On 22 veebr, 14:45, Tux Wonder-Dog <wes.par...@[EMAIL PROTECTED]
> wrote:
> Logan Kearsley wrote:
> > On Feb 21, 4:22 am, Tux Wonder-Dog <wes.par...@[EMAIL PROTECTED]
> wrote:
> >> 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.
>
> > As far as I can tell, libration wasn't included in the simulations.
>
> The study needs to be redone with it included, then.
>
>
>
> >> 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 ...
>
> > How much 'should' there be? It is what it is. I suspect that's a large
> > part of what's happening.
>
> Well, has anyone done an estimation/study of how long it would take for
a
> satellite to lose its angular velocity and become tidally locked?
>
> (I confess I have always tied the Coriolis Effect to the fact that
Earth's
> angular velocity isn't synchronous with its orbital period. I would be
> grateful for anyone to correct me on that.)
>
No. Coriolis Effect on Mars is completely unaffected by the fact that
Deimos is nearly synchronous. Rotating synchronously with orbital
movement of a more massive body would produce precisely the same
Coriolis Effect.
> > Or, an alternate explanation might be that I'm horribly
> > misinterpreting the graphs. I don't *think* I am, but I'll throw it
> > out there as a possibility, 'cuz the article never actually mentions
> > cyclones; one must infer them from the temperature and pressure plots.
>
> Is it possible that I could _see_ this article? > "Simulations of the
Atmospheres of
> > Synchronously Rotating Terrestrial Planets Orbiting M Dwarfs:
Conditions
> > for Atmospheric Collapse and the Implications for Habitability" by M.
M.
> > Joshi, R. M. Haberle and R. T. Reynolds
>
> I don't have it in my hot little hands, and I could only see the
abstract
> when I visited the web-site. My email address is wes [dot] parish [at]
> paradise [dot] net [dot] nz Thanks
>
>
>
> >> > 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.
>
> > I wrote imprecisely. By 'significantly', I was thinking 'several
> > orders of magnitude'; the period used in the article for a .1 solar
> > mass star was ~8 days. They actually did most of the simulations with
> > a .5 solar mass star and rotation rate similar to Titan, which is
> > about 16 days. But what if it were, say, 100 days? Does it make any
> > difference?
>
> Not that I can think of, right off hand. The only reason why it might
be
> significant that occurs to me, is the eccentricity of the orbit. If the
> orbit is nearly circular, the difference between the aphelion and
> perihelion won't amount to much; if it is highly eccentric, it won't be
> viable for Earth-standard life (or "life as we know it" ;) On the other
> hand, it might well prove the "breath of life" for your aliens - general
> overall torpor when the planet is at aphelion, time to party when the
> planet is at perihelion.
>
Earth-standard life handles several months of no Sun at all yearly -
in polar areas (mostly Arctic).
How would a planet look like with planetwide seasons due to
eccentricity rather than seasons opposing on opposite hemispheres due
to inclination as on Earth?
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