Why Do All the Planets Look Different?

The reason each of the planets looks different to us is that each one seems to be made up of different substances. Even though they are all planets revolving around the sun and part of the solar system, their composition varies.

We actually know very little about what the planets are made of, and this is one of the questions man hopes to answer with the space explorations that have taken place and those that are being planned for the future.

Let's take a brief look at each of the other planets and see what is known of their make-up. Mercury is a small, rocky world. It has some dark areas and many craters on its surface, but has no atmosphere or water of any kind.

Venus is a white globe with some hazy markings. It is completely covered by a layer of white clouds, which are not made of water vapour but of concentrated sulphuric acid. Underneath its clouds, Venus's atmosphere is made largely of unbreathable carbon-dioxide gas. This traps heat from the sun like a blanket, so temperatures at the planet's surface reach nearly 500°C, and there is scarcely any water on Venus.

Mars is known as the red planet because of the colour of its deserts. It is half the size of earth and has a thin atmosphere of carbon-dioxide in which clouds form. No definite signs of life have been found on Mars, perhaps because it is very cold there.

Jupiter appears as a yellowish globe with colourful bands of clouds swirling around it and a giant red spot clearly visible in the clouds. It is agiant ball of liquid, mostly hydrogen and helium, becoming denser and denser towards the planet's centre.

Saturn is mostly liquid hydrogen with a set of brilliant rings around it. These are made of countless particles all moving in orbits around the planet like miniature moons.Uranus has rings around it too, though these are much darker than Saturn's. Neptune is a dim greenish object, and Pluto is the smallest planet in the solar system, smaller even than our own moon. It has an eccentric orbit that sometimes brings it closer to the sun than Neptune.

Exploration of space by satellites and probes is helping scientists learn more about the other members of the solar system.