The race to Mars is heating up with nations and private companies making long-term plans to land humans there – and even set up home.
There are several different scientific motivations. For some, it is the search for life or ancient signs of it. Others see it as a possible refuge for humanity should a future cataclysm occur here.
In addition to being our nearest neighbour, Mars is also the planet most like Earth: it once had water and a thicker atmosphere.
Bringing back samples, as Nasa hopes to eventually do, will give a clearer picture of what happened to the planet, and whether it could ultimately sustain human life.