Re: Dirty Snowball Worlds

Logan Kearsley wrote:

> On Feb 20, 3:39 am, Tux Wonder-Dog <wes.par...@[EMAIL PROTECTED]
> wrote:
>> John Park wrote:
>> > Dave Farrance (DaveFarra...@[EMAIL PROTECTED]
) writes:
>> >> Logan Kearsley <chronosur...@[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.
> 
> I have never had this adequately explained- some of the simulations
> result in two cyclones, mirrored across the equator, and others result
> in a single cyclone. In the single cyclone case, what determines the
> direction of rotation?

I think it would be the libration that would determine the direction of
rotation.  It'd be heating an area that would shift within a few degree
per
orbit, and the effect would be the same as swinging a stone on the end of
a
string.

Could someone who knows a bit more than I do, explain the two cyclone
concept?  The only reason I can think of why there would be two cyclones
is
that there is still more rotation in the system than should be in a
tide-locked planet.  And thus there is still a north/south-hemisphere
atmosphere ...

> And what happens when the planet's rotational period is significantly
> longer than 24 hours?

The planet is tidally locked.  If its rotational period was 24 hours long,
it would be very close to its sun - I suspect almost within its
photosphere.  And no star has its ecosphere/Goldilocks zone that close. 
By
definition its rotational period is longer than 24 hours.

Wesley Parish
> 
> -l.