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re: (meteorobs) Re: Rocks from space...
>Thanks for your response, Wayne, and thanks for the info related to
>velocities and time of atmospheric travel.
No problem
>Is it possible that a very
>large object from space could travel very slowly and thus achieve
>conditions more favorable for heat transfer to the meteorite center?
>What's all this about "minimum velocity"?
Pure and simple Gravity. An object falling to the earth from space
will accelerate at 32 ft/ sec/sec. (To mix units Ha Ha) leading to a
minimum speed at contact with the atmosphere (100-125 km up) of 11 kps.
This assumes that the object has almost zero velocity relative to the
earth.
Maximum velocity is (approximate #'s) 30 kps of earth's motion around the
sun, running head on into material moving at the maximum velocity for an
object in orbit around the sun at 1 AU (42 kps), plus the added
acceleration due to gravity (~ 1 kps) at these speeds. The Leonids are
close to this speed.(It gets here so fast it has not much time to
accelerate, the opposite of the slowest possible object where the
acceleration is almost entirely due to gravity)
>Also, with regard to the above
>comment, just what exactly do you mean by "more substantial material"?
>I'd
>like to know about meteorite composition in terms of minerals, elements,
>etc. Any suggestions for good, technical books to read on the subject?
>How about technical journal publications?
I don't have a good list of these yet. I know George has mentioned a book
or two, and I'm sure others will have good suggestions. I have some lists
at home which I'll post later when I dig them out of the "library-pile".
Simply, most meteor shower meteors are comet dust; low density friable
material.
Most meteorites that reach the ground are derived from asteroids, hence a
dense mixture of various proportions of rock, iron, and nickel. There are
several different common mixtures which seem to be derived from particular
asteroids both known and unknown, as well as some from the moon, and some
from Mars.
Specifics will have to wait till I find some of my books and journal
papers at home.
Wayne
Thanks, Keith.
Keith C. Evanson
Ph.D. Candidate and Graduate Research Assistant to Dr. George Krauss
Advanced Steel Processing and Products Research Center
Metallurgical and Materials Engineering Department
Colorado School of Mines
Golden, Colorado, USA
80401
work phone: (303)273-3708
num. pager: (303)259-7548 ***preferred business contact method***
fax number: (303)273-3795
email: kevanson@minesdot edu
web: http://magma.minesdot edu/students/k/kevanson