Earth is a very special planet. It is the only celestial body in the solar system on which we know life exists. Could there be life on other planets or moons? Mars is always the first mentioned in this context; it has many properties in common with Earth, and in its geological past water also flowed over its surface. Today, however, conditions on Mars are so extreme that it is hard to imagine that organisms like those found on Earth could survive on that cold and arid desert planet. One of the aims of the DLR-coordinated experiment BIOMEX (BIOlogy and Mars EXperiment) on the International Space Station (ISS) was to find out if this is indeed possible. The results are now available.