Re: planetary and atmospheric rotation - origins, direction, etc

On Feb 27, 3:54=A0am, Tux Wonder-Dog <wes.par...@[EMAIL PROTECTED]
> wrote:

> Have there been any theses, studies, articles, etc, on this topic, the
> origin of planetary rotation and the direction of atmospheric
circulation?=


The atmospheric rotation is dominated by interaction with the planet
below (or in the gas of a jovian, the planet rotation *is* essentially
the atmospheric rotation at some scale), so I don't think you need to
think about those separately. The discussions below about frictionless
planets are interesting, but even for all-gas planets not relevant.

I remember reading a set of papers in Icarus long ago on a detailed
model calculation of the systemic and final random components to
planetary rotation, assuming realistic accretion models. The
conclusion was that the systemic accretion was thought to end up
producing a very weak prograde rotation, easily lost in the final
stages of accretion, and the obliquity of the planets would be
dominated by the final impacts. The calculated what size impactor
would have to have been responsible for the current obliquity of the
planets of all of that obliquity were due to a single final accretion
event, and came up with some surprising (to me) figures: Uranus could
have been "knocked on its side" by a single object with only 6% of
Uranus' mass (so an impactor of about 1 M_earth), while Saturn showed
evidence for a final impactor in the range of 3-10 M_earth. But all
this depended on the accretion model used as well, and that's still up
in the air to some extent. Take with a hefty grain of sodium chloride.

For large planets, even if the initial rotations are really weak,
you'd expect them to end up much faster due to conservation of angular
momentum and self-compression and contraction as they condense out of
the nebula, so the gas giant rotations aren't too surprising, while
the smaller gas giants and terrestrials should be a crap shoot.

--
Brian Davis