Today, Mars seems colder than the Arctic and drier than the Sahara.

Nevertheless, all our evidence so far indicates that Mars was a warmer planet in the past, with a thicker atmosphere and water that pooled on its surface, forming lakes and seas.

How did Mars lose its water? Did microbes appear on Mars, when the planet was more hospitable to life? The exploration of the red planet continues and eventually the first astronauts will walk on its surface.