded Uranus during its early evolution. Ariel is important to planetary science because its mixed geology offers clues about how small icy worlds can retain or release internal heat and how that affects surface renewal.

Key characteristics

• Composition: primarily water ice with rock and darker materials.
• Surface: a mixture of old, cratered regions and younger tectonic or smooth plains.
• Exploration: most knowledge comes from Voyager 2 observations.
• Cultural: named for literary spirits from both Pope and Shakespeare.