PLEASE NOTE:


*

CCNet DIGEST, 15 October 1998
-----------------------------

(1) CHAOTIC ORBITS, NON-GRAVITATIONAL FORCES & AND THE LIMITATIONS OF
    IMPACT COMPUTATION
    Duncan Steel <dis@a011.aone.net.au>

(2) PREDICTIONS, GOOD AND BAD
    THE NEW YORK TIMES, Science Times, page D3, Tuesday, Oct. 13

(3) EUROPEAN GEOPHYSICAL SOCIETY MEETING 1999
    Detlef Koschny <dkoschny@estec.esa.nl>

(4) STILL NO LIMITS TO SCIENCE
    THE TIMES, 15 October 1998
http://www.sunday-times.co.uk:80/news/pages/Times/frontpage.html?1617548

(5) THE PROBLEM OF CONFIRMING THE IMPACT ORIGIN OF SMALL CRATERS
    C. Koeberl et al., UNIVERSITY OF VIENNA

(6) SCALING ANALYSIS OF METEORITE SHOWER MASS DISTRIBUTION
    L. Oddershede et al., TECHNICAL UNIVERSITY OF DENMARK

(7) MICROMETEORITES FROM ANTARCTICA
    C. Engrand & M. Maurette, UCLA

(8) SHOCK-INDUCED EFFECTS OF METEORITE IMPACT CRATERS ON EARTH
    I. Martinez*) & P. Agrinier, IPGP, PARIS

(9) JUPITER'S GREAT INEQUALITY & ASTEROID ORBIT EVOLUTION
    S. Ferraz Mello et al., UNIVERSITY OF SAO PAULO

(10) LIFE FLOURISHED WHEN EARTH WAS WARMER
     Andrew Yee <ayee@nova.astro.utoronto.ca>


===========================
(1) CHAOTIC ORBITS, NON-GRAVITATIONAL FORCES & AND THE LIMITATIONS OF
    IMPACT COMPUTATION

From Duncan Steel <dis@a011.aone.net.au>

Dear Benny,

I found the item:

>G. Sitarski: Motion of the minor planet 4179 Toutatis: Can we predict
>its collision with the Earth? ACTA ASTRONOMICA, 1998, Vol.48, No.3,
>pp..547-561

to be extremely interesting. Lest anyone start bickering about
personalities and whether the people involved know what they are
doing, let me suggest that they immediately remove to a library,
look out Astronomy & Astrophysics Abstracts, and discover for
themselves what epic work Sitarski has done over the years in the
area of dynamics of asteroids and comets, in particular considering
orbital solutions accommodating non-gravitational forces.

Now let me say why I find this paper very significant, given events
of the past seven months.  Sitarski, having available astrometry of
(4179) Toutatis stretching over an arc of 63 years, identifies a
clear but small non-gravitational force.  One presumes that he has
accommodated relativistic effects so that this is not a computational
artifact. The asteroid is therefore, it seems, outgassing: perhaps
an almost extinct comet (or maybe it will spring back into life and
follow an even more chaotic path)?  A ramification Sitarski identifies
is the impossibility of predicting the path of this object over the
next few centuries.

The punchline is so clear that I hardly need to state it. All solutions
for the anticipated orbital evolution of 1997 XF11 are based upon a
presumption that only gravitational influences apply. The observed
arc is (I imagine) too short to allow the identification of
non-gravitional forces of the order identified by Sitarski in the case
of Toutatis. So how sure are we now about the path that 1997 XF11 will
take?

Duncan Steel

==============
(2) PREDICTIONS, GOOD AND BAD

From THE NEW YORK TIMES, Science Times, page D3, Tuesday, Oct. 13

To the Editor:

William K. Stevens makes valid points about scientific predictions
("When Scientific Predictions Are So Good They're Bad", Sept. 29), but
his reference to the stir last March about the possibility of an
asteroid strike in 30 years beautifully illustrates that much of the
problem lies in how scientific information is presented.  My prediction
was merely that the asteroid in question would come close, possibly
uncomfortably close. The statement that there was a "one-tenth of 1
percent" chance of a hit came from another scientist who misinterpreted
what I had said. 

Malcolm Browne's March 12 front-page story ("Asteroid Is Expected to
Make a Pass Close to Earth in 2028") correctly said that there was "no 
immediate cause for alarm", that there was some uncertainty in the
computation of the object's distance and that further observational
data were being sought to narrow down the uncertainty. 

Such data became available later that day, something that would
obviously not have happened in the absence of some kind of
announcement. That resulting refined distance of 600,000 miles for
2028, while safely more than twice the distance of the moon, is still
the closest for any asteroid of which we have advance knowledge until
2086. 

