[meteorite-list] meteoroid question

From: cdtucson at cox.net <cdtucson_at_meteoritecentral.com>
Date: Mon, 5 Oct 2009 11:52:25 -0700
Message-ID: <20091005145225.F4L7O.489755.imail_at_fed1rmwml40>

List,
Sorry, but it is difficult to measure a negative!
There is simply no way of knowing what the size of a meteorite you are holding in your hand was before it entered the earths atmosphere. Period.
In order to figure out what the bulk of a meteor was prior to entry you would need a crystal ball.
This is said with all due respect to our scientific community but there are simply too many unknowns for this question to be properly answered..
First you would have to know the exact weight prior to entry. Then weigh the meteorite and do the math.
I am not aware of any natural fall that the weight of such fall was measured prior to entry into earths atmosphere.
The only scenario that even comes close was the Stone-6 artificial meteorite mission.

http://euro.astrobio.net/pressrelease/2889/stone-6-microbes-0

This study did prove ablation occurs but, it has been pointed out on this list that that study was full of flaws and holes and not a good judge of reality.
Again, It did prove that there is loss of material caused by friction or ablation and actually some of the samples disappeared completely.
It is true that Tagish lake is very fragile but no meteorite I have ever seen is as fragile as Carancas. This material can easily be crumbled between your fingers. Yet, it managed to get through our atmosphere and leave quite an impressive hole in the ground. It has been noted that due to this fact. All past theories are now out the window. Carancas has literally caused the books to need to be re-written when it comes to the whole entry ablation theories.

http://www.geotimes.org/july08/article.html?id=feature_meteorite.html

" Final Findings
The meteorite impact at Carancas was a lucky surprise for scientists. It is not clear how a chondrite, a relatively weak rock, traveling at least at four times the speed of sound, was able to survive passage through Earth?s atmosphere intact and impact the planet, but it did."

This is not my sole opinion. This fact has been stated in many previously written scientific papers. Like Elton always says; "don't ignore the science"
In summary, I think it is safe to say that meteorites start out bigger before we found them laying on the surface of Earth. How much bigger is just a guess.

--
Carl or Debbie Esparza
Meteoritemax
---- Pat Brown <scientificlifestyle at hotmail.com> wrote: 
> 
> Hello Larry and the List, 
> 
> This is an interesting and very commonly asked question that I have been asked in talks to school kids etc. I have tried to make it through Opik _Physics of Meteor Flight in the Atmosphere_. However, it is far too easy to get bogged down in the math. 
> 
> OK, that said; this engineer's guess is 
> 
> * An incoming velocity range of 15,000 to 25,000 gives an kinetic energy range of 2.8:1
> 
> * The entry angle could affect the time of incandescent flight as well. The ratio of 90 deg to almost zero deg could be a 2:1 ratio as well
> 
> * Even if we limit ourselves to Chondrites, and assumed a constant speed and entry angle, the range of internal strength of the material is an important part of the answer. I tell the kids that the range of strength of the stone meteorites  ranges from almost dirt clod weak (e.g. Bjurbole, Tagish Lake) where the survival percentage is perhaps 99% of mass loss. At the other end is a strong ordinary chondrite without internal cracks and little or no shock that could be in the 50% mass loss range. As an average, I have been telling the kids that basketball in space equils softball size when it reaches the surface. [For our international friends a basket ball is 0.74 meters in circumference and a softball is 0.30 meters in circumference.]
> 
> Please do let us know what you get for answers from Rob Matson and the rest of the List. 
> 
> Best Regards, 
> ?????????? Pat Brown
> 
> ----------------------------------------
> > Date: Sun, 4 Oct 2009 19:51:55 -0700
> > From: lebofsky at lpl.arizona.edu
> > To: Meteorite-list at meteoritecentral.com
> > Subject: [meteorite-list] meteoroid question
> >
> > Hi all:
> >
> > I am involved with a teacher professional development workshop this week
> > and the teachers give us questions that they hope we can answer for them.
> > I am fine with most of them (such is Pluto a planet?), but I figured that,
> > before I give them a partially correct answer, I would ask the experts out
> > there for their responses:
> >
> > What is the rate at which things burn up when they enter Earth?s atmosphere?
> >
> > About how much material is burned up (mass per unit time)?
> >
> > Along that same idea, for a "typical" chondritic meteoroid, what is the
> > minimum size that you might expect to make it through the atmosphere and
> > land as a meteorite? Ballpark is fine since, clearly there are many
> > factors involved (initial velocity, angle of entry, material strength
> > etc.).
> >
> > Thanks in advance.
> >
> > Larry
> >
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Received on Mon 05 Oct 2009 02:52:25 PM PDT