[GURPS Space(/Fantasy??)] Consequences of a Unique Planetary Rotation

[LazarusDarkeyes]

Given: Through ANY extra-ordinary means (magical, divine, whatever), a planet rotates so that it has the exact same hemisphere of the planet always facing its sun. The axis of the planet's rotation is exactly perpendicular to the plane of its revolution around the sun. The pleny is otherwise Earth is all other respects (days per revolution, size, mass, distance from sun, 1 satellite orbiting which is the size of the moon, etc.).

Question: What would be the effects of this? Would one side of the planet be a desert, the other side a frozen wasteland, and there might be a ring around the planet which is intermediate and may actualyl be habitable?

Affect on oceans? Polar icecaps? Flora/Fauna? Atmosphere? Other?

[nerdvana]

Aurore from 2300ad (a ring of habitable area) or the home of the Proximans in Morgan Press' Terran Trade Authority RPG. More on the first as it is easier to consult...

In the case of Aurore the planet is in orbit of a gas giant, but the effects would be similar. There is what is called the High Desert, a temperate zone running though the poles and about the planet between them and a glacier on the other side of the world from the hot side desert.

[Dragondog]

What I know:
* Half the world would have perpetual day and the other half perpetual night
* There will be no seasons

What I guess:
* The dark side would have problems with plant growth and oxygen production; it would be colder
* The light side wouldn't be a desert

[capnq]

I believe that any habitable zone along the solar terminator will have constant strong winds blowing from the night side to the day side. (I think there will be a comparable counterflow somewhere in the upper atmosphere, but I have no idea at what altitude.)

[Kyle Aaron]

If the orbit is not perfectly circular, there'd still be seasons of a kind.

How the continents are laid out will make a difference. For example, if the sunward side has a large ocean, evaporation from this will create rainfall along its coasts, or if it's too hot for rainfall, still there could be clouds which change the temperature here and there.

The presence or absence of sizeable moons will make a big difference to the climate, too.

[Mgellis]

Originally Posted by LazarusDarkeyes

Given: Through ANY extra-ordinary means (magical, divine, whatever), a planet rotates so that it has the exact same hemisphere of the planet always facing its sun. The axis of the planet's rotation is exactly perpendicular to the plane of its revolution around the sun. The pleny is otherwise Earth is all other respects (days per revolution, size, mass, distance from sun, 1 satellite orbiting which is the size of the moon, etc.).

Question: What would be the effects of this? Would one side of the planet be a desert, the other side a frozen wasteland, and there might be a ring around the planet which is intermediate and may actualyl be habitable?

Affect on oceans? Polar icecaps? Flora/Fauna? Atmosphere? Other?

In other words, a tidally locked planet.

Recent scientific studies suggest that, even when a world is tidally locked, heat would be transferred from the Day side to the Night side by oceans and the atmosphere.

GURPS Space actually covers such worlds. Using the rules in that book, the average temperature difference between Day and Night sides will be about 200 degrees. So...just a guess here...deserts (with forests in coastal regions) on the Day side and arctic wilderness on the Night side seems likely.

[Fred Brackin]

Originally Posted by Mgellis

GURPS Space actually covers such worlds. Using the rules in that book, the average temperature difference between Day and Night sides will be about 200 degrees.

That 200 degrees (which better be Fahrenheit) is a huge swing and obviously means that no more than one side of the planet has even a vague possibility of liquid water. If it runs 220 F on the day side and 20 F on the night side _neither_ side could have liquid water.

At Earth's distance from an equivalent star I think you need to write off the dayside. That side is likely to be much hotter than Earth and you'd have to be very lucky to keep it below boiling.

This is a big problem vis a vis photosnythesis. Nothing even remotely Earthlike is going live at an _average_ temprature above the boiling point of water. Even the extremophiles that live in the ocean floor's thermal vents straddle the transition zone and keep their average temp below boiling.

So I think the place is uninhabitable. With anything like Earth's amount of surface water it probably went runaway greenhouse with all the water vapor in the air. It might not be quite as a bad as Venus.

Even if it's not greenhouse I think you're looking at a non-oxygen atmosphere.

[David Johnston2]

Originally Posted by Fred Brackin

That 200 degrees (which better be Fahrenheit) is a huge swing and obviously means that no more than one side of the planet has even a vague possibility of liquid water. If it runs 220 F on the day side and 20 F on the night side _neither_ side could have liquid water.

.

Except of course those temperatures would only be at the west and east poles. It's like expecting to find liquid water in Antartica. That you can't doesn't mean you can't find it anywhere in the southern hemisphere. And of course there's the cooling effect of evaporation. Assuming the east pole isn't above sea level then you will have water there. It will just be boiling water which will flow outward with the air and rain back down as things cool down, while water continuously flows in to replace the boil-off. And below the surface things will cool down. It'll only be the top layer which boils. And of course the thicker the atmosphere, is, the less the temperature variance is.

[vicky_molokh]

I wonder if all this will cause changes in the magnetic field, ozone layer, and other factors which will have interaction with issues of radiation.

[Fred Brackin]

Originally Posted by Molokh

I wonder if all this will cause changes in the magnetic field, ozone layer, and other factors which will have interaction with issues of radiation.

Under our current understanding, no rotation means (mostly) no magnetic field. Not disastrous to surface life (if the temperatures permit) but there might be issues about the solar wind eroding the atmosphere at its upper limits.

If you have O2 in your atmosphere and the sun puts out UV, then the ozone is self-perpetuating.