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Premise/question

Correct me if I'm wrong, or if humans have terraformed the planet by the time you're reading this, but Mars is mostly desert-like. It has large ice caps which contain most of its water, and the rest of the planet is basically dry rock and dust. If you want water when you're on Mars, your best bet is to get a pickaxe and put some ice chunks into your mouth to melt.

I like desert planets. They have a desolate feel to them which is extremely appealing, and they make for interesting story ideas. The only thing is, I don't want Mars's low temperature. In fact, I want equatorial regions to be at Sahara/Death Valley temperatures. You know, an archetypical scorching desert.

My question here is: can a planet have such a dramatic temperature difference so that the poles are covered in permanent ice, and yet have hot deserts at the equator, and what are the effects of this temperature gradient?

I'm not including information such as planetary radius, mass, volume, distance from sun, composition, and atmosphere for the simple reason that I have no idea what parameters are necessary for such a world to form. Feel free to use whatever values you want. However, I've included a list of restraints below, because there are certain attributes I want this planet to have in order to be viable in a story.

Notes/constraints:

  • This planet should be around the size of Earth.

  • Not sure if this matters, but there's no moon. There are rings, though.

  • The planet should be desert all of the way through, with little to no bodies of liquid water.

  • The ice should be easily accessible, i.e. not separated from the rest of the planet by impassable mountains.

  • If possible, there should be extensive aquifers in the upper temperate region.

  • There should be very strong winds on this planet, which means slower rotation.

  • The planet has minimal axial tilt.

  • Conditions in the temperate region should be survivable for lifetimes.

  • There should be naturally occurring life, for instance in karstic aquifers.

  • From outer space, the planet should resemble Mars.

  • If it's possible, there should be something profitable about this planet, linked to the temperature or ice. Think melange, but formed by hot/cold.

  • Finally, and arguably most importantly, handwaving should be kept at a minimum. I want there to be enough realism and gory details to write an uber-accurate encyclopedia on this planet.

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    $\begingroup$ We know for a fact that planets can simultaneously have icy poles and hot equators...because we happen to live on one such. Consider giving your planet a bit more greenhouse gas so it's steady-state temperature is a bit warmer, or move your planet a smidge closer to it's star. Or both. Remember that more atmosphere means more heat distribution in the form of winds. On Earth, water carries most of that heat around - on your planet, the winds might be a bit fierce. $\endgroup$ – user535733 Apr 19 '20 at 22:40
  • $\begingroup$ pg4919, while I read it was imagining your hot Mars. I think you will like to read too. $\endgroup$ – Rodolfo Penteado Apr 21 '20 at 11:03
  • $\begingroup$ Easily done, if you remove the atmosphere and its role in distributing heat across the planet. But that is in conflict with "very strong winds". Very strong winds imply an atmosphere that is moderately dense to very dense. Dense atmosphere implies high measure of heat transfer to/from the poles, which implies less temperature variation between poles and equator. $\endgroup$ – PcMan Dec 7 '20 at 12:12
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My question here is: can a planet have such a dramatic temperature difference so that the poles are covered in permanent ice, and yet have hot deserts at the equator, and what are the effects of this temperature gradient?

Yes. Mars need only a bit more of energy to meet the requirement you want. More close to the Sun or orbiting one star more brighter.

"Differing in situ values have been reported for the average temperature on Mars, with a common value being −63 °C (210 K; −81 °F). Surface temperatures may reach a high of about 20 °C (293 K; 68 °F) at noon, at the equator, and a low of about −153 °C (120 K; −243 °F) at the poles."

The effects are strong winds eroding the surface. A slow rotation means the planet hasn't a strong magnetosphere and is vulnerable to stelar winds depleting their atmosphere, like real Mars.

After solar winds blowed away the majority of martian atmosphere only heavy compounds remain there. Majority of water is heavy water, D2O instead H2O mixed with salts. Less atmosphere means less pressure then the water will evaporate with less heat. Since the planet is more hot than Mars its will dryer faster.

Depending of how active and hot was the planet interior, with the lose of weighth above the crust this one can expand and crack, releasing magma like a eruption of a megavulcano, like... like... the Tharsis Mons Pavonis, Arsia and Ascraeus, and the Olimpus Mons.

Life happened at past is almost all extinct, except some extremophiles underground. Petrified old life forms (vegetables? fungis? who knows?) looks like trees can be see in tropical latitudes.

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  • $\begingroup$ Thanks for the answer, this really helps. Any chance you know how to calculate polar and equatorial temperatures? $\endgroup$ – user75058 Apr 19 '20 at 23:53
  • $\begingroup$ @pg4919 Its tons of variables to build a model: amount of stelar radiation, atmosphere mass and composition, gravity, day lenght, etc. Unless happen to be something unexpected and different of Earth or Mars (a dry Earth or a hot Mars) the temperature gradient of both planets can be used as good glimpse. $\endgroup$ – Rodolfo Penteado Apr 20 '20 at 11:10
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It is possible for an hot Mars to exist. One of the homeworlds of the villains of my story, "Superhumans", comes from one such world.

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  • $\begingroup$ This appears to be a comment and not an answer to the question. $\endgroup$ – BMF Dec 7 '20 at 19:18
  • $\begingroup$ Well, it's possible for a hot Mars to support life, if it has sufficient mass and magnetism to hold onto an atmosphere, liquid water on the surface, and a relatively nontoxic atmosphere. $\endgroup$ – TysonDennis Dec 7 '20 at 20:32

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