Mars is the fourth planet from the sun and one of Earth's nearest neighbors. It is also the only other planet in the solar system where humans may one day live. Mars is smaller and colder than Earth, but is otherwise remarkably similar. It has days and seasons, a thin atmosphere and, quite possibly, significant reserves of water buried as ice beneath the surface. there is even a chance that Mars once played a host to simple life forms, and that fossilized remains of long extinct creatures are buried there.

In 1984, scientists discovered a meteorite in Antarctica which they believe came from Mars. Inside the four-pound rock were traces of what may be the fossilized remains of primitive, single-celled organisms, suggesting that there was once life on Mars.

The most likely future for Mars from a human point of view is a mining colony, supplying us with minerals that have been exhausted on earth. Mars is rich in minerals - especially iron and aluminum, which even in the 24th century, will still be the basis of engineering and construction. Other elements required could be shipped from other sources such as Mercury or the Asteroid Belt.

Of all the planets in the solar system, Mars is almost certainly the most like ours. Its axis is tilted like the Earth's, which gives it seasons. Mars has a relatively warm summer, when temperatures in the southern hemisphere can reach 68 degrees F, but a long cold winter that sees them plunge to -284 degrees F.

Over 4 billion years ago, Mars was covered with massive volcanoes - just like the Earth - and possibly had some surface water, which gathered in flash floods, carving water channels into the surface. Like the Earth, Mars has a cloudy atmosphere; although the Martian "air" is much thinner, and the wispy clouds are made of carbon dioxide rather than water vapor.

So, despite its many similarities to Earth, Mars is a far from hospitable place. If you had landed there without a space suit, not only would you suffocate but, due to the much lower atmospheric pressure, your blood would boil within minutes.

Apart from the lack of oxygen and low atmospheric pressure, you would have to withstand the continuous winds that blow across the Martian surface at speeds of over 125 miles per hour, whipping up giant clouds of fine orange-brown dust in their wake. Its is the dust that has earned Mars the nickname "The Red Planet", although "Rust Planet" might be more appropriate, since the color is explained by the big proportion of iron in the planet's rocks - on average, almost twice as much as on Earth. Mars is also very dry and cold. Even on a warm summer's day the ground rarely get above freezing point, and on a winter mornings the rocks are often coated with a fine layer of carbon dioxide "frost".

The two tiny moons of Mars, Phobos and Deimos, race around the planet in about 8 hours and 30 hours respectively. They are thought to be asteroids that strayed too close to the planet in the distant past and were captured by its gravity. If Phobos, the closer of the two, maintains its present orbit, it is likely to crash into Mars in about 100,000 years' time. there is also some evidence to suggest that the planet has suffered similar collisions in the past.