My prediction was not "erroneous."  It was an appropriate conclusion 
from the information available at the time, and it led to the discovery
of the data from 1990 that showed the asteroid to be "safe."  That
outcome was not only encouraging, but also illustrative of how the
scientific process works.

DR. BRIAN G. MARSDEN
Cambridge, Mass.

The writer is the associate director for planetary sciences at the
Harvard-Smithsonian Center for Astrophysics.

=====================
(3) EUROPEAN GEOPHYSICAL SOCIETY MEETING 1999

From Detlef Koschny <dkoschny@estec.esa.nl>

The next meeting of the EGS, the European Geophysical Society, will
take place in The Hague in the Netherlands from 19-23 April 1999.
Session PS8 will be on "Meteors and meteor swarms", convener is Klaus
Scherer at the Max-Planck-Institut for Aeronomy in Lindau, Germany,
Co-Convenor is Peter Jenniskens, NASA. The text in the EGS newsletter
says:

"The new developments in observations and aerodynamics of meteors
should be presented. Special empahsis should be put onto the latest
observations of the Leonid shower during Novemnber 1998 which is
expected to have a huge meteor rate. First results from the
international Leonid observation campaign shall be available."

Also of interest to you might be PS7, Small bodies and dust, Convener
G. Schwehm, ESA.

Check the EGS web page for more info,

http://www.mpae.gwdg.de/EGS/egsga/denhaag99/denhaag99.htm

Detlef/Laffy.

===========================
(4) STILL NO LIMITS TO SCIENCE

From THE TIMES, 15 October 1998
http://www.sunday-times.co.uk:80/news/pages/Times/frontpage.html?1617548

Arthur C. Clarke finds there are still many reasons to boldly go where
no one has gone before

WHAT REMAINS TO BE DISCOVERED
By John Maddox, Macmillan, 20, ISBN 0 333 65008 5

The title of this book is memorable in more ways than one. Drop the
first word, and we're in Agatha Christie territory. The association is
not altogether facetious, for John Maddox is concerned with the biggest
of all whodunnits - the Locked Universe Mystery, and mankind's
never-ending attempts to solve it.

A few years ago, in a television programme which also featured the late
Carl Sagan, I was privileged to ask Stephen Hawking the question: does
the sequence of ever-smaller entities - molecule, atom, nucleus, quark
- continue indefinitely, or is there a limit, when we finally reach
something as indivisible as the atom was once thought to be? I was not
sure that I would be able to understand his answer, as I stopped
reading about nuclear physics when what are laughingly called
fundamental particles began to exceed the number of elements.

Dr Hawking answered that there probably is a basic structure to the
universe, below which nothing exists, and that it obeys a fairly simple
theory, adding: "I only hope we are smart enough to find it."

This is the sort of question that John Maddox discusses, and after more
than 20 years as editor of Nature, the world's premier science journal,
he is in a unique position to survey the current field of human
knowledge. He has seen scientific fashions come and go, and - unlike
Stephen Hawking - is quite sceptical about "Theories of Everything".

As he demonstrates, scepticism - or at least caution - is advisable
even in areas where science seems to have said the last word. For
example, Wegener's theory that the continents might once have all been
joined together was regarded for decades as total nonsense. "The only
time," one scientist wrote in his memoirs, "I have ever seen a man
literally foaming at the mouth, is when I mentioned continental drift
to a distinguished geologist." Yet through its modern incarnation as
plate tectonics, this heresy has become a key to our understanding of
Earth's early history.

It has been said that any new and revolutionary idea goes through four
stages: (1) "It's crazy"; (2) "It may be true, but it's not important";
(3) "I said it was a good idea all along"; and finally, (4) "I thought
of it first". Unfortunately for Wegener, who compounded his felony by
being a meteorologist and not a geologist, he never lived to enjoy
even stage three.

What Remains to be Discovered opens with a lengthy introduction - "The
River of Discovery" - which makes the point that "modern" science is
only 500 years old, and at the close of every century it seemed to many
philosophers that their world picture was essentially complete, apart
from minor details that would soon be filled in. At least, there would
be no more surprises.

It has been famously said that we learn nothing from history, and this
is amply demonstrated by the fact that voices are now being heard
echoing this same point of view. But John Maddox cautions: "Despite
assertions to the contrary, the lode of discovery is far from worked
out. This book provides an agenda for several decades, even centuries,
of constructive discovery that will undoubtedly change our view of our
place in the world as radically as it has been changed since the time
of Copernicus."

