What is the driest non-polar desert?

The Atacama Desert is the driest non-polar desert in the world.

Located along northern Chile's Pacific coast, the Atacama stretches for roughly 1,600 kilometres between the Andes and the Coastal Range. Its extraordinary dryness comes from several factors working together: the cold Humboldt Current, a persistent subtropical high-pressure system, and rain shadows formed by two mountain ranges.

Some parts of the desert receive only 1 to 2 millimetres of rain annually, while certain weather stations have recorded no rain for years. The Atacama is often called the driest place on Earth, but that wording can be misleading: Antarctica's McMurdo Dry Valleys are drier overall in some locations, which is why “non-polar” matters in this question.

The desert's Mars-like terrain has made it useful for testing instruments and procedures for future Mars missions. Despite its aridity, coastal fog called camanchaca supports lichens, algae, cacti and other specially adapted life.