For a real, working Moonbase, we will have to develop new rockets and landing craft. That technology will be very useful for the next outward step: all the way to the planet Mars. Right from the beginning of the space age, Mars has fascinated scientists and engineers. The early Mars probes, launched back in the 1960s and 1970s, were great achievements, but they brought back disappointing news for all those who hoped that Earth's neighbour planet might support life. The place is very cold – never warmer than 15 degrees, even at its midsummer equator, and in the winter night temperatures fall to around -130°. Its atmosphere is almost 95% carbon dioxide, and far too thin even to protect the surface from ultra-violet radiation from the Sun.

Martian landscape

But

The ExoMars rover will explore the Martian surface

later probes have brought back better news. Spacecraft photographs – the entire planet has been mapped from orbit – show that water once flowed on the arid Martian surface. Clearly, Mars was once much warmer. Even if the planet bears no life today, it may have done so in its youth. Possible fossil bacteria have already been found in a meteorite of Martian origin: there may be plenty more waiting for us on Mars itself. And not just fossils: some at least of the planet's lost water may still be there, lying beneath the Martian surface. If so, there is a good chance that Martian life may have gone underground with it: there are certainly bacteria on Earth that could live happily under such conditions.

In fact, the search for extraterrestrial life is a major reason for further exploration. Life beyond the Earth could well be the most exciting scientific discovery of all time. It is probably out there somewhere: after all, the Universe is a big place. There are at least 100 billion stars in our own galaxy, and perhaps as many galaxies scattered throughout deep space. Until quite recently, though, astrobiologists (scientists studying extraterrestrial life) were not optimistic about life in our own Solar System – beyond the Earth, that is. But in the last few years, new discoveries both on Earth and in space have changed things dramatically.