PLEASE NOTE:


*

CCNet DEBATE: NO END IN SIGHT FOR 1997 XF11 CONTROVERSY?
--------------------------------------------------------

(1) NO END IN SIGHT FOR 1997 XF11 CONTROVERSY?
    Benny J Peiser <b.j.peiser@livjm.ac.uk>

(2) CLARK AND BRIAN
    David Levy <dhlevy@LPL.Arizona.EDU>

(3) THERE WAS NO IMPACT RISK IN 2028
    Andrea Milani Comparetti <milani@copernico.dm.unipi.it>

(4) THERE WAS NO IMPACT RISK IN 2028
    Ted Bowell <elgb@lowell.Lowell.Edu>

(5) CONFLICTING IMPACT PROBABILITIES & WHY THE PUBLIC HAS A RIGHT TO
    KNOW
    Jens Kieffer-Olsen <dstdba@post4.tele.dk>

==================
(1) NO END IN SIGHT FOR 1997 XF11 CONTROVERSY?

From Benny J Peiser <b.j.peiser@livjm.ac.uk>

Clark Chapman's recent article in The Planetary Report (which was
widely circulated on the internet by David Morrison) has re-opened
the debate about asteroid 1997 XF11 and its handling in the public. As
the moderator of the CCNet, I had the option to i) ignore Chapman's
accusation against the MPC and his controversial recommendations to
NASA, ii) forward Morrison's e-mail copy of the article without any
comment, or iii) add a correction of the main inaccuracies of the
article. I decided to do the latter and posted Clark's article together
with an open letter to the Planetary Society.

David Levy has criticised me for that decision, and I certainly must
take some blame for allowing this debate to continue on the CCNet.
Others would like to see an end to any future debate on this or
related issues on the internet (forgetting, however, that NASA was
the first to set up and maintain an NEO e-mail network, and that this
network actually triggered the recent debate). Some of these critics
seem to suggest that the 1997 XF11 controversy is mainly due to its
electronic venue. While I would agree that the internet revolution has
brought about new and unfamiliar problems for scientific debate and
conduct (particularly with regards to the traditional method of 'peer
review' of submitted information to the print media), it should be
recalled that the multitude of accusations against the MPC have been
circulated almost exclusively on the internet. People who live in
glass houses shouldn't throw with stones.

It is also difficult to understand why these critics still pack down
on the alleged impact risk for 2028. As most list members will
be only too aware, this issue was settled conjointly long ago. The
actual disagreement which remains, as readers of my open letter
and Brian Marsden's recent contribution on the CCNet will have noticed,
is that about the small possibility of an impact during the decades
AFTER 2028 which Marsden and others astronomers maintain was a real
concern BEFORE the discovery of the 1990 images ruled out such a risk
for the next 1000 years or so.

Be that as it may, I should make one thing unequivocally clear: I
am in no position - and never have been - to judge who, at the end
of the day, will be proven right or wrong in this debate. Yet I
firmly believe that only a balanced, impartial and scientifically sound
assessment of the conflicting data, calculations and arguments will
bring about a satisfactory solution which is acceptable to all
reasonable researchers and observers. I very much hope that the
displeasing controversy will result in some constructive conclusion
which will bring about a more sophisticated and more reliable method of
assessing the NEO risk in the future. If that could be achived, and I am
sure that it can, the controversy will have served its main purpose
nevertheless.

Benny J Peiser

======================
(2) CLARK AND BRIAN

From David Levy <dhlevy@LPL.Arizona.EDU>

Dear Benny,

I was dismayed to see your end-of-the-year letter regarding 1997 XF11.
I had hoped that the subject was in for some well-deserved down time for
a while. I admire both Clark and Brian, so the fact that the arguments
go on and on is very unpleasant.

I suggest that this issue needs to be put to rest for a while.
Continuing this debate is damaging not just to the people involved but
to the field. 

Sincerely
David H. Levy

=====================
(3) THERE WAS NO IMPACT RISK IN 2028

From Andrea Milani Comparetti <milani@copernico.dm.unipi.it>

I would recommend to read my preprint, available from my preprint home
page

THE ASTEROID IDENTIFICATION PROBLEM III: TARGET PLANE CONFIDENCE
BOUNDARIES, with G.B. Valsecchi, submitted, June 26, 1998 (HTML
version with figures)(postscript gzipped, 155K)

http://copernico.dm.unipi.it/~milani/preprints/preprint.html

which is, after all, the first paper submitted to a major journal about
the 1997 XF11 affair. It contains a precise computation (not a
statement, it appears somebody does not get the difference!) on the
close approaches compatible with the 1997/98 observations.

