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Enceladus

Enceladus, one of the moons of Saturn Enceladus, one of Saturn’s moons, is a bright, silvery-white ball measuring only 498 kilometres (309 miles) across. Like a mirror, the surface of Enceladus reflects nearly all the light that reaches it. Part of its surface has craters but most other parts are smooth. The long grooves on Enceladus’s surface, some of them fringed by distinctive mint-green stripes, are thought to be faults (cracks) in the moon’s icy crust, possibly indicating the existence of a liquid layer lying beneath. The Cassini space probe made a series of flybys of Enceladus in 2015–17, sending back detailed images and information about the moon.



An artist's impression: the surface of Enceladus is coated by water ice erupted from ice volcanoes.

Eruptions of ice

There are craters and ridges in Enceladus's northern hemisphere, but its southern polar region is smooth. Astronomers think that Enceladus may be almost entirely coated by water ice. The ice has melted only recently, wiping out any craters from past meteorite bombardment. The surface is probably being regularly recoated by eruptions of ice bursting through cracks in the moon’s thin crust.
As Enceladus orbits Saturn, the planet's vast gravitational force pulls at the moon, keeping it in orbit. Every so often Dione, another, larger moon orbiting further out, aligns with Enceladus, pulling it towards itself. Astronomers think this repeated gravitational tug-of-war, which stretches and squeezes Enceladus in turn, is warming the moon's core and melting its icy exterior. 
Snaking across the smooth southern polar region of Enceladus are four long grooves, each fringed by a mint-green stripe. From these so-called “tiger stripes”, geyser-like ice "volcanoes" (known as cryovolcanoes) erupt fountains of water vapour and tiny hailstones 500 kilometres (300 miles) into space. The ice particles make up most of the material in Saturn’s E ring.
Grooves and mint-green stripes on the surface of Enceladus
Faults, wrinkles and "soft" craters on Enceladus's surface

Possible
existence of life

Enceladus was discovered by German-born British astronomer William Herschel, the discoverer of Uranus, in 1789. The find was made while he was using his new 1.2-metre telescope.

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