Antarctica. Parts of the continent have seen no rain for two million years.
A desert is technically defined as a place that receives less than 254 mm (10 inches) of rain a year.
The Sahara gets just 25 mm (1 inch) of rain a year.
Antarctica’s average annual rainfall is about the same, but 2 per cent of it, known as the Dry
Valleys, is free of ice and snow and it never rains there at all.
The next-driest place in the world is the Atacama Desert in Chile. In some areas, no rain has fallen
there for 400 years and its average annual rainfall is a tiny 0.1 mm (0.004 inches). Taken as a whole,
this makes it the world’s driest desert, 250 times as dry as the Sahara.
As well as the driest place on earth, Antarctica can also claim to be the wettest and the windiest.
Seventy per cent of the world’s fresh water is found there in the form of ice, and its wind speeds are
the fastest ever recorded.
The unique conditions in the Dry Valleys of Antarctica are caused by so-called katabatic winds
(from the Greek word for ‘going down’). These occur when cold, dense air is pulled downhill simply
by the force of gravity. The winds can reach speeds of 320 kph (200 mph) evaporating all moisture –
water, ice and snow – in the process.
Though Antarctica is a desert, these completely dry parts of it are called, somewhat ironically,
oases. They are so similar to conditions on Mars that NASA used them to test the Viking mission.
STEPHEN The Dry Valleys, in Antarctica, are free from ice and snow, and haven’t seen
rain for two million years. So it’s a long way clear of its closest contender, the
Atacama, parts of which haven’t recorded rain for a mere 400 years. The Sahara is
lush by comparison.
STEPHEN ‘Lush’ is often shouted at you, I know. I’m going to shout it again.