The answer may be that virtually all the water on Mars is now locked in the permafrost layer under the surface, with more contained in the planet's polar caps.

A Bedfordshire mother reported that her son was "easy" : a day locked in his bedroom with bread and water was enough to curb naughtiness.

Although we live on a water-covered planet, only 1% of the world's water is available for human use, the rest locked away in oceans, ice, and the atmosphere.