[meteorite-list] meteoroid question

[Pat Brown]

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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