PLEASE NOTE:


*

CCNet DIGEST, 7 June 1999
-------------------------

(1) BACK FROM THE TORINO IMPACT WORKSHOP
    Benny J Peiser <b.j.peiser@livjm.ac.uk>

(2) DEBRIEF ON TORINO IMPACT WORKSHOP
    Jonathan TATE <fr77@dial.pipex.com>

(3) LARGEST IMPACT STRUCTURE DISCOVERED IN FRANCE?
    Pierre-Alex Vachon <avachon@src-mtl.com>

(4) ELONGATED ASTEROIDS BELIEVED TO BE WEAKER
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(5) OCEANIC MEGA-IMPACTS AND CRUSTAL EVOLUTION
    Andrew Glikson <geospectral@spirit.com.au>

(6) NEW TUNGUSKA EXPEDITION
    Luigi Foschini <foschini@pinocchio.fisbat.bo.cnr.it>

(7) SYPOSIUM ON PLANETARY IMPACT EVENTS & THEIR CONSEQUENCES ON EARTH
    Ron Baalke <baalke@ssd.jpl.nasa.gov>

(8) AUSTRALASIAN TEKTITE AGE PARADOX
    Bernd Pauli HD <bernd.pauli@lehrer1.rz.uni-karlsruhe.de>

(9) IMPACT EARTH
    Austen Atkinson <ultrazone@easynet.co.uk>


==============
(1) BACK FROM THE TORINO IMPACT WORKSHOP

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

After four days of presentations, deliberations and decisions, the
IMPACT workshop in Turin ended last Friday on a very positive note.
Despite a number of minor disagreements, there is a general
perception that international research on the impact hazard and NEO
searches are gearing up and moving in the same direction. With
additional search programmes planned in a number of countries in the
next couple of years, the sky coverage is soon approaching
saturation. Obviously, achieving such a comprehensive coverage would
be a major breakthrough. Yet it remains questionable whether it would
actually guarantee the Spaceguard Survey's goal of detecting 90% of
all NEOs >1km within the next 10 years. Other problems will also have
to be addressed: the search for fainter objects (< 1 km) requires
access to sufficiently large telescopes; how will we deal in the
event of an undetected (or, indeed, detected/predicted) Tunguska-type
impact? Follow-up searches will remain important for any calculation
of potential impact hazards.

In a politically important statement, directed at national governments
and funding agencies, the participants of the IMPACT workshop strongly
recommend that governments should establish national Spaceguard centres
and to support these centres financially in order to facilitate
international collaboration in the global Spaceguard programme.

One of the more practical results of the IMPACT workshop was the
general agreement on a much improved hazard scale in conjunction with
the question of how to deal with future predictions of possible
impacts by a sizeable near-Earth object. While the exact details will
be finalized by the IAU in the next four weeks or so, there is now a
generally accepted tool on which future cases such as XF11 and AN10
can be handled in a better way. The final results and recommendations
of the workshop will be published in July/August.

And finally - can I just say that it was a pleasure to meet almost
20% of CCNet subscribers at Turin - most of whom I had never met
before. Putting a face to a name and meeting individuals on a
one-to-one basis has certainly helped to improve the communication
and discussion among many participants. I am particularly glad that
some of the mistakes and misunderstandings regarding the recent AN10
debate were sorted out in an amicable manner.

I have attached below Jay Tate's workshop debrief which only
highlights some of the issues discussed at Torino. I am sure
that further reports, impressions and comments will follow. 

Benny J Peiser

===================
(2) DEBRIEF ON TORINO IMPACT WORKSHOP

From Jonathan TATE <fr77@dial.pipex.com>

A "HOT DEBRIEF" ON THE WORKSHOP ON "INTERNATIONAL MONITORING PROGRAMS
FOR ASTEROID AND COMET THREAT" (IMPACT), HELD IN TORINO, ON JUNE 1-4,
1999.
 
The Sponsors of the workshop were the IAU, ASI, NASA, ESA, Spaceguard
Foundation, IACG, The Planetary Society, Alenia Aerospazio - Divisione
Spazio and the Provincia di Torino.
 
This meeting was a follow up to the IAU WGNEO sponsored workshop on the
island of Vulcano (Italy) in September 1995, entitled "Beginning the
Spaceguard Survey". The aim of that workshop was to emphasise the need
for a co-ordinated effort, and to establish the basis for effective
international co-operation on the subject.
 
