Crashing a rocket to look for water

NASA steered a spent Centaur stage into a crater at the Moon's south pole that has not seen sunlight for two billion years, and flew a second spacecraft through the plume to taste it.

The plume contained water — several per cent of the ejected mass — along with ammonia, methane and mercury. It settled a century of argument: the Moon is bone dry everywhere the Sun reaches, and there is ice in the places it never does.