India, Aug. 21 -- How do you explore a place where the Sun never shines? China's space programme will soon embark on one of the most innovative lunar exploration missions in recent years.

We've known for nearly two decades that some form of water exists on the Moon. What we still don't know is exactly how much accessible water ice lies inside permanently shadowed craters, how deeply it is buried or what form it takes.

What we do know is that accessing that water ice will be a real challenge: it is found at the bottom of deep, hard-to-traverse craters where the Sun never shines, remaining untouched for billions of years at temperatures well below -200degC. These are among the most valuable places on the Moon, but the hardest to reach and...