A spacecraft has launched from Japan headed for Mars' moon Phobos, where it will attempt to grab some moondust and bring it back to Earth. If it is successful, this will become the first time a sample has been returned from Mars or its moons to be analysed in laboratories here on Earth.
It is hoped that the Mars Moons Exploration (MMX) mission, which is led by the Japanese Space Agency, will solve the mystery of how Mars's moons formed. Prof Sara Russell, from the Natural History Museum, who is the MMX mission's deputy for sample analysis, said: "There hasn't yet been a successful mission to go to Phobos and bring a bit back to Earth. "I think this is an incredibly ambitious and fun mission," she said.
There are only three moons in the inner Solar System: our own Moon, and two around Mars, which are called Phobos and Deimos. Both of these are tiny – Phobos is about 20km (12 miles) across and Deimos is about 10km (six miles) across. They are also irregularly shaped, looking a bit like space potatoes. The MMX spacecraft will study Deimos as it arrives in the Mars neighbourhood, and then will focus on Phobos.
It plans to set down a small rover to explore the terrain, though this will be no easy feat. Sara Russell says no one has ever landed a rover on such a small moon. "The moon itself doesn't have very much of its own gravity," she explained.
"But it's next to an enormous planet that's got a much higher gravity, and that makes it much harder to get a rover onto the surface." Mars got its moons about 4.5bn years ago – but no one knows how they formed