[ExI] Double-Earth (Was: kepler study says 8.8e9 earthlike planets)

[Anders Sandberg]

On 2013-11-22 11:56, Eugen Leitl wrote:
> But for emergence of life, you will need molecules in a solvent, and 
> only water has a 4 C density anomaly. There might be transient uses of 
> cryogenic hydrocarbons, or water/ammonia and hydrogen disulfide, and 
> condensation from gas phase into solid state with subsequet 
> irradation, but for life you'll need a solvent, and it's almost 
> certainly always water.

I think we might be too hasty in ruling out other thalassogens.
https://en.wikipedia.org/wiki/Thalassogen
For rpg purposes I have been looking at exotic biochemistries, and I was 
surprised by the number of liquids that may exist in solar systems.
http://www.ifa.hawaii.edu/~meech/a281/handouts/Baines_astrobio04.pdf 
<http://www.ifa.hawaii.edu/%7Emeech/a281/handouts/Baines_astrobio04.pdf>

Water is perhaps the most abundant one, but one should not rule out 
ammonia - outside the ice line, especially if you get planets spiralling 
in from the colder parts, ammonia is very common. It can coexist with 
water in a lot of phases, and has a pretty interesting chemistry 
(dissolving and complexing with metals allows for some funky things). 
Methane and nitrogen are other options. While often dismissed as having 
too limited temperature range to be likely liquids, their range goes up 
a lot under pressure. Sulphuric acid, liquid hydrogen, and supercritical 
gases might be rare, but the more exotic solvents there are, the number 
of spots in the universe where life could exist goes up by a fairly 
sizeable factor.

Maybe ocean worlds, ice-capped seas or hothouses are dead ends from an 
intelligence or technology standpoint. But that still leaves plenty of 
weird options. We do not care much about what the majority of atoms do: 
it is the few spots that produce self-propagating formed integrities 
that really matter.

http://blog.practicalethics.ox.ac.uk/2013/11/invasion-from-the-blue-planet-are-we-protecting-mars-too-much/

-- 
Dr Anders Sandberg
Future of Humanity Institute
Oxford Martin School
Oxford University

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