[meteorite-list] ANOTHER QUESTION

[Gerald Flaherty]

"fireballs virtually never hit the ground."
Aren't bolides a fireballs too? And if so?
Jerry Flaherty
----- Original Message ----- 
From: "Chris Peterson" <clp at alumni.caltech.edu>
To: <meteorite-list at meteoritecentral.com>
Sent: Sunday, November 19, 2006 6:29 PM
Subject: Re: [meteorite-list] ANOTHER QUESTION


> Technically, fireballs virtually never hit the ground. But assuming that 
> you mean fireballs produce meteorites, even that is hard to quantify. We 
> assume, based on calculation and observation that many, or even most, 
> meteorites fragmented from meteors bright enough to be called fireballs. 
> But that doesn't mean most fireballs produce meteorites.
> 
> It is generally thought that in order to produce meteorites, meteors 
> need to be slow and shallow. Also, they need to be large enough and 
> sturdy enough that some material survives. Generally, meteorites 
> represent only a tiny fraction of the original mass.
> 
> Different showers produce fireballs for different reasons. Leonids and 
> Perseids are high velocity. When the particles are large (say, pea 
> sized), they dissipate a lot of energy at high altitude. This means they 
> burn up completely. Other showers, like the Geminids, are low velocity. 
> Larger pieced can survive somewhat lower, and burn in denser air, for 
> longer times. That's why Geminid trails tend to be longer than Leonid 
> trails. But aside from questions about the material strength of shower 
> material (assumed, but without much evidence, to be weak), most of the 
> material is just too small to survive. It burns completely before it 
> slows down enough to cool, and drop. There probably isn't much up there 
> the size of basketballs, or even baseballs. I imagine comets produce 
> some larger pieces like that, but they would only represent a tiny 
> fraction of the total. It might be years between Earth collisions with 
> such large pieces.
> 
> Chris
> 
> *****************************************
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
> 
> 
> ----- Original Message ----- 
> From: <jwb7772 at netzero.net>
> To: <meteorite-list at meteoritecentral.com>
> Sent: Thursday, November 16, 2006 4:26 PM
> Subject: [meteorite-list] ANOTHER QUESTION
> 
> 
> Hi All!
>     I have another question concerning meteor showers.  That is-----If 
> showers do not produce meteorites, then how come fire balls are often 
> seen during the Perseid's?  Fireballs often hit the ground providing 
> that they do not blow up.  I believe that Temple replenished the field 
> not too long ago so there has to be a lot of bigger rocks up there.  Yes 
> most are just dust, rice sized grains and pea sized rocks but I like to 
> think that base ball, foot ball, and basket ball sized rocks are just 
> lurking around and just waiting for us to look up and watch them come 
> screaming down in a blaze of glory!  Jim Balister
> 
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