If you allow me some self-quotation, from this same paper:

"All this is now history, and we shall not comment any further on these
events and on the following discussion, apart from stating that the
appropriate context for a scientific discussion is either a scientific
meeting or a paper in a refereed journal, such as this one; and that,
since the appropriate timescale for scientific research can not be a
few hours, it is not possible to express a real time scientific
judgement on a tricky issue of celestial mechanics, unless the
algorithms have been studied (and published, submitting them to peers
review) in advance, and a well tested software is available. "

"Thus Figure 5 allows to conclude: (1) that the impact risk by 1997 XF can
be found to be essentially zero, even using the 1997-98 observations
only; (2) that the close approach of October 2028 is not constrained,
by the 1997-98 observations, to be at a distance closer than the Moon;
(3) that the linear approximation, successful as it is in this case,
can not be relied upon in every case. All three conclusions have been
also obtained by the Monte Carlo method [Muinonen and Bowell 1993] "

"5.An impact by asteroid 1997 XF  was not compatible with the
observations from the discovery to March 4, 1998, unless it could be
admitted that the RMS observation error was about 4 arc seconds."

Yours Andrea Milani

Dipartimento di Matematica
Via Buonarroti 2
56127 PISA ITALY

tel. +39-50-844254 fax +39-50-844224
E-mail: milani@dm.unipi.it
WWW: http://virmap.unipi.it/~milani/homemilani.html

=====================
(4) THERE WAS NO IMPACT RISK IN 2028

From Ted Bowell <elgb@lowell.Lowell.Edu>

Dear Benny:

The specific issue of whether it was possible to rule out a collision
of 1997 XF11 with Earth in 2028, based on data available on and before
11 March 1998 has, I believe, been unequivocally settled. Please refer
to the abstracts written by Paul Chodas and Don Yeomans (Bull. Amer.
Astron. Soc. 30, 1029, 1998) and by Karri Muinonen (Bull. Amer. Astron.
Soc. 30, 1030, 1998), where you will find two brief expositions on the
matter. Muinonen calculates that observations covering just the interval
6 through 21 December 1997 suffice to reduce the upper bound of the 2028
impact probability to 10^{-42}. Adding subsequent observations makes
the impact probability even smaller. Of course, it remains for the
aforementioned work to appear in the refereed literature, but one can be
confident that it will.

Benny, why do you persist, in the face of evidence like the above, in
arguing that Brian Marsden is correct in asserting that the 1990
observations were necessary to rule out a 2028 collision? If you want
to continue this debate in any rational way, will you please produce
some convincing evidence that supports Brian's viewpoint.

Regards...Ted Bowell

===================
(5) CONFLICTING IMPACT PROBABILITIES & WHY THE PUBLIC HAS A RIGHT TO
    KNOW

From Jens Kieffer-Olsen <dstdba@post4.tele.dk>

Paolo Farinella <paolof@keplero.dm.unipi.it> wrote:

> Actually I belong to a third `group' (the vast majority of the experts, I
> think) who claimed to different things: (1) that an impact in 2028
> could be safely ruled out from the first three months of observation;
> (2)  that as a consequence the short-term (~1 century) hazard posed by
> this object is much lower than the collective hazard level posed by the
> undiscovered NEAs of similar size (the so-called `background level'). I
> think that, after many bitter discussions, Brian Marsden now agrees
> with (1); and I have never seen a calculation by him or anybody else
> showing that (2) is false. Nor I think that there are other issues
> worth being presented to the public in this context.

As a layman I cannot argue with (1) but it seems improbable to me that
the observation of an orbit-perturbing encounter with XF11 in the year
2028 should not increase the overall i.p. for subsequent years, such as
has been repeatedly claimed. Ignorance of which objects contribute how
much to the collective hazard level cannot in my view be used as a
means to dismiss the relevance of an observed hazard however small,
since the estimate of the collective hazard level of unknown objects
suffers from the fundamental limitation of being constant over time. 
The true i.p. as computed in the future from mapped orbits of all PHA's
will fluctuate over time.

I also cannot concur with the conclusion that the XF11 scare should
not have been shared with the public, since awareness of the
potential danger from outer space and the associated uncertainties is
necessary in order to build up an understanding that the ability to
issue firm forecasts requires a certain investment over the next many
decades. And as we are all aware, that's peanuts compared to the cost
of actually obviating an impact!          


