The Solar System

The Solar System

Crash and splash

Astronomers now believe the Moon is the remains of a giant cosmic traffic accident. In its very early days, the Earth was hit by a runaway planet the size of Mars. White-hot molten rock were splashed into space, and solidified into a ring of rocks around the Earth. These then came together to make up the moon.

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A D V E R T I S E M E N T

Ice on the moon

Circling over the moon�s poles in 1998, the American Lunar Prospector spacecraft discovered patches of ice within some deep craters, where it is always shaded from the Sun, so the ice never melts or evaporates. Future manned expeditions could melt the ice into water, for drinking, washing and turning into rocket-fuel: there is enough ice to make a lake 10km across and 10m deep.

Earth

If you approached the Solar System from space, one planet would stand out as very odd. The third world from the sun is brightly coloured, in shades of mainly blue, with patches of red and green, and constantly shifting patterns of white cloud. And it has an unusually large moon; which-by contrast- is dull and uniformly brown.

The perfect planet

Come closer, and you find blue is liquid water. This is the only rocky planet with water. Test the atmosphere, and again this planet is unique: the air contains a lot of reactive gas oxygen. And finally, take a closer look at the green areas. Here there is ample vegetation and animal life. This is the only planet in the solar system obviously inhabited life forms.

The earth is special mainly because it is located at the perfect distance from the sun. The temperature here is just right for water to exist as a liquid: get in as close Venus and the water just boils away as steam, while as far out as the orbit of Mars water is frozen to ice.