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Could a planet be hot enough that oceans could form at the poles, but would boil at the equator? And would oceans form at all on this planet?

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    $\begingroup$ My gut feeling is that that hot enough to boil water at the equator would be well past the point of creating a runaway greenhouse effect and you'd end up with something more like Venus than Earth. Not an expert, however. $\endgroup$ Commented Apr 23, 2020 at 20:41
  • $\begingroup$ What if the water-boiling tempurature is caused by greenhouse effects around the equator (where the most vapour is)? $\endgroup$ Commented Apr 23, 2020 at 20:42
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    $\begingroup$ If instead you were to pursue a tectonic mechanism for this, then you might just find a way to have the ocean basins at the poles, and arid climate around the circumference that you don't get many lakes, rivers, or streams (those tend to come from glaciers and elevation anyway). $\endgroup$
    – John O
    Commented Apr 23, 2020 at 22:24
  • $\begingroup$ Read this as a supplement to the answer given by ESL. planetplanet.net/2014/10/10/… I recommend the whole planetplanet website for SF worldbuilders $\endgroup$
    – Jim Baerg
    Commented Apr 24, 2020 at 1:52

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I have doubts about boiling, but I think it's possible evaporation that do not require high temperatures. I think it's not enough with temperatures differences, but also terrain and climate conditions, like a big desert:

  • Less water volume than Earth (in proportion to surface).
  • Warm winds that drop most of the rains before the desert.
  • Mountains ranges that help the winds to drop rains and work as a barrier.
  • Soil transformation with high permeability (easy drain) and low retention, basically: sand.

Edit: The mountains ranges should be in the limit between the poles and the Big Desert, some kind of Rings. The winds that travel from the non-desert zones (near poles) to the mountains should be warms, AFAIK; so, there must be a warm zone before the Rings. Something like this (seen from both poles):

Map of poles

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    $\begingroup$ Where on the globe would the mountains, warm winds, and deserts be? $\endgroup$ Commented Apr 23, 2020 at 21:26
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    $\begingroup$ I expand the answer and include a map, @IchthysKing. $\endgroup$
    – ESL
    Commented Apr 23, 2020 at 22:03
  • $\begingroup$ I was posting a planet-sized heat pipe idea and a triple-point of water idea in the comments above when I realized that's pretty much what you described. This idea may work better with either with a single polar ocean or dual suns. $\endgroup$
    – Black
    Commented Apr 24, 2020 at 7:13
  • $\begingroup$ In essence, if we're boiling hot at the equator, it's already like Death Valley even in the equivalent of earth's temperate regions. No liquid water would be present anywhere near the equator, and any rivers flowing from the polar oceans would get fully absorbed by the ground and/or evaporate in the region marked "The Rings" ; no mountain ranges required to keep the water near the poles; a water cycle would do that, with any liquid water evaporating as it flowed from the poles towards the arid regions, and cooling air that approaches the poles causing the water to condense out as rain. $\endgroup$
    – Steve
    Commented Apr 24, 2020 at 9:26
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    $\begingroup$ Said cloud cover would also help keep the poles cool so that liquid water can remain there. $\endgroup$
    – Skyler
    Commented Apr 24, 2020 at 13:18
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A boiling liquid is not in equilibrium with its surroundings, it is constantly loosing vapour to the atmosphere. On a planetary scale this is not possible, boiling would continually increase the atmospheric pressure. This in turn would increase the boiling point of the water (as in a pressure cooker). This would continue until the water was all gone or until the increased temperature allowed sufficient heat to be radiated into space to allow a constant temperature to be maintained.

An additional problem would be the capacity of additional water vapour to trap heat (greenhouse effect) which could easily run out of control as happened on Venus.

So the answer to your question is no this is not possible. Oceans do not boil in the sense that kettles do, they act more like indestructible pressure cookers where the pressure release valve is stuck.

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  • $\begingroup$ But, for fun, you could have some springs near the equator, so they'd be constantly dumping steam into the atmosphere. $\endgroup$ Commented Apr 24, 2020 at 14:34
  • $\begingroup$ There is always the possibility for local effects that are not in equilibrium like geysers where very hot pressurised water suddenly finds itself under much lower pressure, but on a larger scale it wouldn't work. $\endgroup$
    – Slarty
    Commented Apr 24, 2020 at 15:38
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    $\begingroup$ Of course, there would need to be an equilibrium. Maybe "boiling" in the question was not the best term. But on Earth, every ocean is constantly evaporating to the atmosphere. However, the water is also constantly falling out of the atmosphere as rain/snow, so there is an equilibrium. I see no physical problem with a planet with an atmosphere with surface pressure 100 kPa, where the temperature near equator is 120 °C and the temperature near the poles is 80 °C. You can start with a dry planet and a dry atmosphere, if you like, and then put a bit of water in a bassin near one of the poles. $\endgroup$ Commented Apr 24, 2020 at 16:05
  • $\begingroup$ Boiling is the wrong word. Evaporation occurs at temperature below the boiling point when the partial pressure of the gas generated is less than that of the surrounding atmosphere. Evaporation can take place at any temperature. Boiling occurs when the partial pressure of the evaporating gas reaches atmospheric pressure. In your example adding water to the poles in on a dry planet at the temperature that you specify would lead to very rapid evaporation. At 80 degrees C approximately half the mass of the atmosphere would be composed of H20 and the boiling point of water would rise. $\endgroup$
    – Slarty
    Commented Apr 25, 2020 at 15:58

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