*

CCNet DIGEST, 6 January 1999
----------------------------

(1) METEORS BY MOONLIGHT
    NASA Science News <expressnews@sslab.msfc.nasa.gov>

(2) DAVID LEVY'S LATEST ON COMET SHOEMAKER-LEVY 9
    David Levy <dhlevy@LPL.Arizona.EDU>

(3) ASTEROID 20-MASSALIA
    J. Bange, CNRS

(4) ASTEROIDS FROM THE COMETARY FLUX
    V.V. Emelyanenco, SO URAL STATE UNIVERSITY

(5) YET ANOTHER FLOOD THEORY
    The New York Times, 5 January 1999

(6) STAR TREK'S SCIENCE EDUCATION VALUE
    Larry Klaes <lklaes@BBN.COM>

================
(1) METEORS BY MOONLIGHT

From NASA Science News <expressnews@sslab.msfc.nasa..gov>
http://science.nasa.gov/newhome/headlines/ast05jan99_1.htm

Jan. 5, 1999 Meteors by Moonlight

Meteor watching in 1999 began with a whimper, but it could end       
with a bang

Jan. 5, 1999: The first major meteor shower of 1999 has come and gone,
largely hidden from view by the light of last week's full moon. Early
reports from Europe and eastern North America indicate that 15 to 30
meteors per hour were visible in clear-sky locations.

Although the number of Quadrantid meteors was relatively few, some were
spectacular. C. J. Christensen of Weber State University in Utah
observed only 13 meteors per hour on Jan. 4, but he reported "I was
impressed that many [of the meteors I saw] stretched a considerable
distance across the sky. The best example ... appeared to dump off red
sparks as it started to dissipate directly overhead. The light
pollution by 2:30 a.m. was too great and convinced me to quit."

Peter Detterline of the Boyertown Planetarium in Douglassville, PA saw
25 meteors in 90 minutes on Jan. 4, including two at magnitude -1 and
nine near magnitude 0. He commented: [I saw] "four 4th magnitude
meteors under moonlight conditions! Imagine how many could have been
seen on a good dark night." Indeed, next year's Quadrantids probably
will put on a more impressive show when the moon is a waning cresent
during the shower's peak on Jan. 4, 2000.

For more information about the Quadrantid meteor shower visit
www.Quadrantids.com

The passing of the Quadrantids marks the end of the meteor watching
season for most amateur astronomers. The next major shower won't arrive
until late July when Earth passes through the debris stream of comet
Swift-Tuttle, resulting in the Perseid meteor shower. It's a long wait,
but it may be worth it. The 1999 Perseids will signal the beginning of
unusually good series of meteor observing opportunities -- possibly the
best in decades.

The action is expected to begin on August 12, 1999 when the Perseid
shower reaches maximum only two days after a new moon. At its peak in
1998 the Perseid shower displayed as many as 80 meteors per hour
despite the bright light of a moon that was full only 4 days earlier.
Thanks to darker skies the 1999 shower should be even better.

The Giacobinids, the next major shower after the Perseids, will also
benefit from the dark skies of a new moon when it peaks on October 8-9,
1999. Last year's Giacobinids produced an outburst of 500+ meteors per
hour over Japan thanks to the recent passage by Earth of its parent
comet Giacobini-Zinner. The comet will be farther away from Earth this
year, but still in the neighborhood, so the Giacobinids are likely to
put on a good show once again.

Of course the most exciting meteor shower to watch in 1999 will be the
Leonids. On Nov 17, 1999 there is a possibility of an historic meteor
storm consisting of 500 to 10,000 meteors per hour. The highly-touted
1998 Leonid shower put on a display of 400 meteors per hour in some
locations, and sky-watchers around the world were treated to a
rare display of fireballs and long-lasting, colorful meteor trails.
Ranier Arlt of the International Meteor Organization has analyzed data
from 217 experienced observers and noted some similarities between the
1998 Leonid shower and the 1965 shower that preceded the Great Storm of
1966. Does the 1998 shower presage a meteor storm in 1999? That remains
to be seen. Even if the 1999 Leonid shower is no better than the
1998 shower, it should be one of the best sky shows in many years.

