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Still Waters

Most liveable alien worlds ranked

19 posts in this topic

Scientists have outlined which moons and planets are most likely to harbour extra-terrestrial life.

Among the most habitable alien worlds were Saturn's moon Titan and the exoplanet Gliese 581g - thought to reside some 20.5 light-years away in the constellation Libra.

The international team devised two rating systems to assess the probability of hosting alien life.

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The water under Saturns moon is what I find most interesting a bit possibility for some kind of life there I think :tu:

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The water under Saturns moon is what I find most interesting a bit possibility for some kind of life there I think :tu:

If you believe the "recipe" version of life, Enceladus has many of the ingredients. Unfortunately it doesn't appear to have a wide range of environmental conditions that promotes life.

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Some major speculation on the Gliese planets. Other than we have detected them we truly have no idea what they are like, bar an estimate of temperature. They have rated them more earth like than Mars. For all we really know they could be gas planets.

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meaningless.

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If you believe the "recipe" version of life, Enceladus has many of the ingredients. Unfortunately it doesn't appear to have a wide range of environmental conditions that promotes life.

Would a different type of life be able to exist under different enviromental conditions though?

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Would a different type of life be able to exist under different enviromental conditions though?

We don't know of any other "type" of life, so no one can answer that question with any authority.

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The existence of the highest-rated extrasolar planet, Gliese 581g is in considerable doubt. Some re-examinations of the radial velocity data do not find it at all. More radial velocity measurements will be needed to settle this matter. It is considered very unlikely that the planet, assuming it does exist, is a gas planet, like a smaller version of Neptune. With a mass of ~3.1 to 4.3 times that of Earth, it would be very unlikely to gravitationally retain such a large amount of the necessary light gasses. This is particularly so, since the planet is tidally locked to its star, with the same side always heated. This would increase the erosion from its atmosphere of the lighter gasses via stellar radiation. It's atmosphere would probably be somewhat denser than Earth's, but not greatly so, and made up of the heavier gasses typical of terrestrial planets-- nitrogen, oxygen, carbon dioxide, argon, and the like.

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This is particularly so, since the planet is tidally locked to its star, with the same side always heated.

The "freeze and fry" planets seem like the worst combination of extreme conditions for life.

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The "freeze and fry" planets seem like the worst combination of extreme conditions for life.

It's been calculated that atmospheric circulation could, in some cases substantially even out the extremes of temperature. This is what happens on Venus, which rotates so slowly as to be practically tidally locked. It's almost as hot all over the planet, as around the sub-solar point. They believe this could happen in much less dense atmospheres, too. Perhaps down to 1/10 the density of Earth's atmosphere. Given a planet well centered in its habitable zone, like Gliese 581 g is supposed to be, and tolerable temperatures might exist over much of the surface. Possibly a torrid zone, like our tropics, around the sub-stellar point, and a frigid zone opposite it on the planet, like one of our polar areas.

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I think we truely have no idea what conditions life could manifest from distant planets. for instance a organic being that uses photosynthesis as a way of reciving energy and no need of eating for nutrition. just a thought.... but then you wouldnt need a atmosphere that has more oxeygen than carbon dioxide it would be vise versa. Like i said just a thought, in another galaxy the laws over there might be completly different from the laws over here.

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meaningless.

helpful as ever.

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I think we truely have no idea what conditions life could manifest from distant planets. for instance a organic being that uses photosynthesis as a way of reciving energy and no need of eating for nutrition. just a thought.... but then you wouldnt need a atmosphere that has more oxeygen than carbon dioxide it would be vise versa. Like i said just a thought, in another galaxy the laws over there might be completly different from the laws over here.

i suppose the question is whether there'd be likely to be the resources and the raw materials needed to build a technological Civilisation, and then whether any intelligent beings would evolve in a form to be able to construct anything out of them; for that I suppose you'd need a physical body at the very least, and, people seem to consider, another thing that would be essential would be Thumbs. Without Thumbs, you wouldn't get anywhere. :no:

Edited by 747400

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It's been calculated that atmospheric circulation could, in some cases substantially even out the extremes of temperature. This is what happens on Venus, which rotates so slowly as to be practically tidally locked. It's almost as hot all over the planet, as around the sub-solar point.

Because it has a fluid and crushingly dense atmosphere that can't help but quickly conduct heat around the entire planet.

They believe this could happen in much less dense atmospheres, too.

I haven't read that and I can't find any example that supports that. Every model I've seen shows that thinner atmospheres away from the sun either quickly lose their heat to space before they can conduct it around the planet or trap the heat creating intense temperatures, depending on their distance from their sun. For example, lock the Earth to the sun and you end up with water becoming a greenhouse gas and it becomes something close to Venus.

It's really hard to make an atmosphere that's balanced like the Earth's. The tremendous amount of water here is very important and any kind of fluid on a planet would help.

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The Wikipedia article on Gliese 581 g has a reference to efficient heat transfer in even a 100 Millibar atmosphere, assuming sufficient greenhouse gases. There is also a link in the article to a scholarly article about this study. (footnote 23). link to the relevant section of the above Wikipedia article: http://en.wikipedia.org/wiki/Gliese_581_g#Tidal_locking_and_habitability see subsection on atmospheric effects, first paragraph.

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I haven't read that and I can't find any example that supports that. Every model I've seen shows that thinner atmospheres away from the sun either quickly lose their heat to space before they can conduct it around the planet or trap the heat creating intense temperatures, depending on their distance from their sun.

http://geosci.uchicago.edu/~rtp1/papers/Gliese581gPalletesApJL2011.pdf

This paper here shows a model with Atmospheric pressure equal to Earth's with 20% CO2 mixed with N for Gliese 581g having a tempurature gradient of only 110 K between day/night sides.

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http://geosci.uchicago.edu/~rtp1/papers/Gliese581gPalletesApJL2011.pdf

This paper here shows a model with Atmospheric pressure equal to Earth's with 20% CO2 mixed with N for Gliese 581g having a tempurature gradient of only 110 K between day/night sides.

Very strict (i.e. unlikely) conditions theoretically still resulting in a wide temperature variation by Earth standards.

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Awwwee Can i go?

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Very strict (i.e. unlikely) conditions theoretically still resulting in a wide temperature variation by Earth standards.

How so? It's a larger planet than Earth so out gassing could easily account for such a CO2 concentration and Nitrogen isn't going to be uncommon in Exo-Atmospheres so I don't see any unlikely conditions and at best that temp. gradient is only 15-20° Kelvin greater than what we might typically see here on Earth and about 20° K less than record hot/cold temps. set on Earth.

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