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View Full Version : Life bearing moons vs planets



Tom Mazanec
2014-Jan-27, 07:18 PM
I know there will be some handwaving in this, but assuming life is easy to start if you have liquid water, what percentage of life bearing worlds are moons as opposed to planets?

R.A.F.
2014-Jan-27, 08:00 PM
Since we have zero examples of satellites of Planets posessing life, I voted zero...

Solfe
2014-Jan-27, 08:38 PM
I would think that more investigation is needed to make any call.

Even without life, some of the water bearing moons in the solar system are very interesting just for having water. I would plug Titan into that group, too, even though the liquid isn't water.

Noclevername
2014-Jan-28, 12:29 AM
I know there will be some handwaving in this, but assuming life is easy to start if you have liquid water, what percentage of life bearing worlds are moons as opposed to planets?

It depends on how easy. 1% easy? 2% easy? etc.

IOW "easy" is such a subjective term as to be useless for answering this question. Roll 2d10 would be just as useful.

Aristarchusinexile
2014-Jan-28, 12:34 AM
Why does life require water?

Aristarchusinexile
2014-Jan-28, 12:37 AM
I would think that more investigation is needed to make any call.

Even without life, some of the water bearing moons in the solar system are very interesting just for having water. I would plug Titan into that group, too, even though the liquid isn't water.

Fits my "Why does life require water" exactly.

Local Fluff
2014-Jan-28, 11:34 AM
I count about 5 large water rich moons and another about 5 small icy moons and icy dwarf planets (not counting asteroid sized moons which often aren't icy anyway). That gives about 25% more moon:ish objects than planets. Of the planets I count 3 plus dwarf planets Pluto and Ceres as potentially habitable, because they have, had or could with minor changes in their destiny contain liquid water. So I'd guess about 50/50 between moons and planets, no less than 25/75 either way at least. The actual ratio is equally unknowable today.

A problem for moons might be that they get tidally locked to their planet (even our Luna which is by far the relatively largest moon relative to its planet is tidally locked) and that tends to boil off any atmosphere.


Fits my "Why does life require water" exactly.
Because the water molecule forms non-covalent bondings. It is bipolar and easily "gets inbetween" other molecules which want to marry by charing their electrons more permanently. This makes water a great dating site where for example aminoacids quickly can try out their fit to many different parts of an RNA molecule. If they don't make good enough covalent bondings, water will immediately be there to separate them until the next one comes along for a try.

Methane (on Titan) is as liquid as water and does transport stuff around. But it lacks the ability to interfer with how other molecules bond. Biochemical processes would be much slower in methane liquid than in liquid water. There are other potentially liquid bipolar molecules than water, but since water is the second most common molecule in the universe, on Earth and inside all known living beings, it'd be a bit far fetched to search for such alternatives. Even if it exists, water based life is likely to be ten or so times more common.

Noclevername
2014-Feb-01, 10:03 AM
A problem for moons might be that they get tidally locked to their planet (even our Luna which is by far the relatively largest moon relative to its planet is tidally locked) and that tends to boil off any atmosphere.

Titan disagrees. :)

Our Moon is dry and airless because it's too small to hold a significant atmosphere and is also too close to the Sun and too far from Earth, but for moons deeper in their planet's gravity well, individual molecules that escape can go into orbit around the primary planet, forming a gas torus, which lets them get re-captured later by the moon. Close orbits are good orbits, as far as atmospheres go.

Colin Robinson
2014-Feb-02, 03:02 AM
Because the water molecule forms non-covalent bondings. It is bipolar and easily "gets inbetween" other molecules which want to marry by charing their electrons more permanently. This makes water a great dating site where for example aminoacids quickly can try out their fit to many different parts of an RNA molecule. If they don't make good enough covalent bondings, water will immediately be there to separate them until the next one comes along for a try.

Methane (on Titan) is as liquid as water and does transport stuff around. But it lacks the ability to interfer with how other molecules bond. Biochemical processes would be much slower in methane liquid than in liquid water.

At present we know very little about what sort of dynamic systems could (or couldn't) emerge in a medium of liquid methane. I really don't think we know enough to determine with confidence how fast or slow things would happen.


There are other potentially liquid bipolar molecules than water, but since water is the second most common molecule in the universe, on Earth and inside all known living beings, it'd be a bit far fetched to search for such alternatives.

One molecule with strong polarity (stronger than water) is sulphuric acid, which is plentiful in the form of liquid droplets in the clouds of Venus. Venus, after all, is our nearest planetary neighbor, so the phrase "far fetched" hardly seems appropriate.

swampyankee
2014-Feb-02, 11:45 AM
Since this is all nearly-data-free speculation, and I like the number "3," I picked 3%.

It's certainly premature to say that there are no life-bearing moons in the Solar System, just as it's premature to say there are, although I think the latter is less likely.

Aristarchusinexile
2014-Feb-04, 04:39 PM
At present we know very little about what sort of dynamic systems could (or couldn't) emerge in a medium of liquid methane. I really don't think we know enough to determine with confidence how fast or slow things would happen.



One molecule with strong polarity (stronger than water) is sulphuric acid, which is plentiful in the form of liquid droplets in the clouds of Venus. Venus, after all, is our nearest planetary neighbor, so the phrase "far fetched" hardly seems appropriate.

Excellent!! Truly astounding that such speculation is allowed on a science forum!! And the dark shadows in the Venusian clouds are speculated to contain life. http://news.discovery.com/space/alien-life-exoplanets/are-venus-clouds-a-haven-for-life-130516.htmhttp://http://news.discovery.com/space/alien-life-exoplanets/are-venus-clouds-a-haven-for-life-130516.htm

Githyanki
2014-Feb-05, 11:46 PM
What about the radiation-belts from the gas-giant? Couldn't that kill life?

Noclevername
2014-Feb-06, 12:20 AM
What about the radiation-belts from the gas-giant? Couldn't that kill life?

For larger gas giants with metallic hydrogen, moon surface life would be in harms' way. Smaller planets like Neptune have far less magnetism and thus less radiation.

Also, ice-covered moons with internal oceans would have significant protection against radiation belts.