🚀 go-pugleaf

In article <1k7arjINNhod@elroy.jpl.nasa.gov>, tjt@Jpl.Nasa.Gov (Tim Thompson) writes:
>    Joseph Cain asks if the fact that the Moon does not orbit in the plane of the
> Earth's equator is a clue to it's origin. Particularly, does this point toward
> the Moon being a captured object?
>
>    I think not. Most of Jupiter's tiny moons are certainly captured, 
> and they are
> nailed to Jupiter's equatorial plane (likewise Saturn, etc.). 

1) True only for the innermost ones, where tidal forces are large, and
the Galileans.  From Leda on out, they have inclinations of more than
15 degrees.  (Many are retrograde, but they aren't within 15 degrees
of 180.)

2) I don't know what perturbations make the Moon behave this way, but
Jupiter is *much* more oblate than the Earth (.0649 vs. .0034), which
would tidally crank inner moons toward the equator, and its
inclination to its orbit is lower (3.12 degrees vs. 23.45), so the
perturbing effect of the Sun to yank the satellites loose would be
low.

For Saturn, on the other hand, your facts seem to hold.

I knew there was a reason for keeping a table of planetary numbers
near my terminal!  Is there a place I can FTP this stuff so I can
stick it in my postings without typing all the values in myself?

> Timothy J. Thompson, Earth and Space Sciences Division, JPL.
> Assistant Administrator, Division Science Computing Network.
> Secretary, Los Angeles Astronomical Society.
> Member, BOD, Mount Wilson Observatory Association.

Oops.  Takes a lot of gall to argue with these credentials.  If Tim
proves me wrong, I will blame everyting in Beatty, Chaikin, and
O'Leary; I'm using the tables from *The New Solar System*.

Bill Higgins          |  If we can put a man on the Moon, why can't
Fermilab              |  we put a man on the Moon? -- Bill Engfer
higgins@fnal.fnal.gov |  If we can put a man on the Moon, why can't
higgins@fnal.Bitnet   |  we put a woman on the Moon? -- Bill Higgins