Mars

Mars is Earth's outer neighbour and the fourth and last terrestrial (rocky) planet in the Solar System. Its red colouring is particularly striking, allowing it to be clearly distinguished with the human eye from the whitish stars in the firmament. The red colour could be attributed to the abundant iron oxide (rust) on the surface of Mars.

The first close-up photos of the planet were taken by the Mariner 4 probe in 1965. Later, other probes were able to produce a more detailed map of the surface of Mars, and the Viking 1 and 2 probes that landed on the planet in the 1970s provided the first close-up images of their landing sites. The surface of Mars is a dusty landscape strewn with boulders. Violent dust storms sweep across the entire planet from time to time.

The southern and northern hemispheres of Mars differ considerably, with many craters in the southern hemisphere being evidence of an ancient surface, while the northern hemisphere appears geologically younger and free of craters. Mars is home to some huge volcanoes, including Olympus Mons which, at a height exceeding 20,000 metres, is the highest mountain in the Solar System. Mars is the record holder in the Solar System not only in terms of altitude, but also when it comes to depth, as its deepest canyon, the Valles Marineris, reaches depths of over 6000 metres in places and is a gigantic tectonic fracture in the surface of Mars.

It is assumed that the Martian atmosphere was once denser, but became less so over time due to the low gravity of Mars. The present thin atmosphere creates low pressure and low temperatures, so water cannot exist in liquid form on the planet today. However, there is some evidence to suggest that liquid water was once present on Mars. On the one hand, the existing polar ice caps, which grow and shrink seasonally, contain water ice in addition to carbon dioxide ice. There are also old dry riverbeds on the surface of Mars.