Neal McBurnett scripsit:
> > I wouldn't be too quick to dismiss tidal braking from Phobos. It's
> > awfully close to Mars, and tidal braking is as you say an inverse-cube
> > effect. The formula (kai Wikipedia) is (2GMmr)/R^3, where M and m are
> > the masses, r is the radius of the primary, and R is the orbital radius
> > of the secondary. The mass of the Earth-Moon system is eight orders of
> > magnitude larger than the Mars-Phobos system, and the radius of Earth
>
> I assume you mean the mass of phobos vs the mass of the moon, not the
> systems, since that is what fits in the raw numbers and equations you
> provide. But that is less than 7 orders of magnitude different, as I
> read your reference.
Actually I didn't mean either one: I meant the mass of the primary times
(not plus) the mass of the secondary, the "Mm" in the formula. So
the mass of Mars times the mass of the Phobos is ~ 10^39 kg, whereas
the mass of Earth times the mass of the Moon is ~ 10^47 kg: eight
orders of magnitude, as I said. Sorry for the misstatement.
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Received on Wed Jan 11 2006 - 23:45:56 PST