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Bad Ronald
2011-Oct-11, 09:22 PM
What would the climate & weather be like on an Earth like exoplanet which was 50% land & 50% water. On this hypothetical planet the entire western hemisphere is land & the entire eastern hemisphere is water. This planet has the same mass, surface gravity, & atmospheric pressure as Earth, & orbits at 1 A.U. from a star that's a twin of the Sun. Also, this planet has a moon like our Moon, & has a 24 hour rotation period.

korjik
2011-Oct-11, 10:38 PM
most of the land will be desert.

astromark
2011-Oct-11, 10:39 PM
Its a interesting thought that... if earth had a different land mass distributional balance the climate would be different..

Just open the Atlantic to the Pacific from say Panama to Mexico and the climate here would change.

Your question is interesting.. But we will not find another Earth. The chance of this happening twice is very slim

Just as if it did.. Chance of finding such planet.. nil. The weather here is fickle..

our ability to make weather prediction is suspect.. here and we know much of this place..

imagining what we might find is open to many if's..

WayneFrancis
2011-Oct-12, 12:17 AM
most of the land will be desert.

Would it? Pangea wasn't thought to be mostly desert. Granted not quite 1/2 the globe tho.

To the original poster, if the planet is still geologically active then a super continent like this is not stable. The internal forces will promote the break up of such a super continent. If the planet wasn't geologically active then I'd expect that it would quickly, in astronomical terms, become tidally locked to its star promoting the desert Korjik suggests from 24/7 daylight and massive ice sheet on the far side.

That is my first guess.

Noclevername
2011-Oct-12, 12:29 AM
If the planet wasn't geologically active then I'd expect that it would quickly, in astronomical terms, become tidally locked to its star promoting the desert Korjik suggests from 24/7 daylight and massive ice sheet on the far side.

That is my first guess.

The OP specifies a 24 hr. rotation.

Romanus
2011-Oct-12, 02:24 AM
To echo WF, if it has plate tectonics like Earth, such a supercontinent would quickly break up--though it would probably reform occasionally.

WayneFrancis
2011-Oct-12, 02:55 AM
The OP specifies a 24 hr. rotation.
And I was pointing out that it probably wouldn't stay in a 24 hr day night cycle very long. Hmmm though with a moon it has other issues too.

But if you just want an Earth twin then just look at what Earth was like and did. Mind you that the climate back then was different to because of different ratios of gases within the atmosphere.

Noclevername
2011-Oct-12, 03:10 AM
And I was pointing out that it probably wouldn't stay in a 24 hr day night cycle very long.

Why not? It would still have the same amount of rotational energy to shed as Earth does, whether tectonically active or not.

WayneFrancis
2011-Oct-12, 04:45 AM
Why not? It would still have the same amount of rotational energy to shed as Earth does, whether tectonically active or not.
Because the non uniform mass distribution of dense material will slow its rotation down. That is why moons become tidally locked to their planets. Mercury has done this too.I believe Venus has lost most of its rotational energy in other manners. The more pronounced the mass difference the faster the object will tidally lock to its parent. This energy is conserved so it will lift the smaller bodies orbit I believe too.

korjik
2011-Oct-12, 05:22 AM
Would it? Pangea wasn't thought to be mostly desert. Granted not quite 1/2 the globe tho.

To the original poster, if the planet is still geologically active then a super continent like this is not stable. The internal forces will promote the break up of such a super continent. If the planet wasn't geologically active then I'd expect that it would quickly, in astronomical terms, become tidally locked to its star promoting the desert Korjik suggests from 24/7 daylight and massive ice sheet on the far side.

That is my first guess.

I thought most of Pangea that was away from the oceans was considered to be desert. Then again, most of Siberia is fairly close to desert, but that dosent mean no vegetation, just that there isnt alot of rain. Assuming that there was sufficient water flow to the interior, the interior of the continent could be a pretty lush desert.

The OP did say that the condition was an entire hemisphere is land and one is ocean. I would think that would be pretty deserty in the middle of the continent. If it were a more irregular continent, with large bay-ish seas and small oceans, then there it would be alot more lush.

korjik
2011-Oct-12, 05:24 AM
Because the non uniform mass distribution of dense material will slow its rotation down. That is why moons become tidally locked to their planets. Mercury has done this too.I believe Venus has lost most of its rotational energy in other manners. The more pronounced the mass difference the faster the object will tidally lock to its parent. This energy is conserved so it will lift the smaller bodies orbit I believe too.

Technically, the OP is setting the conditions at the time to be considered. The conditions before and after may have been quite different.

I think that there is a bit of a consensus that this super-pangea setup would break up pretty quickly, or at the very least the super-pangea would migrate to one of the poles to minimize the moment of inertia.

EDG
2011-Oct-12, 08:54 PM
Because the non uniform mass distribution of dense material will slow its rotation down. That is why moons become tidally locked to their planets. Mercury has done this too.I believe Venus has lost most of its rotational energy in other manners. The more pronounced the mass difference the faster the object will tidally lock to its parent. This energy is conserved so it will lift the smaller bodies orbit I believe too.

I think you're confusing tidal braking with obliquity change. IIRC an asymmetrical distribution of mass on a planet's surface (e.g. with a supercontinent on one hemisphere) could make it more inclined (hah!) to precess around its axis or gradually change the axial tilt so that the extra mass is shifted towards the equatorial regions (I think? It should want to align with the tidal bulge IIRC?). Some have theorised that this may have happened to Earth on one or more occasions in the past.

It might affect tidal braking of the planet by solar tides if the solar tides are significant enough, but the planet would have to be closer to the star for this to be a possibility. Tidal braking isn't due to a "non-uniform mass distribution of material" at all though (also, continental crust is actually less dense than oceanic crust), it's due to the fact that there's a lag angle between a rotating primary and its orbiting satellite, which results in the dissipation of energy inside both bodies (which manifests as tidal heating, and the transfer of angular momentum).