"fireballs virtually never hit the ground." Aren't bolides a fireballs too? And if so? Jerry Flaherty ----- Original Message ----- From: "Chris Peterson" <[EMAIL PROTECTED]> To: <meteorite-list@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: <[EMAIL PROTECTED]> > To: <meteorite-list@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 > > ______________________________________________ > Meteorite-list mailing list > Meteorite-list@meteoritecentral.com > http://six.pairlist.net/mailman/listinfo/meteorite-list ______________________________________________ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