Participation at the Turin workshop included a high proportion of the
world expertise in NEO studies, and high ranking members of NASA, the
IAU and other sponsoring organisations.
 
The objectives of the workshop were:
 
* To encourage scientists in all nations and their sponsoring
  agencies to increase NEO search and follow-up efforts.
* To improve communications among observers worldwide and to use
  these improved communications to foster co-ordination of search and
  follow-up activities.
* To assess the actual potential and limitations of ground-based
  observing facilities, and to discuss the possible role of space-based
  segments in NEO search.
* To develop procedures for assuring a rapid communication of
  accurate information about Extremely Hazardous Objects which may be
  detected in the future.
* To draft and discuss Recommendations to be distributed to the
  scientific and political bodies able to support and fund NEO
  researches.
 
The structure of meeting was to hold an initial plenary session during
which the conference was briefed on a number of topics, to bring
everyone fully up to date with recent developments. After the briefings
the conference split up into four sub-groups to discuss specific issues,
and to produce recommendations to be passed to the IAU. These
recommendations, once agreed by the sub-groups were then discussed at
another plenary session where they were agreed by the floor, or not.
 
While it is not yet possible to detail the recommendations that will be
passed to the IAU, as they have yet to be "word-smithed" by the
sub-group chairmen and agreed in their final forms, it is possible to
list a few of the significant statements made, discussions had and
recommendations made. So, below are some bullet points, to be followed
by a full report as soon as the results are published.
 
* Actual impacts are likely to be preceded by prior close approaches.
* Comets pose a much smaller risk than asteroids.
* Issues of funding and national interest need to be addressed.
* The issue of whether asteroids are rubble piles or solid bodies is
  still unresolved. This information is very necessary for any
  mitigation strategies. We need 4m-10m class telescopes to do
  compositional studies on NEOs.
* Alan Harris of JPL estimated that about 18% of 1 km and above
  sized NEOs have been discovered, but there are large population
  uncertainties. However, we are still discovering asteroids at too
  slow a rate (8-20 times).
* There are currently a number of space missions to asteroids and
  comets. This is a "Golden Age" for studying comets and asteroids
  according to Don Yeomans.
* NASA is increasing funds for NEO research, and has set up its
  own US JPL program office.
* UK efforts need increased government interest. Recent events
  have shown that there is official acceptance of seriousness of
  problem. In the UK we have a wealth of experience, even in (eg) 4m
  class telescopes. VISTA could be a wonderful tool.
* Japan is pressing ahead with its new NEO detection programme..
* There is an urgent need for some follow up programmes, and more
  funding (staff) for the MPC. Ted Bowell proposed changes to the MPC
  that were highly controversial, raising questions of control and IAU
  international control. No consensus was reached.
* European possibilities were discussed eg DLR, ODAS, including
  the use of ESO facilities.
* The number of inner Earth objects is thought to be similar to
  the number of Atens. Both can be easy to find, provided that you look
  at smaller solar elongations.
* Group 1 discussions emphasised the need for S. Hemisphere
  telescopes (economic and political).
* Group 2 discussions emphasised the need for research into NEO
  physical characteristics.
* In Group 3 the importance of precoveries and plate log searches
  was stressed. There was some emphasis on UKST archive.. This would
  also be an obvious role for the NSC. There was a strong
  recommendation that analysis of PHAs should always be performed by at
  least two independent groups.
* Group 4 developed a protocol, primarily for IAU purposes,
  dealing with the announcement of PHOs. In the plenary session there
  was some confused discussion, and eventually a shorter agreed
  document was approved. This emphasised the need for individual
  nations to discuss the issue; what do public, politicians and
  decision makers require? The need for a National Spaceguard Centre is
  obvious.
* R. Binzel discussed his new hazard scale, but J. Tate has
  already produced something broadly acceptable for UK purposes. This
  scale is designed for use when talking to the general public or the
  media. D. Morrison observed that "people just don't understand
  probability". S. Isobe reckoned that the index was a good lecturing
  tool, but not good for communicating with the mass media.
 
Please be aware that this is a far from complete report, but I hope that
something of the workshop's flavour comes through.

Jay Tate
 
Spaceguard UK

=================
(3) LARGEST IMPACT STRUCTURE DISCOVERED IN FRANCE?

From Pierre-Alex Vachon <avachon@src-mtl.com>

A friend from France just sent me the June issue of the credible and
serious "Sciences et Avenir" entitled: The Biggest Meteorite of the
World.
 
