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I am trying to build an "exotic" planet under currently known physics and chemistry laws.

Besides having an highly tilted revolution axis (which results in 1 day lasting 1 year), which other mechanism can be used to explain a planet where the polar regions have a warmer climate than the equatorial regions? Is it even realistic?

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    $\begingroup$ I don't know enough to make this an answer, but what if the planet had a dense ring that blocked enough sunlight along the equator such that the poles were warmer due to more sunlight exposure? $\endgroup$ – Jason K Feb 10 '17 at 16:02
  • $\begingroup$ @JasonK planetary rings are only few meters thick. Not even close enough to make any difference. $\endgroup$ – Mołot Feb 11 '17 at 21:34
  • $\begingroup$ @Mołot perhaps, but what if a moon was hit by an impact that broke it up? Maybe for a few thousand years there could be a dense ring, long enough to affect the planet below. Doesn't have to be an effect that lasts millions of years, just long enough for the ecology to adjust a bit. $\endgroup$ – Jason K Feb 13 '17 at 14:36
  • $\begingroup$ @JasonK well, I'm not sure how long it would take, but if OP doesn't need a stable solution, it makes sense. $\endgroup$ – Mołot Feb 13 '17 at 15:17
  • $\begingroup$ @Mołot Saturn's rings vary in thickness between 10 meters and 1 km. While that makes your comment technically not entirely inaccurate, you could increase the estimate by at least an order of magnitude and still be toward the lower end of the actual range. en.wikipedia.org/wiki/Rings_of_Saturn#Physical_characteristics $\endgroup$ – a CVn Feb 20 '17 at 7:42
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An amusing (but potentially not what you're after) possibility would be a planet orbiting a long way from the star so that solar energy isn't that much of a heat-giver. Potentially just having a really high albedo could have the same effect. If this planet also has high concentrations of long-life radioactive elements at the poles then you'll end up with warmer poles as the material decays.

If you had a reasonable atmosphere to insulate the material this would essentially turn your planet into the planetary equivalent of an RTG, turning nuclear power into work by heating the air at the poles which would then flow to the equator, cool and head back to the poles.

It would also irradiate pretty much anyone near the poles and carry the risk of occasional spontaneous explosions if large conglomerations of material form, but hey, you're after exotic!

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Perhaps this is possible by changing ocean currents through salinity

Disclaimer: This answer is all based on this article. I am not a climate scientist so perhaps others can argue otherwise.

How salty the ocean water are seems to effect how the currents carry heat.

On Earth, as the warm currents of the Gulf Stream reach the Arctic, they cool and sink, concentrating salt water into a supercooled briny current that flows along the ocean floor down towards the South Pole where more currents eventually bring those cold salty waters back up towards the surface. They eventually warm up, and start venturing north again, this time on the surface of the ocean.

If we dramatically increase the salinity of the water:

Our research shows that oceans on other planets with a much higher salinity could circulate in the opposite direction--with polar water flowing towards the equator at the surface, sinking in the tropics and traveling back towards the poles at depth. We also found a similar pattern emerging for freshwater oceans." Manoj Joshi, an author of the paper said "These circulation patterns are the opposite of what happens on Earth, and would result in a dramatic warming in the polar regions."

So this gives us a method for warming up the poles, not necessarily cooling the equator though. All we need is another method such as a higher altitude to cool the equator.

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  • $\begingroup$ Higher albedo at the equator, perhaps? $\endgroup$ – Joe Bloggs Feb 10 '17 at 12:17
  • $\begingroup$ @JoeBloggs Works to cool the equator but then we never gain the heat to put into the sea and take that warmth to the poles. Something like elevated land would mean our hot air can still provide the warmer currents but the air is thinner higher up so the land would be cooler. $\endgroup$ – Lio Elbammalf Feb 10 '17 at 12:23
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You can have poles hotter than the equator if your planet's rotational axis is tilted sideways on its orbit (see: Objects hotter at their poles than their equators?). This is not a sufficient condition, since our (only?) example in real life is the planet Uranus, and Uranus is in fact about the same temperature all over despite being tilted 98 degrees, but this is because atmospheric circulation seems to be redistributing heat, and also because there's so little heat from the Sun to begin with. Uranus also radiates a bit of internal heat, with further atenuates the differences.

Uranus is a gas planet, though; on a smaller terrestrial planet the much thinner atmosphere won't redistribute heat as thoroughly, and internal heat will also be much less. Oceans tend to moderate temperatures too, so the drier your planet is, the more it will respond to seasonal changes in solar irradiation.

Note: having a highly tilted axis doesn't result in "1 day lasting 1 year". The planet can rotate on its axis at any reasonable speed you want it to; only the amount of hours of dark and sunlight will give the appearance of long days or nights (as in Earth's polar regions).

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