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fleas in the Cretaceous
Thank you, Paul Willis for correcting me on this p oint. I had
searched the literature and found no references at all to fleas
earlier than the Tertiary.
As for comets hitting Jupiter, I sh ould have made itd plain in
my book that I was refering to comets in orbit around the sun.
Once a comet or any o ther object has been captured by J upiter
it will make a large number of turns around J. If the cap ture
takes it inside the Roche limit at any point (3 planet diameters)
then the new orbit will slowly decay until it hits Jupiter, as
happened with Shoemaker-Levi-Shoemaker-9. By that time it
was a moonlet of J upiter, no longer a comet (if it every had been
one - and that is moot). The breaking apart into nine fragments
happened on a previous orbit when it came within the Roche
limit (well within it). This suggests a very fragile object,
and is the best evidence that it was a FORMER comet. The
apojovian on that orbit was less than one Jupiter radius out.
(If you don't know what an apojovian is think of apogee or
aphelion - the meaninng is the same with reference to Jupiter).
For comparison, the moon is currently about 40 earth radii out,
and started at something less than 30 (some people say 28). It
was never anywhere near the earth's Roche limit.
One stupid mistake in my book, if you haven't noticed it is
ascribing the names of the geological eras and periods to
Smith. Sowerby was the actu al namer of many of them. I
knew that perfectly well, but still wrote the wrong thing.
>From: David Brez Carlisle