Tidally Locked Exoplanets and Habitability

[Wanderlust]

Article: http://arxiv.org/PS_cache/arxiv/pdf/1105/1105.1031v1.pdf

http://www.universetoday.com/85474/update-on-gliese-581ds-habitability/#more-85474

The new investigation was called for because Gliese 581d is suspected to be tidally locked. If so, this would create a permanent night side on the planet. On this side, the temperatures would be significantly lower and gasses such as CO2 and H2O may find themselves in a region where they could no longer remain gaseous, freezing into ice crystals on the surface. Since that surface would never see the light of day, they could not be heated and released back into the atmosphere, thereby depleting the planet of greenhouse gasses necessary to warm the planet, causing what astronomers call an “atmospheric collapse.”.

A new study indicates that planets that are tidally locked to their stars may not be habitable due to a permanent night side. The atmosphere would freeze out on the coldest parts of the night side causing a collapse of the atmosphere. The gas molecule that fall out could not be reheated back into the atmosphere, trapping them permanently.

This has implications for the estimated number of habitable planets.

 

[KJbushway]

Well, first impressions are whats new. I don't think you would see many people taking back what they said when it comes to the universe or our galaxy having the possibility of life. The number of habital planets would stay the same, no scientist would put a figure out and include those kinds of planets.

 

[Skywalker]

I thought it might be possible to live on a tidally locked planet if you kept your settlements on the terminator between the day side and night side. Or is that just sci-fi wishful thinking?

 

[YellowSubmarine]

You can live there all right. Can you evolve there?

 

[Jadzia]

I thought it might be possible to live on a tidally locked planet if you kept your settlements on the terminator between the day side and night side.

Would that be similar to being at the north pole on earth?

There would presumably be some downward convection of the atmosphere along the terminator, with the cold air at ground level circulating back towards the planet's hot spot.

What a tidal locked world may provide is some stability, because unlike a rotating planet, you wouldn't have to suffer extreme daytime highs and extreme nighttime lows. You could just choose whatever location is comfortable, and settle there.

The cold side will have frozen materials, like water, and you could mine these out and transport it back home to use.

It may be possible to construct a pipeline to extract that water automatically. Imagine a small pipe fitted inside a fatter pipe. Now inject hot gas through the fat pipe from the hot side of the planet. It flows through the pipeline to the cold side of the planet to melt the ice, and the melt water is pumped through the thin pipe back home.

 

[KJbushway]

In that case why not just build a big huge mirror on the dark side of the planet so that it can reflect the sun's energy and heat to the frozen side.

 

[Colonel Midnight]

I thought it might be possible to live on a tidally locked planet if you kept your settlements on the terminator between the day side and night side. Or is that just sci-fi wishful thinking?

One of the planets mentioned in the original Foundation series was like that. I want to say it was in the Second Foundation book, but may be mistaken. Always thought it was a neat idea...

Cheers,
-CM-

 

[Myasishchev]

You've always got potentially habitable moons of tidally locked exoplanets, yeah?

 

[KJbushway]

Depending on what side the moon is on and its orbit, along with distance from the sun itself.

 

[scotthm]

In that case why not just build a big huge mirror on the dark side of the planet so that it can reflect the sun's energy and heat to the frozen side.

If you're going to be travelling the galaxy looking for planets to live on why not just find a decent one to begin with?

---------------

 

[KJbushway]

^ that was my point.

 

[Argus Skyhawk]

There would presumably be some downward convection of the atmosphere along the terminator, with the cold air at ground level circulating back towards the planet's hot spot.

The point of the original post was that the atmosphere would collapse entirely because the atmospheric molecules on the cold side of the world would freeze and never again thaw. More atmospheric molecules would drift over from the warm side and freeze, and this would continue until no atmosphere was left.

 

[Argus Skyhawk]

If you're going to be travelling the galaxy looking for planets to live on why not just find a decent one to begin with?

That might be easier said than done. Trying to find a non-Earth planet with a breathable, nontoxic atmosphere, gravity close to 1G, and tolerable temperatures, could turn out to be like trying to find a very tiny needle in a mind-bogglingly huge haystack.