Apparently, geologists who were re-analyzing Landsat 2 pictures of
Rochechouart and Bizeneuille, two adjacent areas of south-western
France, discovered that the two already known 20 km-wide craters were
in fact 200 to 300 km wide!  There shock waves actually touched each
other, as their impats were 140 km apart, 200 million years ago.
 
The Rochechouart impact is said to be the biggest meteorite that has
crashed on Earth!  It is taken for granted that the two impact 
structures came from the same asteroid, and only a few seconds
separated them. Further research has revealed that other 200 million
year old impacts have the same latitude:  Manicouagan (Québec) and
Saint-Martin (Canada). Red Wing (USA) and Obolon (Ukraine) are also
located on the same path that can be traced between Manicouagan and
Rochechouart. Remember the multiple impacts on Jupiter? Same phenomenon
here, they say.
 
This chain of impact is thought to be one of the five most important
catastrophes that have happened on Earth. They estimate the
Rochechouart meteorite measured 15km and the Bizeneuille one perhaps
even bigger. The suggest that the impacts were the equivalent of 40
million Hiroshimas (yes 40 million), affecting thousands of square km
in the Northern hemisphere. They would also explain the presence of the
purest quartz found on Earth. It is used by Nasa and other aerospace
manufacturers.
 
As for the origin of these two meteorites, the article mentions the
theory of the tenth planet, an outsider-kind of a planet, at the limit
of our solar system. It could be responsible for "fishing out" comets
from the Oort Cloud where they are thought to be circulating in great
numbers. Apparently, this theory is controversial.
 
The article ends on a question mark:  will an even bigger meteoritic
impact be found on Earth? They seem to point to Manicouagan in Northern
Québec, where they found a 70 km-wide core. The further study of
satellite images will tell us, it concludes.
 
If anyone is interested, I could scan and put the entire article on the
list. It is in French.  Let me know.
 
A la prochaine!
--
Pierre-Alex Vachon - avachon@src-mtl.com
Réalisateur - Director
Emission Branché - http://radio-canada.ca/branche/

=================
(4) ELONGATED ASTEROIDS BELIEVED TO BE WEAKER

From Andrew Yee <ayee@nova.astro.utoronto.ca>

Public Affairs Office
Lawrence Livermore National Laboratory

Contact: Stephen Wampler
Phone: (925) 423-3107
E-mail: wampler1@llnl.gov

FOR IMMEDIATE RELEASE: June 1, 1999

NR-99-05-03

ELONGATED ASTEROIDS BELIEVED TO BE WEAKER

LIVERMORE, Calif. -- Elongated or stretched asteroids in space are apparently
weaker than spherical asteroids, a scientist at the Department of Energy's
Lawrence Livermore National Laboratory will report today. Mark Hammergren,
a planetary scientist at Livermore's Institute of Geophysics and Planetary
Physics, came to this conclusion after studying nearly 850 asteroid
observations by dozens of astronomers.

Hammergren will present his results during the opening day of the Centennial
meeting of the American Astronomical Society in Chicago, Ill. During his
study of asteroid observations, Hammergren found that very elongated
asteroids are never seen to be rotating faster than once every four hours. In
contrast, more spherical asteroids can rotate as fast as once every 2.3 hours.

Such evidence, Hammergren said, provides strong support for the theory that
most asteroids are not tightly-bonded solid chunks of rock, but rather are
loose aggregates of material, sometimes called "rubble piles.."

"Solid asteroids can rotate as fast as they want and still hold together, but
if rubble piles rotate too fast, they'll fly to pieces," Hammergren said. "It
makes sense that more elongated asteroids, which have weaker gravity on
their ends, would be even more prone to break up."

Based on his research, Hammergren theorizes that "rubble pile" asteroids
in space are governed by the same processes that lend stability to piles of
sand on Earth.

"In effect, loose and weak materials in rubble piles have the ability to
support large surface features on asteroids, just as loose sand and weak
dirt can support huge mountains on Earth," he said.

Hammergren also offered two other findings based on his theory of rubble
pile stability.

One is that changes in a rubble-pile asteroid's shape would probably not
occur gradually, but would instead happen cataclysmically, as a series of
massive landslides.

The other is that if such landslides occur on the surfaces of rapidly-
rotating asteroids, parts of the asteroids' surfaces may be thrown off
into space.

Such break-ups provide a possible explanation for the formation of
asteroid moons, which orbit the original asteroid similar to the way the
moon orbits the Earth.

