DK - WOW! The Visual Encyclopedia of Everything

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THE MOON

The Moon is Earth’s only natural satellite. It is about a quarter the size of Earth and the fifth largest of all moons. The surface of this dry ball

of rock is covered in impact craters.^2

IO

Colourful Io is the most volcanic moon in the Solar System. Its surface is constantly being renewed as molten rock erupts through its thin silicate-rock crust, and fast-moving columns of cold gas and frost grains shoot up from surface cracks.^3

EUROPA

The smallest of Jupiter’s four major moons, Europa has an icy surface criss-crossed with networks of brownish grooves. The crust slowly drifts around on top of a deep ocean of liquid water that might be home to alien life.^4

GANYMEDE

At 5,262 km (3,267 miles) across, Ganymede is the largest moon in

the Solar System and belongs to the largest family of moons – the moons of Jupiter. Astronomers know of

79, but the number is likely to rise

as smaller moons are detected. Ganymede is made of rock and

ice with an icy crust.

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TITAN

Titan is the largest of Saturn’s 62 moons. On its surface are bright highlands, dark plains, and methane lakes and seas. It is the only moon with a substantial atmosphere, which is rich in nitrogen and extends out for hundreds of kilometres.^6

TITANIA

Titania is the largest of the 27 moons orbiting Uranus. Titania and the planet’s other major moons, Oberon, Umbriel, Ariel, and Miranda, are named after characters in English literature. Impact craters and large cracks are seen on its grey, icy surface.^7

IAPETUS

Iapetus is a moon of contrasts. Most

of its crater-covered terrain is bright and icy, but the rest appears to be coated by a dark material. It is one

of Saturn’s seven major moons, along with Titan, Rhea, Dione, Tethys, Enceladus, and Mimas.

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TRITON

Triton is by far the largest of Neptune’s 14 moons, a rock-and-ice ball with a young, icy surface. It is nicknamed the cantaloupe as its linear grooves, ridges, and depressions resemble a melon’s skin.^9

SMALL MOONS

Most moons are less than 400 km (250 miles) across and irregular in shape, like Saturn’s Epimetheus and Hyperion. Many of these smaller moons, like Mars’s two moons Phobos and Deimos, may have started off

as asteroids or comets.

Neptune’s only large moon

probably began life as a

dwarf planet before being

captured by Neptune’s gravity

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