Think of a desert planet and you might think of sand dunes that go on forever and, perhaps, sandworms (particularly if you’ve read Dune).
Traveller defines a desert planet as having a Hydrographic Percentage of zero. This means that there is no free standing water – there may be ice caps, and there may be aquifers, but there are no rivers, lakes, or seas.
Sounds pretty deserty to me.
Consider this: In the centre of the North Island of New Zealand, three volcanoes have formed a high plateau. The soil is a mixture of volcanic pumice and sand and is very porous. It is a bleak, cold, windswept place, and very dry. It is known as the Desert Plateau and is an example of a cold desert.
In fact, the driest place on earth is the Dry Valley region of Antarctica, not exactly known for its tropical climate, where it has not rained for 2 million years. The Atacama Desert in Peru is more likely to experience snow than rain – it hasn’t rained in 400 years. Parts of Eastern Iran, Afghanistan, and a swath of territory extending north and east across what were the Southern States of the old USSR are cold and dry – this, after all, is the homeland of the famous two-humped Bactrian camel.
Hot deserts and cold deserts.
Having established the criteria for a Desert Planet, then our nearest one is Mars where you have the worst of all climatic combinations – no free standing water; cold; and dust to clog all your vital equipment. Mars even has ice caps.
Why would anyone chose to live on a Desert Planet?
Ever since Percival Lowell dreamed of canals on Mars, the story of a doomed race clinging to a dying world has resonated through Science Fiction, especially in the planetary romances of the 20s and 30s.
"I can see you, John Carter!"
With modern theories of climate change and the fossil record of Earth, we can see how periods of hot dry and cold dry have shaped the world we live in, and offer a more meaningful reason than the poetic “dying world” for a desert planet.
People might move to a desert world in search of natural resources, either in the shifting sands, or buried beneath them, or produced by life forms adapted to the environment – the Spice mélange produced by the Sandworms of Arrakis in Frank Herbert’s Dune novels brings the Spacing Guild and Imperial Forces to the planet Arrakis, which upsets the Fremen already resident there.
A desert planet might be seen as a place of refuge or a place of testing, or even both – the Fremen certainly considered Arrakis as a testing ground, while it hid them from those that oppressed them – stripping away the conceits of civilisation and bringing the people into a state of awareness of themselves and their environment.
For the Adventurer, the desert planet will test fortitude and resourcefulness as they strive to either find what has brought them there, or rescue themselves from the environment. Desert Worlds often conceal secret bases, lost cities or abandoned Ancients sites where fabulous technology or treasures may be found. I have a pirate base on the desert planet Golus in my Traveller campaign; there’s a Forerunner site and pirate base on the desert world orbiting a red dwarf star in Night of Masks by Andre Norton; and there are desert tribes and gangster/pirate bases in the deserts of Tatooine in Star Wars and Return of the Jedi.
Desert Worlds are extreme worlds, and they can be both incredibly interesting backdrops, as well as characters in their own right, in the stories you may want to tell.