A desert was a dry area of a planet that had very few sources of water. There were whole planets that were deserts, such as Aridius (TV: The Chase) and San Helios after it was ravaged by the Swarm. (TV: Planet of the Dead)
Sontar sand shrews inhabited the deserts on Sontar. (PROSE: The Sontaran Games)
Gethria was a largely desert planet. (PROSE: The Dalek Generation)
