Atmosphere on a hypothetical tidally-locked Earth

[cephron]

Hey all, I have a few questions about the effects of tide-locking on a planet's atmosphere. Any insights or estimates would be helpful. Thanks!

(Assume, hypothetically, that an earth-like world was tidally locked to its sun--the day side would be perpetually blazing hot, and the night side freezing cold)

1) Would all the water end up trapped as ice on the night side?
Would sublimation of ice be enough to keep some in the atmosphere?

2) Might even carbon dioxide or other atmospheric gasses freeze/liquefy on the night side?

3) Suppose the planet had oceans like earth; would heat diffusion through the ocean be even close enough to keep the night side ocean liquid?

4) Only one side of the planet receives heat...and because of the super-slow rotation, we've probably lost a lot of coriolis force. Under these conditions, would there even be prevailing winds?

5) Suppose the planet still had a moon equivalent to ours...is it still possible for it to be tidally-locked to its primary?

Thanks for any input. :)

 

[Wanderlust]

I would think any moon would be unstable that close to a star. None of the (tidally locked) moons in our system have a moon.

I think there would be significant atmospheric circulation, so perhaps the atmosphere would transfer heat.

Question for others: Would outgassing be enough to sustain an atmosphere that is constantly freezing on one side of the planet?

 

[cephron]

@Wanderlust: I'm hoping distance from primary shouldn't be a problem...the hypothetical planet should be more-or-less Earth's distance from the sun, but with sufficiently asymmetric mass concentrations in it such that it would be locked at such distance. Does that make sense?

Thank you for your input on atmosphere...could you perhaps expand on why you think there would be significant circulation? While I'm no meteorologist, I understand coriolis force and the rhythmic heating of air around the Earth to be the main driving forces for weather.

 

[Wanderlust]

@Wanderlust: I'm hoping distance from primary shouldn't be a problem...the hypothetical planet should be more-or-less Earth's distance from the sun, but with sufficiently asymmetric mass concentrations in it such that it would be locked at such distance. Does that make sense?

Oh okay, usually when people say tidally locked I assume a planet around a red dwarf or very close to the star or other object. I am not sure, i would think tidal forces from the moon would disrupt tidal locking in small amounts. That last It would be interesting to see what the experts on the board say.

Such a planet would have started with a very slow rotation rate. That brings up another interesting idea, could Venus become tidally locked soon with its slow rotation rate?

Thank you for your input on atmosphere...could you perhaps expand on why you think there would be significant circulation? While I'm no meteorologist, I understand coriolis force and the rhythmic heating of air around the Earth to be the main driving forces for weather.

Im no expert on it as I am only a generalist, but I've read that the vast temperature difference would produce very large circulation systems convecting heat on the planet. Ie massive continuous wind storms at the terminator.

 

[qraal]

Hey all, I have a few questions about the effects of tide-locking on a planet's atmosphere. Any insights or estimates would be helpful. Thanks!

(Assume, hypothetically, that an earth-like world was tidally locked to its sun--the day side would be perpetually blazing hot, and the night side freezing cold)

1) Would all the water end up trapped as ice on the night side?
Would sublimation of ice be enough to keep some in the atmosphere?

1 (a) No, as oceanic currents would convey warmth, just like heat transport from the Earth's equator to the Poles.
1(b) Sublimation is negligible below 140 K. But I doubt it'd ever get that cold.

2) Might even carbon dioxide or other atmospheric gasses freeze/liquefy on the night side?

Not likely. Enough CO2 to freeze would likely cause too much heat to be transported. No way would oxygen or nitrogen freeze. Would never get cold enough.

3) Suppose the planet had oceans like earth; would heat diffusion through the ocean be even close enough to keep the night side ocean liquid?

See 1(a). Sea-ice would form, but the heat from below would mean it remains relatively shallow.

4) Only one side of the planet receives heat...and because of the super-slow rotation, we've probably lost a lot of coriolis force. Under these conditions, would there even be prevailing winds?

From sub-solar to the anti-solar point. A huge Hadley cell would form. Thus there would be wind. Wind is powered by thermal gradients NOT Coriolis forces. Those cause rotating weathering systems - i.e. a source of vorticity - but don't power the winds.

5) Suppose the planet still had a moon equivalent to ours...is it still possible for it to be tidally-locked to its primary?

A Moon could exist, but it would ultimately spiral into the planet, as tides from the Moon acting on a much slower rotating planet would act as a brake on the Moon, not the planet. The Moon would also need to orbit well within the planet's Hill Sphere else it would be lost via perturbations.

Thanks for any input. :)

You're welcome.