Re: Steam World


Mike Dworetsky kirjutas:
"Logan Kearsley" <chrono.surfer@xxxxxxxxxxx> wrote in message
news:Er70i.2945$vX4.2121@xxxxxxxxxxx
Say that a planet's oceans are boiled, but for whatever reason it does not
turn into a Venusoid inferno. Instead, you've just got an atmosphere full
of
steam, not too far from condensation, with little or no pure liquid water
on
the surface.

First question: how could that come about? Just start with very little
water, so the greenhouse doesn't run away too far? Somehow sequester CO2
so
that the temperature drops again when enough water is dissociated and lost
to space? Wikipedia tells me that carbonic acid is predicted to be stable
in
the gas phase- could that form naturally, and if so, would it allow for
the
formation of carbonate rocks to remove CO2 from the atmosphere, just as
liquid water does on Earth?


Sequestration on Earth takes place by CO2 dissolving in water and being
incorporated into rocks through limestone deposition and (if you have
shellfish) chalk. These need liquid water.

CO2 gets "baked out" of limestone through heating, so I am not sure if
sequestration in this scenario is possible at all.

But baking out requires a high temperature.

Second question: what liquids could exist on the surface, which could form
naturally? Sulphuric acid has a large liquid range, and concentrated
nitric
acid solutions boil at 120 degrees C- could small lakes of those liquids
occur? Anything else?

Acids tend to react with mineral bases on surface. I would suggest
salts and brines.

For example, imagine a runaway greenhouse on Mars. Let´s assume that
when the polar ice caps have melted and the readily available ground
ice also has melted - perhaps releasing giant floods, carving outflow
channels and pooling in lakes - the resulting lakes rapidly evaporate
away, giving Mars an atmosphere of a few tens of mb steam. With tghe
water vapour greenhouse effect, the temperature staying slightly over
boiling point, at, say, 40 or 50 degrees while pressure boiling point
is 20 or 30 degrees. The soluble mineral salts would form small
quantities of brines. There would not be much carbon dioxide
sequestration - because the brine quantities would be modest and
fresher water would not last long after outburst floods - but equally,
there would be little carbonate baking out at temperatures of just
40-50 Celsius. After all, no Venus-like hellish conditions was the
original assumption.

Plausible?

.

Relevant Pages

  • Re: Liquid lakes on Mars in the past
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