The planet Mars: perfect if you like freezing dust clouds of tremendous intensity but dislike oxygen and gravity.

The planet Mars is the fourth planet from the Sun and there has been much speculation over the years about the possibility of other life forms existing there. From the Earth, Mars is easily seen in the night sky as a red star-like object that moves through the sky with a period of just over two years.

Through the looking glass

Seen through a telescope Mars appears as a small reddish disk on whose surface dark markings can (with difficulty) be seen. Also visible is one or other of its polar caps. Even with large telescopes it is very difficult to see detail and many experienced observers were deceived into thinking that they had glimpsed features, such as the infamous canals, that in fact were not there.

Almost all that we know about the surface of Mars and its atmosphere was discovered by the various space probes that have orbited the planet and landed on its surface.

What’s the atmosphere like?

We know that the atmosphere of Mars has a pressure less than one hundredth of the Earth's and that it is composed mainly of carbon dioxide with a little nitrogen and argon; there is almost no oxygen. There is a small amount of water vapour which condenses in some places to give thin clouds and fog. There are polar caps at each pole which grow in the Martian winters, with the addition of deposits of solid carbon dioxide, and decrease in the Martian summers to leave what is thought to be a small residue of ordinary water ice.

A chill in the ‘air’

The surface of Mars shows impact craters, like the Moon, mountains, rift valleys, ridges, hills plains and extinct volcanoes. There are signs that water existed on the surface at some earlier stage of the planet. Winds can be very severe and are responsible for extensive weathering of the rocks on the surface. Sometimes the winds blow up enormous sandstorms that obscure the view of the planet's surface. The surface temperatures on Mars can rise to about 0°C in the summer but fall to near -100°C before sunrise.

Earth 2.0?

The planet Mars rotates in 24 hours and 37 minutes about an axis tilted by 24° to its orbital plane. Although it is only 6794 km in diameter it is probably the most Earthlike of all the planets. There are some suggestions that it might be possible to alter the planet's atmosphere sufficiently to enable a permanent base to be set up there. Until that is done Mars will represent a very hostile environment for any human visitor.

Little moons

The planet Mars has two moons, Phobos and Deimos. They are both very small, being less than 30 km across. It is likely that they were both asteroids that were captured by Mars. Phobos is very close to Mars and its orbital period is less than the rotational period of Mars. It thus would be seen to rise in the west and set in the east. Deimos is further away from Mars and would be seen to behave more conventionally.

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