Finally, 1999 will close with the Geminid meteors in December. The
Geminid shower has steadily grown in strength for many years and now it
is the most intense of the major annual showers. Like the 1999 Perseids
and Giacobinids, the 1999 Geminids will take place under the dark skies
of a nearly new moon. Over 100 meteors per hour should be visible on
Dec. 13, 1999 when the shower peaks.

Join NASA as a Partner in Discovery

Many of the pictures and observations reported in this article were
contributed by members of the NASA Star Trails Society. The Star Trails
Society is part of the NASA/Marshall Space Science Lab's "Partners in
Discovery" initiative to involve our readers in scientific and
educational research. Several times each month we announce
opportunities for amateur scientists to contribute to activities in
astronomy, astrobiology, and other natural sciences. For more
information or to become a member please visit www.StarTrails.com.

=============================
(2) DAVID LEVY'S LATEST ON COMET SHOEMAKER-LEVY 9

From David Levy <dhlevy@LPL.Arizona.EDU>

Benny,

May I call to your readers attention the following paper:

Thanks

David

---------------
The Collision of Comet Shoemaker-Levy 9 with Jupiter
D. H. Levy
Space Science Reviews 85: 523-545, 1998.

Abstract:  The discovery of Comet Shoemaker-Levy 9 in March 1993
opened an extraordinary few years in the study of the history of
impacts in the solar system.  This review paper offers a background
that attempts to set the events of 1993 and 1994 into a historical
context, and describes events leading to the discovery and the
mounting of a unique and unprecedented international effort to
observe the comet's collision with Jupiter.  A selection of the
results is presented to explore how the fate of Comet Shoemaker-Levy
9 has affected scientific and popular understanding of impacts in the
solar system.

========================
(3) ASTEROID 20-MASSALIA

J. Bange: An estimation of the mass of asteroid 20-Massalia derived
from the Hipparcos minor planets data. ASTRONOMY AND ASTROPHYSICS,
1998, Vol.340, No.1, pp.L1-L4

CNRS, URA 707, BUR LONGITUDES, 77 AVE DENFERT ROCHEREAU, F-75014
PARIS, FRANCE

The ESA astrometry satellite Hipparcos has observed a set of 48 minor
planets between 1989 and 1993. A close encounter between 20-Massalia
and 44-Nysa, both planets observed by Kipparcos, enabled us to obtain a
value for the mass of 20-Massalia. Due to another close approach with
the large asteroid 4-Vesta, the value we obtained (2.42 +/- 0.41
10(-12) M.) is closely dependent on the value assigned to the mass of
Vesta. Copyright 1999, Institute for Scientific Information Inc.

===================
(4) ASTEROIDS FROM THE COMETARY FLUX

V.V. Emelyanenco: Asteroids from the cometary flux (in Russian).
IZVESTIYA AKADEMII NAUK SERIYA FIZICHESKAYA, 1998, Vol.62, No.9,
pp.1898-1901

SO URAL STATE UNIVERSITY, CHELYABINSK, RUSSIA

==================
(5) YET ANOTHER FLOOD THEORY

From The New York Times, 5 January 1999
http://www.nytimes.com/library/national/science/010599sci-black-sea-flood.html

Plumbing Black Sea for Proof of the Deluge

By JOHN NOBLE WILFORD

Two Columbia University marine geologists, inviting incredulity, came
forward in 1996 with astonishing evidence suggesting that a
catastrophic flood of the Black Sea 7,600 years ago could have played a
pivotal role in the spread of early farming into Europe and much of
Asia. The deluge also may have cast such a long shadow over succeeding
cultures that it inspired the flood account in the Babylonian epic of
Gilgamesh and, in turn, the story of Noah in the Book of Genesis.

Now the geologists, Dr. William B. F. Ryan and Dr. Walter C. Pitman III
of Columbia's Lamont-Doherty Earth Observatory in Palisades, N. Y.,
say they have even more archeological, geological and climate data to
support their provocative thesis. They argue their case in "Noah's Flood:
The New Scientific Discoveries About the Event That Changed History,"
a book being published next week by Simon & Schuster.

While the authors have yet to win over skeptics of the Black Sea
flood's possibly sweeping influence on history, other scientists have
weighed in with new findings that seem to confirm the fact of the flood
itself. In about 5600 B.C., with rising global sea levels, salt water
from the Mediterranean and Aegean seas apparently burst into the Black
Sea, then a landlocked freshwater lake. The Black Sea rose with
terrifying swiftness, inundating more than 60,000 square miles of
coastal plains and giving the body of water its current size and
configuration.