Lawrence Livermore National Laboratory is managed by the University of
California for the U.S. Department of Energy.


================
(5) OCEANIC MEGA-IMPACTS AND CRUSTAL EVOLUTION

From Andrew Glikson <geospectral@spirit.com.au>

Oceanic mega-impacts and crustal evolution
[Geology, 27:337-341 (1999)]
Andrew Y. Glikson
Research School of Earth Science, Australian National University,
Canberra, A.C.T. 0200

ABSTRACT
Lunar mare crater counts, the terrestrial impact flux, and astronomical
observations of asteroids and comets define a consistent impact rate of
4-6 * 10^-15 km^-2.yr^-1 within the inner solar system since the end of
the Late Heavy Bombardment (LHB) ~3.8 Ga ago. Coupled with the observed
crater size vs cumulative crater size frequency relationship of N ~
Dc^-1.8 (N = cumulative number of craters of diameter > Dc), these
rates imply formation on Earth of more than 450 Dc ³ 100 km-diameter
craters, more than 50 Dc³ 300 km-diameter craters, and more than 20 Dc³
500 km-diameter craters. Geochemical and isotopic constraints require
that more than 80% of the projectiles impacted on time-integrated
oceanic crust since the LHB. The injection of shock energies calculated
at >10^8 megatons TNT-equivalent by a Dp > 10 km-diameter projectile
may result in propagating fractures and rift networks, thermal
perturbations, and ensuing magmatic activity. Examinations of the
geologic record for correlated impact and magmatic fingerprints of such
events remain inconclusive in view of isotopic age uncertainties.
Potential but unproven connections may be represented by the (1)
Cretaceous-Tertiary boundary (ca. 65 Ma) impact(s), onset of the
Carlsberg Ridge spreading, Deccan volcanism, and onset of the mantle
plume of the Emperor-Hawaii chain; (2) Jurassic-Cretaceous boundary
(ca. 145 Ma) impacts, onset of Gondwana breakup, including precursors
of the east African rift structures; (3) Permian-Triassic boundary (ca.
251 Ma) impact(s), Siberian Norilsk traps, and early Triassic rifting;
and (4) the 3.26 Ga basal Fig Tree Group (east Transvaal) Ir-rich and
Ni-rich quench spinel-bearing impact spherules and contemporaneous
igneous-tectonic activity. Tests of the theory require further
identification and isotopic dating of distal ejecta, impact spherule
condensates, and meteoritic geochemical anomalies.

================
(6) NEW TUNGUSKA EXPEDITION

From Luigi Foschini <foschini@pinocchio.fisbat.bo.cnr.it>

Dear Benny,

I would like to inform you that next July a new scientific expedition
will go to the Tunguska region in order to improve our knowledge
about that event.

You can find more informations at the web page:
 
http://www-th.bo.infn.it/tunguska/
 
The page is continuously updated.

Cheers,
 
Luigi

===============
(7) SYPOSIUM ON PLANETARY IMPACT EVENTS & THEIR CONSEQUENCES ON EARTH

From Ron Baalke <baalke@ssd.jpl.nasa.gov>

International Symposium on Planetary Impact Events and their
Consequences to the Earth

- Space and Earth Planetary Circumstances -

Yamaguchi, September 27-30, 1999

Scientific Targets:

This symposium has scientific targets to discuss catastrophic events on
lunar formation, impact craters, meteorites, meteoritic showers, geological
boundaries, space debris, new materials, artificial impacts and life
chemical evolution as analyses of space and terrestrial circumstances.

http://www.sci.yamaguchi-u.ac.jp/geo/PIECE1.html

================
(8) AUSTRALASIAN TEKTITE AGE PARADOX

From Bernd Pauli HD <bernd.pauli@lehrer1.rz.uni-karlsruhe.de>

TAYLOR S.R. (1999) The Australasian tektite age paradox (MAPS 34-3,
1999, From the Editors, page 311):

