Short answers, pulled from the story.
The Antarctic Desert is the largest desert in the world, covering 5,482,651 square kilometers of ice and rock. It receives less precipitation than the Sahara but is defined by its extreme cold rather than heat.
Desert plants conserve water by adopting crassulacean acid metabolism to open stomata at night, reducing leaf size, or abandoning leaves altogether. Cacti store water in modified trunks and absorb rain rapidly through shallow roots to survive months or years without precipitation.
The Tuareg traded across the Sahara between the 8th and 18th centuries, transporting slaves, ivory, and gold northwards and salt southwards. Several million slaves may have been taken northwards across the Sahara during this period.
The White Sands National Park is located in New Mexico, featuring vast white dune fields formed by gypsum crystals eroded from nearby limestone mountains. These crystals resemble snow-covered landscapes and are deposited by wind in level areas.
Desert animals remain underground during the day to avoid extreme heat and conserve water through reduced skin and respiratory loss. Burrows at depths of more than 1.5 meters maintain temperatures between 20 and 30 degrees Celsius regardless of external conditions.
A large saguaro cactus can hold eight tons of water after a good downpour due to its concertina-like trunk surface that allows expansion. These cacti grow slowly and may live for up to two hundred years in the Sonoran Desert.