On Feb 20, 9:27 am, Crown-Horned Snorkack <chornedsnork...@[EMAIL PROTECTED]
>
wrote:
> On 20 veebr, 09:17, Logan Kearsley <chronosur...@[EMAIL PROTECTED]
> wrote:
>
>
>
> > On Feb 19, 11:12 pm, Bryan Derksen <bryan.derk...@[EMAIL PROTECTED]
> wrote:
>
> > > Logan Kearsley wrote:
> > > > On Feb 18, 6:12 pm, Bryan Derksen <bryan.derk...@[EMAIL PROTECTED]
> wrote:
> > > >> If it is cold enough for CO2 to start freezing out on the
antistellar
> > > >> pole, then the atmosphere is already demonstrably not capable of
> > > >> sufficient heat transport thaw frozen CO2 back there.
>
> > > > It's demonstrably not capable of sufficient heat transport to thaw
> > > > frozen CO2 given not-necessarily-permanent current conditions.
That
> > > > doesn't mean it can't warm up again.
>
> > > No, but with CO2 absent from the atmosphere you'll have to warm it
up
> > > again via some mechanism other than greenhouse effect.
>
> > Well, obviously.
>
> Why? Why not greenhouse gases other than carbon dioxide?
>
> Like methane? Boiling point lower than that of carbon dioxide.
>
> Imagine... over time, methane concentration in atmosphere slowly
> increases, the general temperature rises... till the dark side gets
> warm enough to evaporate the carbon dioxide. Runaway greenhouse effect
> follows - first the carbon dioxide evaporates, then ice seats and
> oceans thaw.
Because they're not likely to be very common. If you start out with
lots of methane, the conditions for collapse will be much colder but
you probably won't accumulate very much CO2 (it will tend to be
destroyed in the reducing environment), and if you start out with lots
of CO2, the planet probably doesn't contain much methane (because it
will tend to be destroyed in the oxidizing environment), or suitable
stuff to make methane out of, barring biological activity.
Might be worth thinking about some other possibilities, though. Maybe
nitrous oxide could work in some special cases- if there's a thin
nitrogen atmosphere and high UV flux to break up water ice and let
hydrogen escape, you could eventually accumulate free oxygen which
would combine with the already-present nitrogen.
> (The cycle has a return side, too: once the oceans are open,
> photosynthetic production increases. Small quantities of free oxygen
> are released into atmosphere and the surface layer of ocean, while
> deep ocean remains anoxic and dead organic matter sediments there. The
> free oxygen rapidly removes the methane from atmosphere...)
-l.
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