Dnasa’s Mariner 9 probe made a revolutionary discovery in 1972. Surface images of Mars showed a network of dry, branched valleys. Some spanned more than a thousand kilometers. The American geologist Daniel Milton drew a remarkable conclusion from these observations the following year: “Many features on Mars are easiest to understand by the fact that there has been running surface water at some point in the past; running water is the only explanation for some of these characteristics. ”So were there huge, landscape-defining floods on our small, cold and dusty neighboring planet, whose atmospheric gases have largely escaped into space today? What might initially be difficult to imagine seems certain today: Mars once had a completely different climate than it does today. It was at least temporarily warm and humid – at least a time three and a half billion years ago when life arose on Earth.

With this knowledge, one of the central, but certainly the largest open question of Mars research was formed: Was or is there life on our neighboring planet too? It had an impact on all Mars missions in recent years and decades. The current Mars mission of the American space agency Nasa, which will start at the earliest this Thursday, should now provide decisive impulses for its answer: the Perseverance rover will look for evidence of past life – among other things by collecting rock and soil samples that will eventually be used for a comprehensive scientific analysis is to be brought back to Earth. This could finally provide the answers that missions on Mars themselves have so far been guilty of.

Today the conditions on the surface of Mars are not very life-friendly: The Hubble Space Telescope of our neighboring planet from August 26, 2003

The investigation will also have some relevance for the more general question of life in space. After all, as an earth-like rock planet near the outer edge of the “habitable zone” that allows liquid water, Mars is a planet that would be categorized as a promising candidate for a life-friendly environment if we were to observe it from a distance with our telescopes. His example can be used to study how physical and chemical development processes influence the habililty, the friendliness to life of a planet over time. The fact that large parts of its surface from the early phase of its history are preserved and accessible due to the lack of plate tectonics makes it particularly suitable for this. Numerous missions to Mars have given us a detailed, albeit sketchy, picture of the past of the Red Planet based on studies of its surface, atmosphere and physical fields.

Like the other planets, Mars was formed around four and a half billion years ago from dust that clumped into kilometer-sized chunks, so-called planetetesimals. These in turn grew into planetary embryos. After a few million years, Mars could have been largely formed in this way in order to form the core, mantle and crust relatively quickly. Magnetized rock in areas of the southern highlands indicates that Mars initially had a magnetic field generated by an internal dynamo, which disappeared around four billion years ago. At that time there was also widespread volcanism: gigantic volcanoes such as Olympus Mons, around 25 kilometers high, testify to this, and it seems that it last erupted less than a hundred million years ago.