 

[Jadzia]

There would presumably be some downward convection of the atmosphere along the terminator, with the cold air at ground level circulating back towards the planet's hot spot.

The point of the original post was that the atmosphere would collapse entirely because the atmospheric molecules on the cold side of the world would freeze and never again thaw. More atmospheric molecules would drift over from the warm side and freeze, and this would continue until no atmosphere was left.

I didn't realise you meant oxygen/nitrogen would freeze too.

A thought experiment for you:

The cool side would have to get down to −210 °C for nitrogen to freeze, and even at that temperature, there would likely be some sublimation back into vapour (atmosphere) as it would be sitting in a vacuum. Geothermal energy may also play a role in preventing temperatures falling that low.

So if there is that thin atmosphere, it would shroud the planet, meaning there would be convection currents.

If there is convection, then those currents would carry warm gas to to the cold side of the planet, where it would raise temperatures above -210°C, causing oxygen/nitrogen to melt and form a sea.

That sea would spread to level itself and flow towards to warm side of the planet, where it would boil and thicken the atmosphere considerably.

 

[scotthm]

Trying to find a non-Earth planet with a breathable, nontoxic atmosphere, gravity close to 1G, and tolerable temperatures, could turn out to be like trying to find a very tiny needle in a mind-bogglingly huge haystack.

I'm quite sure it would be, but then the odds against humans ever travelling to other stars is mind-bogglingly huge.

A thought experiment for you:

...
That sea would spread to level itself and flow towards to warm side of the planet, where it would boil and thicken the atmosphere considerably.

Since we're just guessing, I think an atmosphere would most likely condense into very shallow seas and not into a large ocean.

---------------

 

[sojourner]

Depending on what side the moon is on

LOL, what? you do know moons orbit?

 

[Argus Skyhawk]

I didn't realise you meant oxygen/nitrogen would freeze too.

I didn't, but the person who wrote the OP did.

A thought experiment for you:

The cool side would have to get down to −210 °C for nitrogen to freeze, and even at that temperature, there would likely be some sublimation back into vapour (atmosphere) as it would be sitting in a vacuum. Geothermal energy may also play a role in preventing temperatures falling that low.

So if there is that thin atmosphere, it would shroud the planet, meaning there would be convection currents.

If there is convection, then those currents would carry warm gas to to the cold side of the planet, where it would raise temperatures above -210°C, causing oxygen/nitrogen to melt and form a sea.

That atmosphere you describe would be too extremely thin to warm the planet noticeably. I wouldn't expect it to form any sea.

That sea would spread to level itself and flow towards to warm side of the planet, where it would boil and thicken the atmosphere considerably.

Well, I'm not one of the scientists that performed the study that the OP was talking about, so who knows.

 

[Distorted Humor]

Article: http://arxiv.org/PS_cache/arxiv/pdf/1105/1105.1031v1.pdf

http://www.universetoday.com/85474/update-on-gliese-581ds-habitability/#more-85474

The new investigation was called for because Gliese 581d is suspected to be tidally locked. If so, this would create a permanent night side on the planet. On this side, the temperatures would be significantly lower and gasses such as CO2 and H2O may find themselves in a region where they could no longer remain gaseous, freezing into ice crystals on the surface. Since that surface would never see the light of day, they could not be heated and released back into the atmosphere, thereby depleting the planet of greenhouse gasses necessary to warm the planet, causing what astronomers call an “atmospheric collapse.”.

A new study indicates that planets that are tidally locked to their stars may not be habitable due to a permanent night side. The atmosphere would freeze out on the coldest parts of the night side causing a collapse of the atmosphere. The gas molecule that fall out could not be reheated back into the atmosphere, trapping them permanently.

This has implications for the estimated number of habitable planets.

Would be easy to terraform however...

 

[KJbushway]

Depending on what side the moon is on

LOL, what? you do know moons orbit?

Yes I do. Just to let you know I am having fun with this thread. I said what I had to say seriously in the beginning since then I have been having fun.

 

[Brandonv]

What about the habitability of tidally locked exomoons? They would have a day and night cycle, albeit a long one. If Earth sized moons like Pandora or Endor really existed, I wonder what effects the long days would have on weather patterns?