Sterling,
Fabulous exposition! That one cost me some more
printer ink. I do have a few questions and comments.
No trace of terrestrial material? I'm not sure I
understand. If you mean no embedded clasts from the
target surface, I agree. That is very odd,
considering the obvious plastic deformation of the
splatforms. But if you are talking composition, the
elemental and isotopic mix is (reportedly) quite
terrestrial looking. I'm not sure what else one could
hope for.
No matter where they came from, some should've skipped
around on top of the atmosphere and made their final
entry far from the main bulk of the fall. You have
cited some really interesting examples. Does your
emphasis on antipodal points have particular
significance? For example, if an object narrowly
misses re-entry angles is the next best shot
antipodal?
I am not at all content with the volume estimates for
the North American (Georgiaite/Bediasite) strewn
field. Since we can only see the eroded edges of the
host strata, our perspective is very limited. The
total recovered mass is trivial. Some monstrous
assumptions are involved in the oft-quoted estimates.
While on the subject of the North American tektites,
one of my favorite questions is why there is such a
marked difference between Georgiaites and Bediasites?
Some argue for melts sourced at different depths (and
target compositions) in the source crater, but this
doesn't strike a full chord with me.
Regarding Rayleigh Taylor instability, you are way
beyond me. But if I understand you (a little), part
of the problem is the lack of apparent mixing of the
target and impactor materials. I have never heard of
this lack. Tiny Ni-Fe beads are reported in a variety
of meteorites, and I have always believed (without
proof) that the inky blackness of all but the
moldavites might well be due to integration of
impactor Fe.
Your discussion involving the missing Australasian
crater is excellent. This thing cannot be easily
hidden. We should be able to still hear the earth
ringing with reverbrations. This is a huge problem.
I am also perplexed by the objects that I term
splatforms---tektites that have clearly splatted
while still significantly plastic. How far can a blob
of molten glass travel before it cools sufficiently
that it can no longer splat? tens of kilometers?
hundreds? Splatforms are found from south China
through Laos, Thailand, Vietnam---and of the
Tibetanites are real, Tibet. A huge area. Exactly
the same thing can be said for Muong Nongs. Same
areal distribution, no evidence of flight.
Further, if you want a full kilo specimen, you'll have
to go to the Philippines. The big ones flew a long
ways---but NOT to the far end of the strewn fiel like
most meteorites. Most Australites are relatively
tiny.
Antarctica. Not a small point by any means. Where
are the tektites?
Good stuff. Keep on ruminating!
Cheers,
Norm
http://taktitesource.com
--- Sterling K. Webb [EMAIL PROTECTED] wrote:
Hi,
Hey! If Rob says he can't figure out a way
to get tektites
shipped in from the Moon, it's good enough for
me, But then, I
never thought they came from the Moon. The
lunar origin theory
is an old one. In fact, all of the 40-odd
theories of the origin
of tektites are old (and most of them are odd,
too).
It might surprise meteorite fanciers to
know that the
argument over tektites goes back to the time
when meteorites were
still regarded as a myth or of being formed by
thunder! The
first speculation about tektite origins dates
from 1793, more
than a decade before the French Academy was
persuaded by the
L'Aigle fall that rocks really did fall from
the sky.
To those with long memories, I will recall
to them the late
List member Darryl Futrell, who supported the
lunar origin
theory, more from geological evidence than
orbital
considerations. I corresponded a lot with
Darryl and I believe
he did so more out of loyalty to the late John
O'Keefe than being
really convinced by the theory.
Take a look at:
http://six.pairlist.net/pipermail/meteorite-list/2001-May/024512.html
http://six.pairlist.net/pipermail/meteorite-list/2001-May/024513.html
http://six.pairlist.net/pipermail/meteorite-list/2001-March/022903.html
The current orthodox theory of tektite
origin is the impact
theory: that tektites are modified terrestrial
surface rocks,
modified by impact into molten drops, ejected
into orbits above
the atmosphere where they are rapidly cooled,
which then re-enter
the atmosphere at hypersonic velocities where
they are re-heated
and further modified in their descent to the
surface of the
Earth.
It sounds perfectly reasonable. It
powerfully explains the
great variety of tektite shapes and many
