Mars is the 4th planet of the Solar System. Because of it's red, rusty colour, the ancients named it in honour of the god of war - Mars. The cause of such a colour of the planet is of course iron oxide which covers the planet's surface. On it there are many different landforms just like on Earth. Volcanoes, basins and deserts can be distinguished. Like on the Moon craters are numerous.
The heighest mountain of the Solar System - Olympus Mons - is located on Mars. It is an inactive volcano and rises up to 22 km above the mean planet surface. It's base is 550 km wide and it's crater has mean dimensions of: 85 km x 60 km. The volcano presumably last erupted about 10-20 mln years ago. Data comes from the Mars Global Surveyor probe.
The Solar System's largest canyon Valles Marineris is also located on Mars. It was discovered by the Mariner 9 probe. Marineris has a lengh of about 5000 km, width: 200km and depth: 7 km. The origin of this canyon is not yet know for sure. There are hypothesis that it came to form billions of years ago as a result of a rupture during the cooling stage of the planet.
Mars's poles just like Earth's are covered in ice. The polar ice cap has a diameter of about 1000 km and is covered with 3 km of ice. The ice is in fact dry ice - frozen carbon dioxide. The cap grows seasonally. In the winter when the temperatures drop to -150°C, CO2, which makes up around 95% of the atmosphere freezes on the surface. Only in summer does it sublimate and the size of the cap reduces.
The smooth plains area Vastitas Borealis is located on the northern hemisphere and outstretches around the ice cap; it spreads over 40% of the planet's surface. Presumably it is a relic of an immense impact to the planet.