Although centuries are arbitrary divisions, based on the evolutionary
accident that we happen to have ten fingers, it does seem remarkable
that it was almost exactly 100 years ago that the bottom fell out of
Victorian physics with the discovery of X-rays ("A hoax!" - Lord
Kelvin) and the electron.

The next few years may see a repeat performance: as I read reports of
mysterious astronomical objects and anomalous energy production (aka
"cold fusion" - though often it is clearly nothing of the sort) I have
a distinct "this is where we came in" feeling. And I am reminded of the
legendary Superintendent of the U.S. Patent Office, who near the end of
the last century suggested that his department should be closed because
"there was nothing important left to invent". I say "legendary",
because the story is self-evidently untrue: whoever heard of a
bureaucrat proposing the dissolution of his own fiefdom?

Maddox divides his book into three: "Matter" ("in which the origins of
the universe and matter are explored"); "Life" ("in which the origin of
life is considered as well as biological machinery, the riddle of the
selfish gene, and the next human genome projects"); and "Our World"
("in which the nature of our brain is explained, as well as our
greatest invention, mathematics").

As a comprehensive account of the current world view (and its
deficiencies), this book could hardly be bettered, and makes a
convincing point that any limits to discovery - if indeed they exist -
still lie far in the future. But the haunting question remains: are
there limits to human understanding? In almost any field of science, it
now takes most of a lifetime to reach the frontier of knowledge. The
inevitable result will be extreme specialisation, when countless
experts will know everything about nothing. This may be the final
century of the polymath; perhaps the last specimen of that once
flourishing species may have been J. B. S. Haldane, who died in 1964.

No self-respecting reviewer can sign off without picking some nits, and
there is a major understatement in footnote four - repeated, though
with typos which might baffle non-mathematical readers, in footnote 22.
The Pythagoras equation a + b = c does not have merely "several"
integral solutions: it has what is known in the profession as a
countably infinite number.

Trust me . . .

Arthur C. Clarke's latest book, 3001, is published by Voyager,
priced 5.99.

Copyright 1998, Times Newspapers Ltd.

===============
(5) THE PROBLEM OF CONFIRMING THE IMPACT ORIGIN OF SMALL CRATERS

C. Koeberl*), W.U. Reimold, S.B. Shirey: The Aouelloul crater,
Mauritania: On the problem of confirming the impact origin of a small
crater. METEORITICS & PLANETARY SCIENCE, 1998, Vol.33, No.3, pp.513-517

*) UNIVERSITY OF VIENNA,INST GEOCHEM,ALTHANSTR 14,A-1090 VIENNA,AUSTRIA

The impact origin of small craters in sedimentary rocks is often
difficult to confirm because of the lack of characteristic shock
metamorphic features. A case in point is the 3.1 Ma Aouelloul crater
(Mauritania), 390 m in diameter, which is exposed in an area of
Ordovician Oujeft and Zli sandstone. We studied several fractured
sandstone samples from the crater rim for the possible presence of
shock metamorphic effects. In thin section, a large fraction of the
quartz grains show abundant subplanar and planar fractures. Many of the
fractures are healed and are evident only as fluid inclusion trails. A
few grains showed sets of narrow and densely spaced fluid inclusions
trails in one (rarely two) orientations per grain, which could be
possible remnants of planar deformation features (PDFs), although such
an interpretation is not unambiguous. In contrast, an impact origin of
the crater is confirmed by Re-Os isotope studies of the target
sandstone and glass found around the crater rim, which show the
presence of a distinct extraterrestrial component in the glass.
Copyright 1998, Institute for Scientific Information Inc.

============
(6) SCALING ANALYSIS OF METEORITE SHOWER MASS DISTRIBUTION

L. Oddershede*), A. Meibom, J. Bohr: Scaling analysis of meteorite
shower mass distributions. EUROPHYSICS LETTERS, 1998, Vol.43, No.5,
pp.598-604

*) TECHNICAL UNIVERSITY OF DENMARK,DEPT PHYS 307,DK-2800 LYNGBY,DENMARK

Meteorite showers are the remains of extraterrestrial objects which are
captivated by the gravitational field of the Earth. We have analyzed
the mass distribution of fragments from 16 meteorite showers for
scaling. The distributions exhibit distinct scaling behavior over
several orders of magnitude; the observed scaling exponents vary from
shower to shower. Half of the analyzed showers show a single scaling
region while the other half show multiple scaling regimes. Such an
analysis can provide knowledge about the fragmentation process and
about the original meteoroid. We also suggest to compare the observed
scaling exponents to exponents observed in laboratory experiments and
discuss the possibility that one can derive insight into the original
shapes of the meteoroids. Copyright 1998, Institute for Scientific
Information Inc.

