[meteorite-list] Tektites and Meteorites of Terrestrial Origin

From: Rob McCafferty <rob_mccafferty_at_meteoritecentral.com>
Date: Sun Jun 4 19:42:14 2006
Message-ID: <20060604175750.70078.qmail_at_web50914.mail.yahoo.com>

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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Received on Sun 04 Jun 2006 01:57:50 PM PDT