[meteorite-list] Fusion Crusted "Meteoroids"

[Chris Peterson]

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" <eric at meteoritesusa.com>
To: <meteorite-list at meteoritecentral.com>
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?