PLEASE NOTE:


*

Date sent: Wed, 04 Mar 1998 12:19:53 -0500 (EST)
From: Benny J Peiser B.J.PEISER@livjm.ac.uk
Subject: CC DEBATE, 04/03/98
To: cambridge-conference@livjm.ac.uk
Priority: NORMAL

CAMBRIDGE-CONFERENCE DEBATE, 4 February 1998
--------------------------------------------

(1) MOON IMPACTS AND IMPACT RATES
Victor D. Noto vnn2@phoenixat.com

(2) MANY MOON IMPACTS & CRATERS TOO SMALL TO BE VISABLE BY TELESCOPES
Simon Jeffery csj@star.arm.ac.uk

(3) 1-km IMPACT CRATER ON VISABLE FACE OF MOON EVERY 10,000 YEARS
David Morrison dmorrison@mail.arc.nasa.gov

(4) SMALL IMPACTS ON MOON EVERY ~30 YEARS
Alan W. Harris awharris@lithos.jpl.nasa.gov


==========================================
(1) MOON IMPACTS AND IMPACT RATES

From: Victor D. Noto vnn2@phoenixat.com

David

I can not think of a better experiment to test for impact rates than to
put out a ball (the moon) about 1/4 the size of the Earth about 240
thousand miles into a stream of supposed rocks passing by our planet
and look for how many impacts are made on that ball (the moon). It does
not take too big a rock to make a fair size crater. Meteor crate is
7/10 of a mile in diameter and the meteor was only 35 meters on impact.
If we even took pictures of moon periodically, we should note increased
numbers of craters showing up if the impact rate as high as even twelve
a year. Did not the apollo astronauts leave a seimograph on the moon
that could detect impacts on the moon? I think I remember that they
did. So far I have not heard of or seen a picture of even a small new
impact crater on the moon in 25 years. Not one picture - nothing. So
far as I can tell there is no empirical data for impact rates only
conjecture based on statistical data of the supposed number of a given
size rocks in our near space.

Is there any empirical study which proves your figure of 100 fireballs
per year as you say?

Victor

================================
(2) MANY MOON IMPACTS & CRATERS TOO SMALL TO BE VISABLE BY TELESCOPES

From: Simon Jeffery csj@star.arm.ac.uk
To: Victor D. Noto vnn2@phoenixat.com
Subject: Re: meteors hit moon regularly right?

Dear Victor

I am not an expert on this, but asking around I learnt the following.

The earth is hit by about six 1 meter sized objects per year. The
gravitational cross-section of the moon is approximately 1/20th of the
earth's, so the average impact rate on the moon would be about one 1
meter class object every three years. However, craters formed by
objects of this size are too small too see with available telescopes.

The youngest visible crater that we are aware of was formed about 1100
AD.

A boulder swarm hit the moon in 1975. It was detected by seismometers
left behind by the Apollo missions. The experiment was turned off later
that year.

I believe that the third fact provides the evidence you are looking
for, but I cannot provide chapter and verse for the reference.

regards,
Simon Jeffery
--
Dr C Simon Jeffery email: csj@star.arm.ac.uk
WWW: http://star.arm.ac.uk/~csj/
Armagh Observatory, College Hill, tel: +44 1861 522928
Armagh BT61 9DG, Northern Ireland fax: +44 1861 527174

------------------------------------------
(3) 1-km IMPACT CRATER ON VISABLE FACE OF MOON EVERY 10,000 YEARS

From: David Morrison dmorrison@mail.arc.nasa.gov

Victor:

I think that Simon Jeffery has given you a good response. There are
lots of data from the lunar seismic experiments, from decades of
fireball surveys, and from the Defense surveillance satellites that
define quite well the incidence of impacts in the "fireball" range. It
is because of those data that we know the Lou Frank mini-comet theory
is wrong. My only addition is to note that Jeffery's reference to an
observed new lunar crater in 1100 is highly questionable and is not in
fact widely accepted (although it has frequently been mentioned as a
possibility).

Don't take my "100 fireballs" seriously -- the number depends on how
you define a fireball. According to most definitions the number is much
larger than 100 per year. At least a dozen of these are large enough to
be detected from space, so the flux from the upper size end of this
range is well determined. In contrast, we would expect a new 1-km
crater to form on the visible face of the Moon only about once per
10,000 years -- not a practical way to measure the flux.

David Morrison

=============================
(4) SMALL IMPACTS ON MOON EVERY ~30 YEARS

From: Alan W. Harris awharris@lithos.jpl.nasa.gov

Dear Dave (and Victor),

I would add only that one of the five papers which recently appeared in
GRL refuting Lou Frank's mini-comet hypothesis was in fact a
re-examination of the lunar surface in search of new craters. Grier
and McEwen (Geophys. Res. Lett. 24, 3105-3108, 1997) examined 5.2 x
10^4 km^2 of lunar terrain which was imaged at high resolution by both
the Apollo missions in the early 1970's and Clemintine in 1994. If the
Lou Frank hypothesis were correct, they should see about 10,000 new
small craters in that area. They found none. This same survey places an
upper limit on the actual rate of such impacts of around 30 per year.
Keep in mind that this is only an upper limit based on zero detections;
the real value is likely much, much less. They were considering objects
of 5-10m diameter, which should make craters or at least bright
disturbances of the regolith at least 50 m in diameter. These putative
objects are much larger than "fireball" size.

Cheers,
Al



CCCMENU CCC for 1998

The content and opinions expressed on this Web page do not necessarily reflect the views of nor are they endorsed by the University of

The content and opinions expressed on this Web page do not necessarily reflect the views of nor are they endorsed by the University of Georgia or the University System of Georgia.