Mime-Version: 1.0
Date: Wed, 18 Jun 1997 11:01:14 -0500
To: "Anthony C. Zuppero"
From: "John J. Matese"
Subject: Re: comet hole, lunar ice rocket
Cc: pgwhitman@usl.edu
Hello Tony,
I found a few hours to think about your comet hole problem. As I
understand it, the question essentially can be phrased as
"Is the hole due to (1)dynamics unrelated to the inner planets,
(2)disappearance due to devolitization or breakup,
(3)dynamics related to the inner planets?"
Of the three options listed my gut feeling is that they rank in
importance in that order, with all contributing to some extent. Brian
Marsden's comments might in part be paraphrased in the following way.
Jupiter family SP comets are often discussed in terms of their Tisserand
parameter, essentially the Jacobi constant of a restricted three body
problem. Scaling distances to Jupiter's semimajor axis, a comet of
semimajor axis a(scaled), eccentricity e, inclination i has a Tisserand
parameter
T = 1/a +2 sqrt[a(1-e^2)] cosine(i)
One can show that if T>3 Jupiter crossing is impossible. Most comets
have 2.5
So, in this view, the clustering of T near 3 (which causes a deficiency
of comets with small q) could be due to the dynamical mechanism by which JF
comets are assumed to be produced - from the Kuiper belt via transfer
between the giant planets.
Of course one must always keep an open mind that the reverse could be
true, i.e., mechanisms (2) and (3) above create a deficiency of small q
JF comets -> T clustering near 3 -> we are fooled into thinking that the
Kuiper belt is the source. That is very ad hoc and would be difficult to
defend.
I hope this helps.
Best regards
John J. Matese Professor of Physics
matese@usl.edu The University of Southwestern Louisiana
Lafayette, Louisiana (USA)