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

Eugen Leitl eugen at leitl.org
Fri Nov 22 11:56:12 UTC 2013


On Fri, Nov 22, 2013 at 12:04:15PM +0100, Tomaz Kristan wrote:
> We are talking about the situation inside *Galaxy*. And why the Earth (or

Not sure what's the point. Life doesn't emerge within stars or
even on insterstellar dust/ice grains.

> Solar system) is that different.

Local deviations can be arbitrarily high. There are carbon planets,
pure metal planets, what have you. Are they interesting? 
 
> Oxygen is the third with 1% of all the atoms. You can forget helium for its
> neutrality.

Still not see what you're looking at.
 
> http://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements
> 
> The top one and the third one - (forget the helium, it does not bond
> significantly) - love to join into water.
> 
> Our Galaxy must be very wet place.

Our galaxy is typical, and most of it is plasma. Molecules
are the exception rather than the rule.

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.



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