PHOBOS is a name you are going to hear a lot in the coming years. It may be little more than an asteroid – just two-billionths of the mass of our planet, with no atmosphere and hardly any gravity – yet the largest of Mars’s two moons is poised to become our next outpost in space, our second home.
Although our own moon is enticingly close, its gravity means that relatively large rockets are needed to get astronauts to and from the surface. The same goes for Mars, making it expensive to launch missions there too