Re: Dirty Snowball Worlds

Logan Kearsley wrote:

On Feb 20, 3:39 am, Tux Wonder-Dog <wes.par...@xxxxxxxxxxxxxxx> wrote:
John Park wrote:
Dave Farrance (DaveFarra...@xxxxxxxxxxxxxxxxxxxxxxxxxx) writes:
Logan Kearsley <chronosur...@xxxxxxxxx> 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.

.

Relevant Pages

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