Keep in mind during any analysis that small meteoroids are not in stable
orbits, and do not persist forever in the Solar System. There are drag
processes that produce a continual inflow of small objects towards (and
ultimately into) the Sun, and small objects (especially in planet crossing
orbits) are continually being perturbed. A meteoroid that grazes a planet's
atmosphere and receives a fusion crust probably has a lifetime measured in
millions of years at most, and often much less. So you need to consider both
the production and destruction rate of fusion-crusted meteoroids.
Also, I don't know that talking about absolute numbers is particularly
useful. Whether that number turns out to be large or small, it certainly
represents a vanishingly small percentage of the total meteoroid population.
You're very unlikely while in space to encounter any meteoroids at all; it
could take a ridiculously long time to find one that had previously
encountered a planet.
Chris
*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
----- Original Message -----
From: "Meteorites USA" <[email protected]>
To: <[email protected]>
Sent: Wednesday, March 25, 2009 11:52 AM
Subject: Re: [meteorite-list] Fusion Crusted "Meteoroids"
Anyone remember this one? ;)
THE GREAT DAYLIGHT FIREBALL OF 1972
This grazing of our atmosphere would cause fusion crust. This means that
the Great Fireball is a meteoroid with fusion crust.
Over Jackson Wyoming: http://www.youtube.com/watch?v=It5EztnIdHc
Over Canada: http://www.youtube.com/watch?v=AaxagBP0IoY
http://apod.nasa.gov/apod/ap090302.html
http://en.wikipedia.org/wiki/The_Great_Daylight_1972_Fireball
Earth Grazing Asteroids (PDF):
http://www.lpi.usra.edu/meetings/lpsc1994/pdf/1142.pdf
Fusion Crusted Meteoroids.
The video shows a great example of it and science knows that this happens.
How often it happens and how many are there is the question? If this
happens once every 10,000 years (hypothetical) then that would mean there
may be hundreds of thousands if not millions of them out there.
---------------------------
1 Every 10,000 years
100 Every 1 Million years
1000 Every 10 Million Years
10,000 Every 1 Hundred Million Years
100,000 Every 1 Billion Years
---------------------------
That's if you count just Earth. There are 7 other planets out there not
counting Pluto. Keeping in mind the likelyhood of a meteoroid crossing
the orbit of a planet at a shallow enough angle, are Neptune's, Uranus'
and Saturn's, Jupiter's, Mars', Venus', and Mercury's atomospheres thick
enough to bounce a meteoroid off of and create fusion crust? And if so
could we safely say that there's hundreds of thousands if not millions of
fusion crusted meteoroids and asteroids out there floating around? I would
venture to "guess" that it might happen a bit more than once every 10,000
years. The odds are good that it happens far more often. Think about it
for a second. What's the likelyhood that it would be caught on tape if it
happened only once every ten thousand years? We see daylight fireballs
many times per year, how many of those are Earth-Grazing meteoroids or
asteroids and never burn up completely?
Can we agree that 70% of the meteorites that actually strike Earth land in
the oceans since water covers 70% of the planet. Furthermore, since we
only occupy a small percentage of available land mass then that leaves a
HUGE amount of land that is either uninhabited or inhabited by native
peoples that have no contact with the outside world. Meaning that any
meteor fireball that passes over or impacts in these areas are NOT ever
reported. I know we can make educated guesses about how many times this
might happen based on observations from many points on our planet that we
actually occupy.
Isn't there hard data out there on these types of actual Earth-Grazing
meteoroids and asteroids? The ones that actually enter our atmosphere and
then leave to go flying back out into our solar system. Based on that data
couldn't you make "an educated guess"? Can't we take data from these
events and figure the time between them and estimate a number, then divide
that number into say 4.5 billion years? (If you figure the Earth and solar
system is that old, which by the way is a guess too, albeit an educated
one) I'm sure there will be people to argue this point to the end of time.
Still think there aren't many fusion crusted meteoroids out there?
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