Obviously, either no one here heard this, or more likely, it simply did not meld with their preconcieved notions, and they simply could not comprehend it - it was outside their conceptual and perceptual space - oh well... Given that ou Mr Eby has been quoting Shoemaker's earlier views to me for some years now, I wonder if he'll follow Shoemaker's example and admit that he was mistaken... No, that's expecting entirely too much of him... he's simply not in Shoemaker's league...

EUGENE SHOEMAKER'S FINAL VIEWS ON THE COMETARY IMPACT HAZARD?
E.P. Grondine epgrondine@hotmail.com

Hello Benny -

While cleaning out my files the other day, I cam across the following messages to the meteorite list from Victor Noto, which describe a video recording of Eugene Shoemaker's final views on the cometary impact hazard. I did not realize their significance at the time, and I have not seen the video myself. I do not know if it is still available today, but I think that some Conference participants may find Noto's synopsis of it to be of interest.

To List:

I just got finished listening to Dr Gene Shoemakers last lecture on a VCR tape that I got from Robert Dick ELPA Production P.O. Box 79 Rideau Ferry, ON Canada KOG 1WO
http://www.physics.carleton.ca/~rdick/

It was not really that easy to hear, the audio was homemade kind of, but the point Shoemaker was making over and over to me is that we are now in the middle of a cometary shower of the type that killed off the dinasaurs 65 million years ago, and he was ninety percent sure that all or most all of the large impactor craters on Earth were the result of comets not
asteroids.

These cometary showers last several million years but the chart Gene showed put us right now on a peak of a flux shower twice that of any other period in the last 70 million years.

Anyone who listened to this tape got anything different? - Victor

Hello Victor,

It's interesting that this ties in with Ramphino's thought about a 30 million year extenuation cycle believed to be triggered (or helped along) by the solar system passing through the galactic lens and perturbing the orbits of cometary bodies in the Oort cloud into the inner solar system. We passed through the lens a few million years ago and could be seeing increased activity as a result. Of course, "cometary shower" should not be thought of as a deluge of
comets, although increased activity always means a increased chance of an impact. On the plus side, comets are *usually* easier to spot than asteroids.

Did Shoemaker give any explanation for "knowning" the cometary activity for the past 70 million years? - Gene Roberts

Hi Gene and List:

I will have to listen to the Shoemaker VCR tape a few more time to remember the details. Shoemaker said that a paper in, I think it was, "Nature" magazine in 1995 got him started, and I think the author was Ken Burns, and he mentioned several other scientists. The paper which I am sure was his main visual aid at the lecture reported to show increases in cosmic dust
particles of a certain size or range of sizes which increased during these past 70 million years and how the cosmic dust directly related to increased impact flux rates. Shoemaker was excited about the paper and contacted the scientist involved and decided to do his own research in Italy which ultimately confirmed the same chart information with geological data of
shocked quartz in strata over the same period.

Shoemaker confirmed that he thought ultimately the impact rate over the last 3.2 billion years was related to the travel of the solar system (Sun and/or Earths) travel around the galaxy. He made special note of the z motion of the Sun in relation to other G type suns and how the our Sun only moves 75 parsecs through the galactic plane and other stars of similar type
the z motion was 300 parsecs(z motion = up and down motion). Gene indicated that this shorter z motion put our solar system in the area of dense star clusters for a longer time and this may strip the Oort cloud of its outer shell of material causing increased cometary activity some period of time following the passage by other stars... - Victor

Well, Benny, that's it. I sure would like a copy of that tape, and my guess is
that there are quite a few others out there who would like to see it too.

Best wishes,
Ed

(8) EUGENE SHOEMAKER'S VIEWS ON THE COMETARY IMPACT HAZARD

Robert Dick <rdick@ccs.carleton.ca>

Hello Mr. Peiser

The videotape you identify is indeed still available. I try to videotape all
presentations I have the good fortune to attend. A copy of the tape was sent to
the Shoemakers after the lecture (as per their request on the copyright release
form). Unfortunately, Eugene never saw it. It was many months before Caroline
was well enough to view the tape.

With assistance from friends, she had the tape transcribed and the result was
Eugene's last published paper. I do not remember the volume and number, however,
it was in the Journal of the Royal Astronomical Society of Canada. The issue was
about 1 or 2 years after Eugene's death. I don't have my archive of Journals
with me. Perhaps Chuck may be able to find the reference.

Robert Dick
Physics, Carleton University
Ottawa, Canada

NOTE: Charles O'Dale <codale0806@rogers.com> writes:

IMPACT CRATERING THROUGH GEOLOGIC TIME
by Eugene M. Shoemaker

Journal of the Royal astronomical Society
December 1998 - Volume 92, Number 6, pages 297-309

Charles O'Dale
Meeting Chair
Ottawa RASC
http://www.ottawa.rasc.ca/astronomy/earth_craters/index.html