[meteorite-list] Tektite/moon semantics

From: Matson, Robert <ROBERT.D.MATSON_at_meteoritecentral.com>
Date: Thu Apr 22 10:04:46 2004
Message-ID: <AF564D2B9D91D411B9FE00508BF1C86901B4E117_at_US-Torrance.mail.saic.com>

Hi Steve,

I think you misunderstood Alan's question/remark (and taken
out of context, it was really easy to do so). When he asked,

> I do not think you mean to say that a tektite fell
> from the Moon to the Earth, Do you?

He was referencing your sentence (brackets mine):

> There is no mechanism by which such [tektites] could possibly
> survive in that form [stretch] after having entered the
> earth's atmosphere at the requisite velocity of 7+ miles
> per/sec after having fallen the distance from the moon
> to earth.

I think everyone here knows that you (and pretty much everyone
else) do not believe that tektites came from the moon. I think
Alan was focusing on the ~wording~ of your phrase, "...after
having fallen the distance from the moon to earth." I know
what you meant, but to a newbie it could be confusing. The
important technical point you were making is that the moon is
sufficiently far outside earth's gravity well that any material
coming from the moon to earth (by whatever mechanism) must
have a MINIMUM velocity equal to earth's escape velocity of
11.18 km/sec (~ 7 mi/s). Such a high velocity certainly places
limits on the forms that silica can exhibit after passage
through a dense atmosphere.

As a side note, last year I performed many CPU-hours of trajectory
analysis/orbital mechanics in a Monte Carlo simulation of
transfer of lunar material to the earth via lunar volcanism --
a simulation and modeling problem spurred by my many exchanges
with Darryl Futrell (who, sadly, is no longer with us).

It was a lot of fun working on this problem, seeing the results
of the computer simulations, and trying to play devil's advocate to
come up with *some* way of creating Darryl's lunar tektites. Alas,
I ended up disproving the lunar volcanic origin (initially, and
rather trivially, for Tycho, but later extended to any lunar
volcano) purely from a celestial mechanics standpoint.

Ignoring tektite morphology for the moment, it is a slightly harder
task to rule out the possibility that a lunar impact event can
create the comparatively focused tektite strewn fields that are
found. This was Dean Chapman's belief, which Darryl replaced
with volcanism. Orbital mechanics was not Darryl's area of
expertise, and while he may have thought it was a minor modification
to replace Chapman's Tycho impact (as the tektite-producing event)
with a Tycho volcanic outburst, the modification was actually
a fatally flawed one because it severely restricted the direction
and magnitude of candidate tektite velocity vectors.

Anyway, if it weren't for Darryl, I never would have learned of
the tektite origin controversy, and thus never had the opportunity
to contribute something to the field. I am saddened that Darryl
passed away before I was able to share my modeling results with
him. If I know Darryl, he would have found a clever loop-hole
in the theory that would have sent me back to the chalkboard
to add new parameters to my simulation. His absence is keenly
felt...

Best,
Rob
Received on Mon 06 May 2002 03:08:00 PM PDT