180 Degrees

As two possible alternatives, if you can't find physics to support this model...

What about 150-180 degrees of tundra, with the planet "bleeding" enough heat at its poles to support a relatively diverse biosphere. Or else an aqua planet with land masses at the poles?

Matt, as I understand it, Earth is optimum for life as we know it (ie: human life, etc), and it is so because of its size, location from its star, and atmosphere.

Things that could change that are, as you said, increasing the planet's size (although that might cause gravitational problems), moving it somewhat closer to the star (but not too close--Venus is inhospitable), making the star hotter.

An interesting option is what Vinge did in "A Deepness in the Sky" where the alien planet's star "turned on and off" on a cyclic basis...and life evolved there to withstand the extremes of terrible cold and extreme heat.

You might also consider making your planet more arid than Earth to begin with. Lack of great oceans would cause the climate to warm up considerably.

Sounds fun...can't wait to see what you decide. Good luck.

I could be wrong about this, but I believe one reason the Earth doesn't have this problem is due the axis tilt. A loss of all tilt might make the equitorial regions desert-like.

I wouldn't do the on-off star, if only because it's already been done so well by Dr Vinghe

Until someone told me otherwise, I wouldn't even worry about the conditions that might cause such a status. Instead, I'd just do it. I'd make the people on the ground accept this as part of their reality. Infodumps are no good, anyway. Why worry about the details from space when the details on the ground are the source of the story?

Perhaps look at the history of some existing deserts. I vaguely recall reading that the Sahara didn't used to be desert a long time ago. I'd also suggest looking into the geological conditions surrounding areas like Death Valley, too.

Throwing out ideas from the top of my head from vaguely remembered high school science classes.... One reason a desert might form is because there's a mountain range preventing the water from reaching the area. Prevailing winds send the clouds toward the mountain range which captures the moisture in terms of rain and snow, thereby "starving" the other side of the range. Perhaps some great cataclysm in the past caused a very high mountain range to form? The other side of the mountain might become desert.

Vaguely on topic - would it be too big a stretch to have technology turn a moon of a planet (semi-planet) like Pluto into a vast nuclear reactor so that it acts like a miniature sun for a cold planet, except that this "sun" circles its world?

Jenny said:

Vaguely on topic - would it be too big a stretch to have technology turn a moon of a planet (semi-planet) like Pluto into a vast nuclear reactor so that it acts like a miniature sun for a cold planet, except that this "sun" circles its world?

Click to expand...

2010 by Arthur C. Clarke might be of interest to you. I'm not sure if what you're proposing would work.

TheIT said:

Perhaps look at the history of some existing deserts. I vaguely recall reading that the Sahara didn't used to be desert a long time ago. I'd also suggest looking into the geological conditions surrounding areas like Death Valley, too.

Click to expand...

Good call... climates have varied tremendously over history - but then again, so have the positions of the continents themselves. Plate tectonics and all, if you looked at the earth of a few hundred million years ago, you'd see a different planet.

TheIT said:

Throwing out ideas from the top of my head from vaguely remembered high school science classes.... One reason a desert might form is because there's a mountain range preventing the water from reaching the area. Prevailing winds send the clouds toward the mountain range which captures the moisture in terms of rain and snow, thereby "starving" the other side of the range. Perhaps some great cataclysm in the past caused a very high mountain range to form? The other side of the mountain might become desert.

Click to expand...

There's actually a new theory about how surface weather can actually affect geology, from deep seepage of water and increased tectonic plate weight to related factors (like weight of glaciers).

If you can rationalize it with even a lick of sense, you can probably make it believable enough for a fantasy story.

Heck, there was another recent story about figuring out why a local moon had an unexplained bulge in the middle. The most recent theory was that the moon may have had it's own ring system at one time but gravity eventually pulled it in. You could use something like that -- and the material that was pulled in had odd environmental effects (toxic in some fashion) that led to a self-sustaining equatorial belt desert. If the fall was recent (last thousand years), you could even include all the lore/mythology that rose to explain the rings, plus the history of the cataclysm of the fall (and the mythological fallout/debunking because of the fall).

RJLeahy said:

I could be wrong about this, but I believe one reason the Earth doesn't have this problem is due the axis tilt. A loss of all tilt might make the equitorial regions desert-like.

Click to expand...

I'd tend to agree with this one. If the sun were to strike the equator constantly and equally day in and day out year after year it probably would burn up that part turning it to desert.

Question: does it have to be only at the equator? Or could the desert region be larger than that... Just wondering.

What about a saturn-like ring around your planet that is on the same axis as the sun so that the sun never shines at the equator, so then you'd have nothing growing there and it would be a different type of desert environment.

Also, you could have oasis's of volcanic vents, similar to the undersea vents, so you could invent land creatures that evolved by chemosynthesis.