Titania

Titania is Uranus's largest moon and the eighth-largest in the solar system. Its surface is a mixture of cratered terrain and large canyon systems — Messina Chasma, the moon's longest, runs 1,500 km. The surface is less heavily cratered than expected, suggesting geologically recent resurfacing. A tenuous carbon-dioxide atmosphere was tentatively detected via stellar occultation, making Titania a possible host for trace volatile chemistry. Like all the major Uranian moons, our knowledge of Titania comes almost entirely from a single Voyager 2 flyby in 1986.

Titania is roughly equal parts water ice and rock by mass. Models suggest a differentiated interior with a rocky core, possibly a subsurface liquid ocean during its early history, and an icy mantle. The low density of impact craters on parts of the surface implies cryovolcanic resurfacing within the past few billion years.

Voyager 2's 1986 flyby returned hemisphere-scale imaging — the southern hemisphere only, since Uranus's extreme axial tilt put the northern hemisphere in darkness. Hubble and ground-based occultations have refined estimates of Titania's atmosphere and surface composition, but no follow-up mission has visited.