=================
(7) MICROMETEORITES FROM ANTARCTICA

C. Engrand*) & M. Maurette: Carbonaceous micrometeorites from
Antarctica. METEORITICS & PLANETARY SCIENCE, 1998, Vol.33, No.4,
pp.565-580

*) UCLA,DEPT EARTH & SPACE SCI,LOS ANGELES,CA,90095

Over 100 000 large interplanetary dust particles in the 50-500 mu m
size range have been recovered in clean conditions from similar to 600
tons of Antarctic melt ice water as both unmelted and partially
melted/dehydrated micrometeorites and cosmic spherules. Flux
measurements in both the Greenland and Antarctica ice sheets indicate
that the micrometeorites deliver to the Earth's surface similar to
2000x more extraterrestrial material than brought by meteorites.
Mineralogical and chemical studies of Antarctic micrometeorites
indicate that they are only related to the relatively rare CM and CR
carbonaceous chondrite groups, being mostly chondritic carbonaceous
objects composed of highly unequilibrated assemblages of anhydrous and
hydrous minerals. However, there are also marked differences between
these two families of solar system objects, including higher C/O ratios
and a very marked depletion of chondrules in micrometeorite matter;
hence, they are ''chondrites-without-chondrules.'' Thus, the parent
meteoroids of micrometeorites represent a dominant and new population
of solar system objects, probably formed in the outer solar system and
delivered to the inner solar system by the most appropriate  vehicles,
comets. One of the major purposes of this paper is to discuss
applications of micrometeorite studies that have been previously
presented to exobiologists but deal with the synthesis of prebiotic
molecules on the early Earth, and more recently, with the early history
of the solar system. Copyright 1998, Institute for Scientific
Information Inc.

====================
(8) SHOCK-INDUCED EFFECTS OF METEORITE IMPACT CRATERS ON EARTH

I. Martinez*) & P. Agrinier: Meteorite impact craters on Earth: major
shock-induced effects in rocks and minerals. COMPTES RENDUS DE L
ACADEMIE DES SCIENCES SERIE II FASCICULE A-SCIENCES DE LA TERRE ET DES
PLANETES, 1998, Vol.327, No.2, pp.75-86

*) IPGP,4 PL JUSSIEU,F-75252 PARIS 05,FRANCE

The basic principles of the physics of shock waves are summarised,
showing how shock pressures, shock and post-shock temperatures, and
shock durations can be estimated in the case of large meteorite impacts
on Earth. In a second part, the pertinence of laboratory high-pressure
dynamic experiments for simulating large meteroite impact events and
for calibrating their physical conditions is discussed. It is concluded
that most shock features are common to natural and laboratory shocks,
although the lifetime of experimental shocked states is shorter by
several orders of magnitude. Then, a review is made of the major shock
effects observed in minerals and rocks. Quartz has been by far, the
most extensively studied shock mineral. particularly, planar
deformation features (PDFs), interpreted as resulting from relaxations
at the shock front, are unambiguous shock indicators, for shock
pressures approximately between 15 and 35 GPa. At higher pressures, the
formation of high-pressure polymorphs of SiO2 in shocked quartz is also
discussed. Shock effects in some other selected minerals, although less
extensively studied, are also reviewed, with special emphasis on the
discovery of diamonds at impact sites and of all the high-pressure
polymorphs of olivines an pyroxenes, including silicate perovskite, in
shocked meteorites. Finally, the controversial links between large
impacts and major environmental effects are discussed in a
fourth part. ((C) Academie des sciences/Elsevier, Paris).

=============
(9) JUPITER'S GREAT INEQUALITY & ASTEROID ORBIT EVOLUTION

S. Ferraz Mello*), T.A. Michtchenko, F. Roig: The determinant role of
Jupiter's Great Inequality in the depletion of the Hecuba gap.
ASTRONOMICAL JOURNAL, 1998, Vol.116, No.3, pp.1491-1500

*) UNIVERSITY OF SAO PAULO,INST ASTRON & GEOFIS,CP 3386,AVE MIGUEL
   ESTEFANO 4200,BR-04301904 SAO PAULO,BRAZIL

This paper deals with the influence of Jupiter's ''Great Inequality''
(GI) on the orbital evolution of 2:1 resonant asteroids. This
perturbation of Jupiter's motion enhances the chaotic diffusion of
orbits and the depletion of asteroids in the Hecuba gap. The failure of
models that adopt for Jupiter an elliptic motion with only secular
perturbations is explained. We also show the dependence of the
diffusion rates on the GI period, and the maximum diffusion rates that
would take place if the GI period were closer to the libration period.
Significant similar effects are absent in the 3:2 asteroidal resonance.
Copyright 1998, Institute for Scientific Information Inc.

