Re: Dirty Snowball Worlds

John Park wrote:

> Dave Farrance (DaveFarrance@[EMAIL PROTECTED]
) writes:
>> Logan Kearsley <chronosurfer@[EMAIL PROTECTED]
> wrote:
>> 
>> 
>>>World Idea #1: A tidelocked planet orbiting a red dwarf. The
>>>temperature goes above freezing at the substellar point, maybe leading
>>>to the formation of lakes or a small sea, otherwise just increased
>>>sublimation that keeps it relatively ice free. Question- do glaciers
>>>across the hemisphere creep towards the substellar point, or would it
>>>be more likely that the whole above-freezing region would remain ice-
>>>free, with mostly-static icesheets thickening as you get further away?
>>>Or something else entirely?
>>>Over on the dark side, temperatures get too cold even for the natives
>>>to find comfortable but there's no sunlight anyway, so it doesn't much
>>>matter. Perhaps there's a CO2 icecap around the antistellar point?
>> 
>> I don't know enough about planet formation to comment on World Idea #2,
>> but the problem with the above idea is that it will get *very* cold on
>> the darkside.  The entire atmosphere except for any helium would freeze
>> out.  The water would also eventually find its way around to the
darkside
>> via sublimation.
>> 
> Wouldn't that depend a bit on how thick the atmosphere was and how
> efficient its wind system was in moving energy around? (As far as I
know,
> despite its slow rotation--and because of its thick atmosphere--Venus
has
> no significant temperature difference between its day and night sides.)

It very much depends on the atmosphere's density and its composition.

You would have a "hot spot" which would shift with libration (precession?
as
well?).  This would create at least one atmospheric cell - in the form of
a
static cyclone.

How much it would affect the dark side would depend on the density of the
atmosphere and the composition, but it would act as a convection engine
moving heat to the cooler regions.  And moving moisture to the warmer
region.

The reason why such a system would die out would be the gradual loss of
greenhouse gases over a period of many thousands of years, or millions,
depending on their original partial pressure.  And matters such as
vulcanism, as has been pointed out, and the original depth of the
atmosphere, and other such details.  (I imagine that an Earth=1 depth
atmosphere would give a static cyclone at least up to the stratosphere,
and
to cool that down would take several hundred million years at least.)

But just my 0.02c

Wesley Parish
> 
> --John Park