Students of tektites possess the interesting property of dividing
themselves into two irreconcilable camps. Even the embers of the long
dead lunar vs. terrestrial origin debate are still occasionally
rekindled into flame. Another division of longstanding has concerned the
age of fall of the tektites of the Australasian strewnfield that covers
about ten percent of the surface of the Earth. Early workers, including
such astute observers as Charles Fenner, George Baker, and Edmund Gill,
who picked up pristine tektites on the arid and ancient surface of
Australia, became convinced that this shower of glass had arrived very
recently. Ages around 10 000-20 000 years were usually quoted. As some
early radiometric age determinations of tektites gave spuriously old
ages, these data fuelled the notion that the age of the fall was
disconnected to the time of formation of tektites. It was then a short
intellectual leap to bring them from outside the Earth. More precise
dating eventually yielded ages ca. 770 000 years for the time of
formation of the glass. As the flanges on the famous button-shaped
australites gave effectively the same result, this also marked the
time of entry through the atmosphere of these aerodynamically shaped
forms. Thus the time of formation and fall was close. Then
microtektites were discovered in drill cores from deep-sea sediments,
close to, but not identical with the Brunhes-Matuyama Boundary. This
evidence from two separate disciplines convinced most workers that the
Australasian tektite event had occurred about three quarters of a
million years ago. The stratigraphic evidence was relegated by most
workers to an uncertain status on account of the difficulties of
dating Pleistocene land surfaces in Australia.

A number of workers familiar with the Australian localities continued to
insist on a recent fall (e.g., Lovering et al., 1972) relegating the
awkward deep-sea microtektite data to a separate event. Their position
was reinforced by fieldwork by Izokh (1993) in Vietnam, clearly part of
the same strewnfield, where he claimed a 10 000 year age for the fall.
However work from Vietnam, reported by Fiske et al. (1996), has shown
that "the tektite-bearing horizon represents a paleo-erosional surface"
and "because the tektites are not presently in a chronostratigraphic
horizon, their stratigraphic age is uncertain" (p. 40). Studies in this
area are aided by the exposures in the myriad bomb craters resulting
from the Vietnam war. This information is possibly the sole beneficial
result of that expensive and ultimately futile bombardment.
Robert Fudali (1993) had previously drawn attention to the fact that
most australites showed signs of weathering and transport and that
perfect specimens constituted only a very small fraction of collections.
He noted that at the Port Campbell, Victoria locality, the australites
appeared to be coming from a deeper sandy horizon rather than the
present surface, all this suggesting that the young age was in error.
At this stage, GENE SHOEMAKER, long familiar with the tektite problem,
entered the scene. In conjunction with Ralph Uhlherr and assisted in the
field by his indefatigable wife, CAROLYN, he began mapping the Port
Campbell area. Gene was a superb field geologist whereas Ralph, who had
been collecting tektites in the area for many years, has an intimate
knowledge of the local geology. Their combined work (Shoemaker and
Uhlherr, 1999) has pinned down the precise horizon, the Hanson Plain
Sand, from which the tektites found in younger deposits have been
reworked. The famous stratigraphic paradox has been resolved.
The paper by Gene and Ralph was prepared for press by Carolyn, following
the tragic accident that has deprived us of the great services of Gene.
It was typical of  GENE  that in his final scientific contribution he
settled a major scientific controversy by  m e t i c u l o u s  field
work. This reminds us that his first was to establish, by studies at
Meteor Crater, that the origin of both terrestrial and lunar craters was
due to meteorite impact rather than volcanism.

Stuart Ross Taylor - Associate Editor

Copyright property of the Meteoritical Society, 1999.

=================
(9) IMPACT EARTH

From Austen Atkinson <ultrazone@easynet.co.uk>

Benny/CCNET members,

Reaction to Impact Earth has been overwhelmingly positive, thus far. I
only hope that it helps to spread the word about the impact threat to
the uninitiated. Certainly the TV and radio interviews that I have
given over the last two weeks have resulted in a lot of positive
feedback - even from the British governmental elite!

For those who might be interested in meeting me or coming along to ask
questions/see my talk, there are a number of bookshop events yet to take
place, following the success of the event at Books Etc (Whiteley's,
Bayswater) on May 27th. The dates and locations are as follows:

Tuesday 8th June
7.00 - 9.00 pm Waterstones Contact: Nial Duff Tel: 0141 333 1915
Venue: 153 - 157 Sauchiehall Street Glasgow

Thursday 10th June
6.00 - 8.00 pm Dillons Contact: Peter Oakes Tel: 01483 457545
Venue: 50-54 High Street Guildford, Surrey GU1 3ES

If you would like to contact me, send an email to:
Austen Atkinson <ultrazone@easynet.co.uk>

or visit the Impact Earth website at the following URL:
http://easyweb.easynet.co.uk/~ultrazone/book_signing_promo1.html

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CCCMENU CCC for 1999

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