Expert: Tom Whiting - 12/28/2007

Question
QUESTION: is the asteroid belt really a 'belt' with a singular elliptical orbit or does it spherically house the inner planets?

ANSWER: Hi Daniel,
Well, it's certainly not fully spherical, but neither are they
all in one plane on the ecliptic.  Due to interactions over the
billions of years (4.6 billion to be exact), it's sort of torus
(doughnut) shaped.  Many of the main belt asteroids stray
only a few degrees from the ecliptic, like the major planets
did, but a small amount do have relatively high angles of
inclination, upwards of 30-40 degrees off the plane of
the ecliptic.  So it's really torus shaped, certainly not
spherical, so if our only one choice is available, I would
pick....in the plane of the ecliptic as that is closer to
the correct situation.  As far as the orbits themselves, just
like the major planets, they are all elliptical, and not
circular.  But each has it's own elliptical orbit, I don't believe
there is much "sharing" there due to past interactions.
Hope all this helps,
Clear Skies,
Tom Whiting
Erie, PA

---------- FOLLOW-UP ----------

QUESTION: Thank you. So apart form gravitational forces that seem to create an elliptical orbit, such as is found around Saturn, entry and exit form the inner planets can be achieved by going above or below the asteroid belt? Is this not recommended due to gravitational forces or is mankind only waiting for an adequate propulsion unit?

Answer
Hi Daniel,
I don't quite understand the question....mankind isn't "waiting" for anything.  We don't have to go "above or below"  the Main Belt Asteroid region, we go right through it, as evidenced by both Voyager missions, Galileo to Jupiter, Cassini to Saturn, and the current Horizons Mission to Pluto and beyond.  
You seem to be under the mistaken opinion that the Main Asteroid Belt is crowded, massive,  and dangerous....this is all science fiction baloney.  Due to it's huge size (volume), it is NOT the dangerous realm and picture that sci-fi writers have given you.

IN FACT, to photograph an asteroid on its way out to Jupiter,  Galileo had to go slightly out of it's way to even come relatively close to one asteroid just to photograph it at a large distance.  I think that's what you're getting at here,
but if not, then please re-word the question differently
and more succinctly.  There is absolutely no danger of
collision going right through the Main Asteroid Belt between
Mars and Jupiter, while staying right near the ecliptic.
In fact, you have to work very hard at trying to even get close to one asteroid, just for a simple long distance photograph!  There is just no sense, or no need,  in going "above or below" it....that's all science fiction.  We can travel
right through it, with no fears.

(The rings of Saturn are completely different...at that location, there WOULD be a fear of collision due to the high frequency of particles and chunks of ice, and boulders, in Saturn's ring structure, but it's only 100 yards thick, so there is a case where you would stay out of range, or go over or under, but that's not the consistancy and density of the Main Asteroid Belt.....by comparison, the Main Asteroid belt density would be like a child's small balloon, the size of a tennis ball,  floating around inside the Houston Astrodome.)

Oh, and if it's the total mass of the asteroid belt that you are
worried about, the combined mass of ALL the main belt
asteroids taken together is less than the mass of our own
moon.  But it's spread out so thin, that it's mass is barely
measureable, let alone catastrophic.  All spacecraft passing
"through" the asteroid belt, disregard it's mass because
it's so negligible, and evenly distributed.

Hope all this helps, but if not, feel free to re-word the question,
Clear skies,
Tom Whiting
Erie, PA