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Is water really necessary for extraterrestrial life?

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DeaconBlues
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17 Jul 2010, 9:08 pm

While it is theoretically possible for life to possess a different basis than carbon, it's a simple chemical fact that of all the possible bases, carbon forms long-chain molecules more easily, and with more other elements, than any other basis. Carbon-based long-chain molecules are also more resistant to destruction by radiation than others. This in part explains why we are finding organic matter (that is, matter composed of long-carbon-chain molecules) in the outer solar system, and signatures indicative of organic molecules in interstellar gas clouds (for instance, one of the major components of the famed Eagle Nebula would appear to be alcohol).

Assuming that the life forms are carbon-based (which is indeed an assumption - we have only one data point from which to draw information), said life would require water to survive. It might not be much water - there are microbial life forms in our driest deserts - but it does require some amount of water.

As for intelligent extraterrestrials, if they weren't carbon-based, they probably wouldn't even bother with this planet - to a silicate life form, for instance, the water and free oxygen on this world would prove instantly deadly, and they probably wouldn't even take the time to check such an "obviously" lethal world for life...


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ruveyn
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18 Jul 2010, 3:33 am

nodice1996 wrote:

Also, Ruveyn, who says all life is carbon based.


I never said that. I said water was necessary to carbon based life.

I did not say a thing about non-carbon based life.

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18 Jul 2010, 9:20 am

nodice1996 wrote:
Peko wrote:
Maybe as all life on Earth is made up of water in some form, it seems to be the most logical assumption/hypothesis. I really don't know the answer, but I think ice caps of some kind were also found on our moon and Mars at least (which is why some think life may/have been on Mars). Also, water had special qualities that other liquids and compounds do not have (that I am aware of), such as having a solid, liquid and gaseous form (all 3) and some other stuff I cannot think of. But if their was another special compound like water that could have all 3 solid/liquid/gas forms & such, I don't see why it could not support life.

Only Mars has Ice caps, it also has evidence of liquid water, such as eroded rivers and such.

Also, Ruveyn, who says all life is carbon based.


Looks like the moon has water
http://www.nytimes.com/2009/11/14/science/14moon.html


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18 Jul 2010, 9:36 am

Peko wrote:
Maybe as all life on Earth is made up of water in some form, it seems to be the most logical assumption/hypothesis. I really don't know the answer, but I think ice caps of some kind were also found on our moon and Mars at least (which is why some think life may/have been on Mars). Also, water had special qualities that other liquids and compounds do not have (that I am aware of), such as having a solid, liquid and gaseous form (all 3) and some other stuff I cannot think of. But if their was another special compound like water that could have all 3 solid/liquid/gas forms & such, I don't see why it could not support life.

What? All substances have solid, liquid, and gaseous forms.

Water is special largely for its polarity.


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zer0netgain
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19 Jul 2010, 6:41 am

For life as WE know it, water is essential. So, if we want to find another world with life similar to ours, certainly life-sustaining for us to live there, water is essential.

Life, however, is very adaptable and can exist absent water, but it would indeed be very alien to our own biology.



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19 Jul 2010, 7:59 pm

Water in a frozen state floats on liquid water. A creature in a pond of some other liquid would need to worry when it get cold. The liquid would freeze and sink to the bottom, eventually leaving no space for the creature.

Hydrogen Sulfide metabolators inhabit deep ocean vents near the Galapagos islands. They are dependent on bacteria to metabolate the hydrogen sulfide.

Methane is used on earth. The substance forms a kind of ocean within an ocean, an creatures have been observed metaboalting that as well.



Peko
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20 Jul 2010, 10:46 am

Orwell wrote:
What? All substances have solid, liquid, and gaseous forms.

Water is special largely for its polarity.


Polarity is the world I forgot *facepalm*
Orwell: you probably noticed that when I posted the first time I was having an off brain day :wink: :roll:


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ruveyn
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21 Jul 2010, 4:59 pm

water is necessary for terrestrial life.

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03 Aug 2010, 1:03 pm

nobody, i think, went farther than V A Firsoff in his discussion of other chemicals than hydrogen oxide (Life Beyond the Earth 1963). he finds a solvent or two for every temperature range from -300 C to 300+...

like, mercury dibromide

in fiction, of course, Hal Clement wasn't afraid to go there.

m.