[meteorite-list] Tektites and Meteorites of Terrestrial Origin

[Rob McCafferty]

Very clever Doug.

Glad the new week is upon us as it means more think
time as I head off to work each new day. Can't do the
calculus in the car sadly and we don't get traffic
jams up here so I can't do it while the engine
overheats, either but I'll dig out the appropriate
stuff and do some scratching. 

I'd come to a similar conclusion to a lot of what
you'd said particularly the tektites having associated
craters but that doesn't always seem to be conclusive
as some, it is far from certain whther there are
craters. I'm willing to hedge my bets on that one
though. It's the fact that tektites look so different
from all the other achondrites that interests me and
some earth meteorites must look somewhat similar to
the parent rock. 

Yet, >11km/s impactor would probably, as you
suggested, have to retain most of this velocity to
stand a chance of removing a rock to space from the
surface through a hundred miles of atmosphere. As you
pointed out, what's going to be left of the earth rock
after all that?

Your reply does however assure me that my multitude of
meandering muses were not necessarily misguided. I
feared I  missed something blindingly obvious (as I
usually do).

I'll get to work whenever I can (AND my wife allows
me).

Thanks for the reply 

(Wasn't keen on the underground matress analogy
though. 15 rounds with Tyson, then if they survive,
make them do it again)

Regards

Rob McC

> Rob and  friends,
> 
> This is a hard question since it is in the Tounelan
> realm of  mullings: no 
> hard scientific evidence to study at the moment. 
> Thus it is  quite theoretical 
> to put it kindly.
> 
> First, I would think about how many  meteorites we
> have seen that retain any 
> cosmic velocity upon impacting the  earth's surface.
>  I would think carefully 
> about this as I lamented not  being able to listen
> to the eeriely classical 
> Finnish piece by Sibelius, the  Swan of Tounela, in
> my missing car stereo 
> comparing visions of the Swan  incessently circling
> to the possibility of myself 
> finding contemporary meteorite  fragments, as
> opposed to Lemminkainen's turning 
> sand into pearls as he hunted  down the innocent
> Swan.
> 
> After hunting the sacred and exquisite, dark 
> tektite-colored Swan, and 
> thinking I could have succeeded where the Gods have 
> failed, I would then be washed 
> up motionless upon the shores and wait for my 
> mother's vitreous celestial 
> tears to fall on my forehead to re-enbody my flesh 
> and spirit.
> 
> Earth's atmosphere's stresses are inverted vs. the
> meteorite,  for the 
> tektite's trajectory upon leaving the planet's
> surface.  We know  that meteorites 
> explode at shear frictional forces over 10
> kilometers high, so  we should expect 
> clearly at ground level a formation of a motley
> minutiae of  small fragments 
> of each and every candidate escape-bolder.  Upon
> breakup,  that fragment's 
> surface area to mass ratio changes drastically, and
> does it  surprise us that the 
> velocity is damped and the energy all converted into
> a bit  of fracture 
> energy and a lot of frictional energy (a favorite
> physics lab  experiment is to 
> shake a jar or sand abd measure the increase in
> temperature -  now imagine that 
> the friction is a stone wall of an atmosphere. 
> Inverting  the order of the 
> trajectory is like trying to catch a person from a
> very tall  burning building by 
> telling them to jump because you have put a bed
> several  meters under the 
> concrete that they will hit first...I wouldn't
> expect them to  survve that fall...
> 
> Later, I'd Google to find what percentage of the 
> surface of the earth was 
> silicated and look at the Nordlinger Ries crater
> source  rock and see if the 
> perceived absense of other minerals made sense given
> this  source rock.  Then I'd 
> look at the other tektites with proven  craters.  It
> should make sense or 
> else how would they have been linked  (source rock
> to tektite) in the first place?
> 
> On top of that, before  considering 'orbital
> dynamics' I would consider the 
> energy required for  achieving the threshold
> velocity to touch space from 
> Earth, even if it is only  to 100 km up, and then
> fall right back down.  I would do 
> it for a full  atmosphere of gas and thus need a
> handle on friction and 
> constrain my  calculations to time during which the
> glass remains plastic on the 
> way up - then  convert this energy for the gamut of
> tektite sizes and ask, now 
> does it make  sense that the temperature has to be
> so hot as to melt them  
> completely?
> 
> Then I would consider that the aerodynamic forms
> exhibited by  tektites 
> require it to have been a very fast and continuous
> event, since they  are found in 
> well defined strewn fields, and not randomly or at
> inconsistent  *large* 
> distances on Earth's surface.
> 
> I have no doubt the answer would be  yes for all
> these lame attempts to shed 
> some light on this.  Arguments for  plasma
> formation, reverse jets, while 
> founded, don't matter much for your  question, as
> the collision induced 
> temperatures and pressures for those specific  parts
> of the impact melt clearly wouldn't 
> produce contemporary meteoritesof the  type of the
> omnipresent 1000 on eBay.  
> Theoretically speaking, of course. I  haven't done
> the above calculations so 
> we stay on the comfortable level of  mullings.
> 
> Saludos, Doug  
> 
> 


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