================
(10) LIFE FLOURISHED WHEN EARTH WAS WARMER

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

News Services
University of Arizona

Contact(s): Judith Totman Parrish, 520-621-4595,
parrish@geo.arizona.edu

October 14, 1998

Life flourished when Earth was warmer, scientist says

The threat of a global warming doesn't scare Judith Parrish, a
geologist at the University of Arizona in Tucson and an expert on
ancient climates.

She's seen the ghost of the distant past in fossil leaves from the mid-
Cretaceous, about 100 million years ago. These long-dead leaves tell
tales of a warmer climate, when forests grew in the now-barren polar
regions.

"Life flourished when the climate was warmer," said Parrish, UA
professor of geosciences. Her book, "Interpreting Pre-Quaternary
Climate from the Geologic Record," is being released this month. The
Quaternary represents roughly the last 2 million years, a time of
recurring ice ages when continental glaciers sometimes stretched as far
south as Illinois.

"The last 2 million years don't have anywhere near the full range of
climate history," Parrish emphasized. "The lack of ice during the
Cretaceous is typical. Having the great big ice caps is not typical."

The Cretaceous describes the period 113 million to 65 million years
ago, when dinosaurs roamed the planet. Geological evidence indicates
that during the Cretaceous, as during much of the Earth's history, the
planet was much warmer than it is today -- and generally warmer than it
is projected to be in the next few centuries as the result of a buildup
in greenhouse gases.

Some of that evidence comes from Parrish's own research, including a
paper she recently wrote with colleagues on the vegetation found near
the South Pole during the mid-Cretaceous. The team of researchers
traveled to locations in New Zealand to examine sediments and fossils
deposited during the mid-Cretaceous, using methods they had developed
for a previous project in Alaska.

When the fossils were deposited in what are now New Zealand and Alaska,
the land masses under scrutiny were both located at latitudes of
between 70 and 85 degrees -- within the polar circles that are shrouded
in continuous darkness for several months every year. Latitudinal lines
run from the middle of the planet to its tip, starting at 0 degrees
around the equator and continuing to 90 degrees North and South at each
pole.

Yet despite the darkness and polar location, the fossils indicated that
the lands in question supported a thriving forest during the
mid-Cretaceous. Parrish and her colleagues believe the forests
resembled modern-day forests of western Oregon, with a canopy of
cone-bearing trees shading an understory of ferns and horsetails.

Unlike modern pine trees, though, the Cretaceous conifers apparently
shed their leaves every year. Present-day Oregon forests thrive at 45
degrees North but fade into a different forest type by about 50 degrees
North.

"By the time you get up to British Columbia, the diversity of the
understory has dropped," Parrish said. The boreal forest, which ranges
up to about 70 degrees North, has much smaller trees and fewer species,
she noted. "By that time, they're scrawny little things. It's generous
to call them trees."

The size of local plant life tends to increase with warmer
temperatures, given enough water for ample growth. But the shape of the
leaves yields even more information for researchers looking for clues
on past climates. In fact, Jack A. Wolfe, a scientist based at the UA
Desert Laboratory on Tumamoc Hill in Tucson, developed a successful
method for estimating annual average temperature of a region by
comparing leaf shapes of local plants.

Parrish and her colleagues applied Wolfe's technique to their polar
forests. The results? They estimated that the average annual
temperature around the poles during the mid-Cretaceous was about 10
degrees Celsius, or roughly 50 degrees Fahrenheit.

Yet the warmer poles did not necessarily mean hotter tropical climates,
as Parrish points out. Other researchers have found evidence for
relatively stable temperatures in the lower latitudes around the
equator when comparing the Cretaceous to modern times.

"When you have global change, the action is in the higher latitudes,"
Parrish explained. Computer models today predict most of the 2 to 7
degree Fahrenheit warming expected over the next century will also be
centered on the poles rather than tropical regions.

There is at least one consequence of a future warming that could
adversely affect many people, however: Sea level is expected to rise by
as much as 3 feet over the next century as water trapped in continental
ice melts into the ocean and inundates coastal cities.

"It's more a social problem than anything else," Parrish said of the
perceived threat of global warming. "It's just that 80 percent of the
population has chosen to live near coastal areas."

LINKS:
http://www.geo.arizona.edu/

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