Water

[Gabriella]

Is it possible for an intelligent species to evolve on a planet with absolutely no water? I emphasize intelligent species because obviously you can have some forms of life without water.

[Turtle]

___Welcome to the Hypography Forum. I can' think of any life we know of that doesn't require water; what did you have in mind?

[Gabriella]

Just wondering if anyone thinks it's possible. I wonder what the species would be like if it is.

[Fishteacher73]

Well assuming that life can evolve w/o water (although we really don't know how it would would work) it would be very unlikely that it would resemble humans in much of any way. We are a result of natural selection provided by not only the environment, but the other species we interact with. Any system based on completely different chemistry would no doubt have very different species (not to mention the greatly varying abiotic factors that would exist in a non-water environment). Just look at the variances between desert species and marine species..(and thats just a little less water).

[Little Bang]

I would think that life could evolve in any liquid medium that could dissolve compounds, and given life the possibility of intelligence must also exist. A prerequisite for intellect may be a prehensile appendage, because if you can't manipulate small objects I don't think the need for intellect would ever occur.

[UncleAl]

Aqueous systems are the only ones that support sufficient chemical complexity at reasonable temperatures and oxidizing conditions to bring forth life, much less intelligent life. Liquid ammonia has a vast chemistry, but its low temperature is detrimental to chemical kinetics and it requires an overall reducing planet. Odd-Z nuclei (nitrogen) are not as abundant as even-Z nuclei (aside from hydrogen; oxygen). Saturn's moon Titan, interesting for its supposed vast oceans of methane and ammonia, turned out to be a blob of damp mud. Not much ammonia, either.

It would be interesting to do the Urey, Miller, Ponnamperuma, abiogenesis experiment with -33 C liquid ammonia, methane, hydrogen sulfide, phosphine, water, and electric discharge. If there is no accumulation of a vast inventory of organics and their conversion (after a week or two) into coacervate droplets... that tells you a lot. You could do it at higher pressures to extend ammonia's liqud phase to ambient temperatures, past 100 C if you like. It would be an interesting experiment to see how versatile star tar was under non-terrestrial conditions.

[alxian]

some people say alcohol, some people say some gases in the right environments and pressures (gas giants), maybe even very powerful magnetic feilds.

i'd like to think its as simple as there being enough potential for energy conversion within a system, as well as chemicals for storing information like dna which requires at least in our evolution acids of all sorts, either just chemically or through such systems as catalysing solar radiation with gases and liquids, also a good argument for life in the higher atmospheres of gas giants.

a funny thing is all the planets we find that are gas giants right up close to their stars, they would be good breading ground for life if the temperatures weren't too hot, or the planets spin to high or slow.

but the question is can intelligent tool using, writing, social animal develop in floating environments like clouds or oceans. it's likely that we developed as we did as a direct result to having adapted to several environments, land, sea, air, low oxygen concentrations, sea level, we've adapted to them all and are more powerful because of those adaptations. without different environments their is less likelyhood that a creature will continue to evolve past a point where they can survive comfortably.

[Boerseun]

If you look at the crazy mix of life on Earth, from gut-infesting flatworms to Third-World dictators (same species) to jellyfish to self-illuminating deep-sea organisms, all the way up to homo sapiens sapiens, I don't think we'll meet any extraterrestrial species any stranger than those currently living on Earth. A squid is pretty weird. Period.

Whether they'll be H2O dependent is another matter completely. As far as I can see, they need some usable solvent system to keep them going. On Earth, water is the key. But then again, Earth is a water planet. Life on gas giants like Jupiter and Saturn have been conjectured to be the likes of gigantic gas-filled bags floating, foraging and hunting in the dense atmosphere. That'll probably be ammonia-based.

I honestly don't know - but I think we're using water at the temperatures we do because that's the prevalent conditions found on Earth.

[Qfwfq]

Originally Posted by Boerseun

all the way up to homo sapiens sapiens

Up??? Can we be quite sure of that?

[HydrogenBond]

The essense of the living state is hydrogen bonding. Without hydrogen bonding the DNA double helix and all the template relationships would not form. Water is a hydrogen bonding solvent and medium for cellular hydrogen bonding. Ammonia could almost do the same thing because it also forms hydrogen bonds, NH3. The problem is that ammonia becomes a liquid at -33C. Reaction kinetics would stall. The answer is, water is needed.