The thesis, however it is ultimately judged, has already inspired a wave of
archeological and other scientific research in the previously neglected
Black Sea region.

"It has captured the archeological community's attention and enthusiasm,"
Ryan said in a recent interview. "The atmosphere has changed in just two
years. People from many countries are keen to take part in exploring the
idea in many ways."

Working on Turkey's Black Sea coast at Sinop, Dr. Fredrik T. Hiebert, a
University of Pennsylvania archeologist, has detected possible ruins of
a Stone Age village that was submerged in the flood. He is planning an
expedition this summer to expand the search for preflood settlements.
One objective is to determine if the people were farmers and so, as
refugees from the deluge, might have spread the practice of agriculture
into Europe for the first time.

Dr. Robert D. Ballard, the oceanographer who used modern underwater
technologies to find and explore the Titanic wreck, is preparing an
ambitious survey of submerged Black Sea archeological sites this
summer. Ballard, formerly with the Woods Hole Oceanographic Institution
on Cape Cod, is president of the Institute for Exploration in
Mystic, Conn.

Until Ryan and Pitman advanced their hypothesis, archeologists had little
reason to believe the preflood Black Sea shore was particularly
hospitable.

In the last two years, moreover, new cores from the Greenland ice cap
have revealed that the world underwent a cold, arid period, beginning in
6200 B.C. and ending about two centuries before the flood.
Archeological digs in the Middle East appear to show many Neolithic
settlements' being abandoned during this drought.

"We speculate that this cold and arid period may have driven people to 
the Black Sea as an oasis," Pitman said. "They would have brought
farming with them to this water hole, so to speak, and also exchanged
ideas and languages."

The timing of the flood, Pitman said, happened to coincide with
archeological evidence of newcomers in the Balkans and in northeastern
Europe and with some of the earlier signs of agriculture in these regions.
Some pottery at these sites is similar to that found near the Sea of
Marmara in Turkey from around the time of the flood.

Making connections between people displaced by the flood and the rise
of agriculture in Europe -- even in Egypt and Central Asia -- is the most
controversial aspect of the Ryan-Pitman thesis. In a review of the book in
the current issue of Archaeology magazine, Mark Rose, the managing
editor, said the farming connection "is predicated on a huge archeological
assumption" that there was a drought and it did force Middle Eastern
farmers to find refuge on the preflood Black Sea coast. He also noted
that some farming had already begun to appear in parts of Europe 500
years before the putative flood.

Rose concluded: "If Ryan and Pitman are right about the inundation of
the Black Sea, they have made a real advance in our understanding of
the region's past. But making it Noah's flood and claiming it was the
'event that changed history' was a mistake."

In other recent research, Dr. Gilles Lericolais, a French
oceanographer, led an expedition last spring that conducted more
seismic and echo-sounding probes of the submerged shelf off the Black
Sea coast. He discovered deep underwater canyons where the Danube and
Dnieper rivers had once cut deep to reach the declining waters of the
preflood Black Sea.

Turkish geologists recently reported evidence that, contrary to most
assumptions, the Bosporus Strait was cut at the time of the flood and
not before. At the end of the last ice age, more than 12,000 years ago,
the outlet connecting the freshwater Black Sea to the Mediterranean was
probably a channel through the Sakarya River to the Gulf of Izmit, an
eastern arm of the Sea of Marmara. But this passageway had closed well
before the flood, leaving no outlet for Black Sea's steadily evaporating
and diminishing waters.

"We have no way of knowing what caused the change," Ryan said. The
Sakarya outlet "is on the Anatolian fault, so a slip of the fault may have
choked it up."

In any event, where the Bosporus flows today by Istanbul, separating
Europe and Asia, there was a low valley just before the flood. Ryan and
Pitman propose in their book that a natural dam across the valley kept
the ocean waters, rising since the melting of ice-age glaciers, from
entering the Black Sea basin. This, they said, would explain why the
world ocean did not make contact sooner with the lowered Black Sea and
why, when it did break through, the event was so catastrophic and left
such a deep scar as the Bosporus Strait.

Copyright 1999, The New York Times

=========================
(6) STAR TREK'S SCIENCE EDUCATION VALUE

From Larry Klaes <lklaes@BBN.COM>

This article in the January, 1999 issue of Scientific American
says that Star Trek, while not necessarily being the best place
for learning space science, can be an effective tool for interesting
people into learning more about real science.

http://www.sciam.com/1999/0199issue/0199techbus4.html

Larry


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