Biggest moons in the Solar System, in order of size

Ganymede, Jupiter's largest moon, is the biggest moon in the Solar System and wider than the planet Mercury. Saturn's Titan comes second, and our own Moon is fifth.

See moons in 3D, at true scale

Moons

Ganymede

Ganymede is the largest moon in the Solar System — bigger than Mercury — and the only one with a magnetic field of its own, generated by a molten iron core.

Titan

Titan is the only moon with a thick atmosphere, and the only world besides Earth with liquid on its surface — though its rivers, lakes and rain are methane and ethane, not water.

Callisto

Callisto is the most heavily cratered object in the Solar System — a surface so old and so unchanged that it records four billion years of impacts.

Io

Io is squeezed between Jupiter's gravity and the pull of the other large moons, and the friction melts its insides.

The Moon

The Moon formed when a Mars-sized body struck the young Earth and the debris pulled itself together in orbit.

Europa

Beneath Europa's cracked shell of ice lies an ocean holding perhaps twice as much water as every ocean on Earth combined.

Triton

Triton orbits Neptune backwards, which almost certainly means it did not form there: it is a captured object from the Kuiper Belt, seized by Neptune's gravity.

Titania

Titania is the largest moon of Uranus, a world of ice and rock split by enormous canyons that may have cracked open as its interior froze and expanded.

Rhea

Rhea is Saturn's second-largest moon, a heavily cratered ball of ice with a little rock.

Oberon

Oberon is the outermost of Uranus's large moons, an old, cratered world of ice and rock.

Iapetus

Iapetus is Saturn's two-faced moon: its leading side is as dark as coal and its trailing side as bright as snow.

Charon

Charon is half the width of Pluto, so the two do not simply orbit one another: they both circle a point in empty space between them, always showing each other the same face.

Dione

Dione is an icy moon of Saturn with bright ice cliffs streaking its trailing side.

Tethys

Tethys is a mid-sized moon of Saturn made almost entirely of water ice.

Enceladus

Enceladus hides a global ocean of salty water beneath an icy shell.

Miranda

Miranda is the smallest of Uranus's five large moons and one of the strangest-looking worlds known: a patchwork of grooved terrain, giant cliffs and smooth plains, as if it had been shattered and pieced back together.

Mimas

Mimas is the smallest body in the Solar System still rounded by its own gravity.

Phobos

Phobos is the larger moon of Mars and orbits closer to its planet than any other moon in the Solar System, only 6,000 km above the surface.

Deimos

Deimos is the smaller and outer of the two moons of Mars, a lumpy, dusty body barely 12 km across.

Sizes by category

• How big is the universe?
• The Solar System to scale
• Eclipses
• Meteor showers
• When to see the planets
• Space simulations
• Planets
• Dwarf planets
• Asteroids & comets
• Exoplanets
• Stars
• Black holes
• Nebulae & clusters
• Galaxies
• Cosmic structures