BATTLE OF THE PLANETS

MARS

SCIENTISTS think that Mars (right), sometimes called the Red Planet, used to be like Earth. Billions of years ago, it may have had oceans and seas on its surface. At some point, its thick atmosphere was stripped away by the solar wind. All that’s left now is a dead, rocky world, coloured red by iron rusting on the ground. But there may still be water — and even life — beneath the surface.

URANUS

THE only planet in the solar system that rotates on its side, Uranus (left) is one of four gas giants in our solar system, meaning the planet is made almost entirely of helium and hydrogen. While most other planets spin in the direction in which they orbit, Uranus spins at 90 degrees to its orbit. This could be due to a large impact early in its life. Neptune, another gas giant, is particularly noticeable for its blue colour which is caused by a gas called methane in its atmosphere. We’ve only ever seen Neptune up close once, thanks to the Voyager 2 spacecraft in 1989.

JUPITER

A HUGE cyclone, the biggest storm in the solar system, has been raging on Jupiter for more than 400 years and is known as the Great Red Spot (right). At one point, it was bigger than Earth. The storm has been getting smaller in recent years but it is not thought to be calming down just yet. Gas giants such as Jupiter form when clouds of dust and gas draw together to make a larger object. The immense size of these produces the high pressure inside the planet. This results in liquids such as metallic hydrogen surrounding what’s thought to be a rocky core.