[meteorite-list] Re: [ I.M.C.A. ] FW: Lunar origin of tektites

From: Norman Lehrman <nlehrman_at_meteoritecentral.com>
Date: Fri Mar 25 15:22:34 2005
Message-ID: <20050325202232.46485.qmail_at_web81004.mail.yahoo.com>

List(s), Bob M., and Norbert C.

Thanks in particular, Bob, for your comments.

It's good to hear an insightful reaction to Chapman's
paper. As you might imagine, it's pretty damned
impressive to anyone lacking the very high level of
knowledge required to give it a critical evaluation.
It apparently passed peer review at the time of
publication, so beyond that, I have to wait for
someone like you to take it a step further.

Make no mistake, I am no champion of the lunar story
and have long accepted it as a neat idea on the
scrap-heap. Hence my surprise when someone I respect
raised the issue again. (And Norbert, you
misunderstood my comments. The lack of a known impact
site is not given as evidence for a lunar origin. It
only intimates that there is something that we don't
yet understand. That leaves us scratching our heads
and reviewing the whole story).

My point in raising the Chapman publication is that,
right or wrong, the lunar story was not promoted by a
lunatic fringe. Perhaps overenthusiastic, perhaps
misguided in view of modern understanding and
information, but none-the-less, serious scientists
trying to examine a hypothesis with the best tools
they could devise.

Insofar as I work with the geology of the earth daily,
and have done so hands-on for over 35 years, I am
constantly impressed with the chaos in the system.
Surely there is also great order, but a lot of
weirdities happen locally. I tend to tune out most
statements about natural systems that use the words
"always" or "never". Hence, I am also not quick to
absolutely rule out ideas.

Suppose we were extra-terrestrials visiting earth. We
have a few hundred kilos of specimens from very local
sites and another 30 or 40 meteorites derived from the
earth. Just how sweeping and conclusive should our
statements about the earth be? Could there possibly
be anything we would not yet know?

For goodness sake, consider our own planet from an
earthling's perspective! I hope no one on this list
supposes we now know all there is to know about earth.
 How many earth specimens have we studied in minute
detail? How many processes have we witnessed? How
much more have we studied in the geological record?

Do we do well to assume we have definitive answers
about all lunar questions?

Bob, I am not challenging your trajectory studies,
etc. Those are exactly the kinds of analyses needed.
This is directed more to those who assume we know all
the answers.

I keep getting the feeling that I'm coming down as a
champion for the lunar story. Not so. But I do
understand that we haven't got it all figured out, so
I'm still listening (to all who don't use "always" or
"never" toooo much----)

Regards,
Norm
http://tektitesource.com






--- "Matson, Robert" <matsonr_at_saic.com> wrote:

>
> Resending this message, which as usual did not post
> to the IMCA
> message group. I'm CCing Meteorite Central in case
> it fails to
> show up at IMCA a second time. --Rob
>
> -----Original Message-----
> From: Matson, Robert
> Sent: Thursday, March 24, 2005 11:47 PM
> To: 'meteoritecollectorsassociation_at_yahoogroups.com
> '
> Subject: Lunar origin of tektites
>
>
> Hi Doug and List,
>
> Some of you (most of you?) are probably already
> aware of my position
> on the lunar origin of tektites, but for those who
> don't I'll throw
> in my two cents from the dynamics standpoint. Short
> answer: no dice.
>
> Years ago I didn't have an opinion or a vested
> interest one way or
> the other -- I was honestly curious if the lunar
> origin could be
> dynamically supported. So I modeled it and ran
> millions of Monte
> Carlo simulations to see where either volcanic or
> lunar impact
> ejecta material would end up. The answer is: if an
> intercept is
> possible, it rains down on more than a hemisphere of
> the earth (as
> well as significant portions either back on the Moon
> or in solar
> orbit). There is no natural way to favor a
> geographic region on
> the earth when the Keplerian trajectory origin is on
> the Moon. The
> angular tolerances are just too tight.
>
> Lunar volcanism is an even more restrictive case
> since it requires
> the initial velocity vector to not only deviate
> significantly from
> the local lunar zenith direction, but in exactly the
> correct direction
> for an earth intercept. Anything other than a
> direct intercept
> path on a pencil-thin beam results in tektites
> scattered over more
> than a hemisphere.
>
> > I am eating up Norm's comment that some bona fide
> Indochinite
> > researcher out there (an endangered species), is
> mulling over the
> > possibility of Lunar origin for Indochinites as
> this is EXACTLY
> > what I was implying in my last post about all
> glass not being
> > equal and a certain tektite not-so-hypothetically
> being proven
> > to be of Lunar origin.
>
> Not one researcher has offered a scenario by which a
> lunar impact
> results in tektites scattered on the earth in not
> only a limited
> geographic area, but with a non-elliptical pattern.
> The earth is
> a tiny enough target from the Moon's distance; to
> generate the
> limited (and non-elliptical) distribution of tektite
> finds requires
> a reasonable dynamic mechanism. None has been
> offered that can
> be mathematically reproduced.
>
> Norm wrote:
>
> > ... Dean Chapman's 1971 article in the Journal
> of Geophysical
> > Research ... looked at australasian distribution
> patterns and
> > demonstrated that they are consistent with
> theoretical
> > distributions of ejecta from a particular ray of
> crater Tycho
> > is more than a statement of opinion.
>
> I studied the special case of Tycho precisely
> because of Chapman's
> paper. Ignoring for the moment that the Tycho
> crater is believed
> to be about 100 million years old, I found the
> results irreproduce-
> able. Would love to see Chapman's source code to
> see what assumptions
> he made, but based on the lunar latitude and
> longitude of Tycho,
> and the azimuth angle of the Rosse ray, I do not
> come up with a
> direct intercept solution for the earth, no matter
> what one chooses
> for the local lunar elevation angle and initial
> velocity of the
> tektite precursor fragments.
>
> --Rob
>
>
>
>
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Received on Fri 25 Mar 2005 03:22:32 PM PST