Need help creating a sci-fi world: Calling all geologists and planetologists!

I've been working on a sci-fi campaign for some time. The campaign is set on a desert planet after a total planetary war. Temperatures often get up to 110 degrees or higher during the day. Because of the war much of civilization was destroyed. Society has slowly rebuilt itself, technology has now reached a 1920's or 30's level (although often fantastical -"steampunk" type technology). There is little in the way of central governments, most of civilization consists of small towns and city states. Bounty hunters and mercenaries are relied upon to keep law and order. It is essentially a "pulp sci-fi/western" style campaign.

Being a pulp campaign I'm not that worried about scientific accuracy myself. However, several of the people that I play with are really into science. When something violates too much science without a reason, they let me know. So in interest of appeasing players, I would like to ask for a little help in designing the planet for my campaign. Specifically, being a desert planet what would this mean in terms of planet design? Little axial tilt? Proximity to the sun? Something else?
Also, being a desert, water is scarce and valuable on the planet. However, I plan to have some lakes and a small ocean. How could there be lakes and oceans, while still being a desert?
I plan to have an area called the "deadlands", which is basically an uninhabitable strip of land. There temperatures reach up to the 130, 140, degrees farenheit, or even higher. No living thing can survive there very long. Where would such an area be located? Near the equator?
Anything else to help with planet design?

I'll give you some help, but remember one important thing: it's your world. That said, here's some answers to your questions.

Deserts are usually a result of climate and geology, specifically, rainfall, wind, and soil errosion. Little rainfall would leave little plant life to hold the soil together against rain and wind. If you have a desert planet, it'd only be about 90% arid. At the poles, you'd have better climate and better terrain, if the world's average temperature is hot enough (from the sounds of it, it is). If you want the planet to remain like this and not recover for any good period of time (say, for several thousand years at least), give little axial tilt (Earth's is 23 degrees, so around 10 or less would work to allow only the climate and plant life to eventually reclaim the desert). Placing it closer to the sun would mean that, even before the war, the planet would've been a desert (if too little water) or jungle (if you have levels like on Earth).

From the sounds of it, everything else is good. The limited water of a few lakes and even a small ocean isn't too hard to fathom on a desert world. The water simply concentrates into these regions. However, if the world was an Earth-like one before, you might consider deciding on what happened to the excess water before your players question that, if they're as scientifically picky as you said. The Deadlands region would be best in the equatorial belt and could provide an interesting conundrum if this Deadlands wraps around the entire equator. If it separates the northern and southern hemispheres, you could have an unusually interesting set of cultures and the PCs might one day want to know "what's on the other side".

If you have any further questions or even need more help, just post it in here and I'll try or someone else will try to help.

Stealing a page from Diane Duane's Spock's World, perhaps this planet was once much more hospitable to life, but a burst of unusual solar activity stripped the planet of much of its water.

On our world, water is often split into hydrogen and oxygen high in the upper atmosphere, and the lighter hydrogen is sometimes lost to space. As a result, Earth is slowly becoming drier and drier. In fact, it's thought that life on Earth will be lost due to insufficient water much earlier than the Sun will cool sufficiently to swallow it.

In the history Duane envisioned for Vulcan, the planet's primary became hyperactive for a brief period tens of thousands of years ago when its fusion reactions destabilized. The sudden burst of light and heat destroyed much of the planet's life and stripped away much of the atmosphere and water. As a result, the formerly lush and verdent planet that was mostly covered by warm, shallow oceans became a parched world with a thin atmosphere. There were rare lakes and a few seas as large as our Mediterranean, but most of Vulcan grew to resemble the more unpleasant parts of America's southwestern deserts - a vast stony wasteland where rain fell rarely and water was the most important necessity for life. A cool spring's day could be well into the 90's, and a hot day could be 140 degrees Fahrenheit in the shade. Due to the lack of cloud cover that would help keep in heat, nights could be bitterly cold.

That's a fairly plausible mechanism by which a planet could come to have mostly desert conditions yet still have developed life. There are of course other ways - for example, Mars seems to have been a wet and relatively warm place once, but it's barren now. It's been a staple of science fiction and has become somewhat of a cliche, so perhaps a Mars-like world isn't what you're looking for, though.

Thanks for the input!
I have a few more questions:
1. Would a lake or ocean create a lot of rain? I'm thinking that the water would evaporate and eventually condense into rain. Perhaps some mountains seperating the water from the rest of the world.

2. I've heard in a lot of deserts it gets fairly cold at night because of lack of humidity to retain heat. Is this true? If so, what would the temperature variation be?

Anyway, I'm already getting some good ideas for my campaign!

shadow said:

Thanks for the input!
I have a few more questions:
1. Would a lake or ocean create a lot of rain? I'm thinking that the water would evaporate and eventually condense into rain. Perhaps some mountains seperating the water from the rest of the world.

Click to expand...

Not really. There would be significant evaporation, but that evaporation wouldn't condense back into rain for a while. The areas immediately surrounding the lake might be more rainy than general, but the effect would be fairly limited.

2. I've heard in a lot of deserts it gets fairly cold at night because of lack of humidity to retain heat. Is this true? If so, what would the temperature variation be?

Click to expand...

Yes. The difference between day and night temperatures varies, but some deserts can have an air temperature of 40-50 degrees Celsius during the day and -4 degrees at night. I think the Southwestern deserts of North America frequently drop to 40 degrees Fahrenheit or lower.

Large bodies of water will evaporate, yes. The water will stay suspended in the air, more or less. If the air stays low, it'll probably form dew and mists and such and create a fairly nice region. If it rises, the air's capacity to hold water drops, which is why clouds happen above the ground - that's the pressure threshold for water retention, where it moves from suspension to tiny droplets, and if the droplets collide enough, it forms rain.

A series of hills making the air go up and down could shake the water out of the air; and a mountain range could (should) be higher than the droplet point, so little water makes it past. Basically, rough terrain stops water.

Bear in mind that even the harshest desert of our world occasionally gets rain, once every few years or decades. Flash floods and narrow, deep culverts through hard-packed desert soil are typical features. (Dune country, obviously, won't retain these flood marks long.)

Salt will build up in bodies of water with no great circulation or way out. Look at the Dead Sea. The process of evaporation will concentrate minerals that have washed into a body of water, and the minerals have nowhere to go. Bear in mind, however, that before the cataclysmic water loss, there will have been a great deal more water on the world, and, without water erosion (still with sand and wind erosion, but water's the biggest factor), the empty riverflats, canyons, and maybe even continental shelves will be far more visible than before.



Deserts at night do get cold, and I guess humidity would be the dominant factor. Earth (rocks and sand, in the case of a desert) isn't a great conductor; the heat it picks up in the day spits back out the moment the sun goes down, and there's no cloud cover or water-saturated air to retain that heat. I don't have figures on me, but I think it gets cold enough to see your breath mist up. See if you can find some weather reports online.

Also bear in mind that deserts aren't necessarily hot during the day - they're just waterless places where nothing can grow, because of the aforementioned air currents not bringing rain or because no rivers run through it. A high-altitude or non-equatorial desert could be very cold even at midday, if the wind was up (wind is the most important chill factor; you can sunbathe in a bikini in Antarctica if the wind is low).

Water (and, I believe, water-filled organic entities like the tree) regulates temperature, so coastal regions are likely to be more moderate than desert regions. Not necessarily temperate; the latitude is more important here, because it determines how much sunlight the water can soak up.



There, hope some of that's useful... meteorology was my forte at flight school, even if I have forgotten chunks of it.