A desert is defined as an area where less than 19.6 inches (50 centimeters) of rain falls each year. Deserts cover about one third of the Earth's land surface. Examples of famous deserts include the Sahara, Atacama and Mojave deserts. Deserts aren't just hot and dry places, though; like Antarctica, they can also be cold and dry. Read below for news about these driest spots on Earth.