[FoRK] Water != Life (other solvents may work too)

damien morton fork at bitfurnace.com
Mon Jan 31 09:39:40 PST 2005

Eugen Leitl wrote:
> On Sun, Jan 30, 2005 at 10:02:00PM -0500, damien morton wrote:
>>Even the notion that you need chemistry for life is suspect.
> Are we talking naturally emerged, or designed? Designed indeed doesn't
> require chemistry, see ALife.

Greg Egan wrote a lovely short story about an emergent 'ALife' that 
existed 'inside' a substrate formed by the plants on an ocean planet, 
whose movement and grouping behavior was individually simple, but as a 
whole formed a computing substrate capable of supporting ALife.

Fanciful, perhaps, but I have a feeling that the definition of life will 
  eventually have to be stretched to include such.

>>In my mind, all thats needed is a substrate that supports enogh compelxity.
> For natural processes, we seem to be stuck to condensed phase.
> Gas and plasma doesn't support persistent structures. There might be life
> based on strange/dark matter, but we currently have no evidence that's
> possible.

Thats not true. Gas certainly supports persistent structures, for 
example, clouds. cf 100-year old storms on the face of jupiter. As to 
whether gas supports structures capable of life, I dont know, but it 
likely depends on what you define as life.

>>Theres probably all kinds of environemts where that can happen.
> Not really, natural element abundancy is basically the same across the
> universe (local variation in metallicity currently favor the light regime),
> so there are not many solvents available.

Assuming, that life depends on chemistry.

> You need polar solvents, so liquid hydrocarbons are right out. This leaves
> you with water, ammonia and *maybe* hydrogen sulfide. Water is special
> because of 4 C anomaly, and wide liquid range (look up the phase diagram of
> its close cousins, the difference is dramatic). Also, rate of chemistry at low
> temperatures is glacially slow (Arrhenius equation).
> Titan is certainly interesting inasmuch prebiotic chemistry is concerned. It
> might even have life in its volcanic hot spots (relatively hot, liquid water
> lava is pretty balmy). But, I think Europa has a far better chance of bearing
> primitive life. Notice Europa would be barren, if its oceans were liquid
> ammonia. Earth would be also likely barren, or only bear primitive life if it
> wasn't for the water anomaly.
>>Greg Egan is the sci-fi writer who explores this best (IMO).
> Greg Egan's physics is frequently b0rken.

Your spelling appears to be brok3d.

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