PLEASE NOTE:


*

CCNet 38/2001 - 9 March 2001: REACTIONS TO THE HOUSE OF LORDS DEBATE
--------------------------------------------------------------------


"I would personally much hope that an international ad-hoc group is
soon created to discuss the Europe-wide prospects and if possible,
to come up with an overall plan that could help Europe to assume its
proper role also in this kind of research, together with the USA and
Japan. We are certainly still interested in discussing the possibilities of
hosting a major southern NEO facility at one of our observatories in
Chile."
--Richard West, European Southern Observatory, 8 March 2001


"While the IMPACT programme has a main focus on the study of impact
craters on Earth and the effect of impact events on the geo- and
biosphere, one of the topics of concern is of course the source of the
impacting objects (NEOs and comets). In this regard, the current
debate of the UK Government Task Force Report is of great interest to the
IMPACT programme (and, hopefully, vice versa). The contribution from
our side to the debate is obvious and two-fold: on the scientific side, a
definition of the impact flux from geological studies and data on the
effects of impact events; on the organisational side, we have in place a
large group of researchers in Europe (and elsewhere), mainly from the
geoscience and planetary science community, who are concerned of, and
interested in, impact events. As such, our community will certainly
be happy to interact in the current debate."
--Christian Koeberl, Chairman, ESF IMPACT programme, 8 March
2001


"The need for the UK (and other nations) to have a centre for prompt
information on NEOs is marvelously illustrated by actual events. The Lords
debate on March 7th clearly took place with no-one present being aware that
there was a relatively-near miss of the Earth by a substantial (circa 1
km) asteroid on February 27th, that object not being discovered until
March 3rd, well after its closest approach at just within 0.01 AU (about
four times the lunar distance). This was public knowledge if people knew
where to look at least from March 6th, and between discovery and the
release of MPEC 2001-E17 fifteen observatories had obtained astrometry
on this quite bright object. What is one to make of claims that the UK is a
leading nation in Europe in this field, when one sees that astronomers in
several European countries had tracked this asteroid within a few
days of its discovery by the LINEAR team in the USA, but there was no UK
contribution to these efforts?"
--Duncan Steel, University of Salford, 8 March 2001


(1) EUROPEAN SOUTHERN OBSERVATORY INTERESTED IN INTERNATIONAL NEO
CO-OPERATION
    Richard West <rwest@eso.org>

(2) VIEWS OF THE ESF "IMPACT" PROGRAM ON THE NEO ISSUE
    Christian Koeberl <christian.koeberl@univie.ac.at>

(3) A VIEW FROM SPACEGUARD UK
    Jonathan Tate <fr77@dial.pipex.com

(4) THE HOUSE OF LORDS DEBATE: FORWARD STEPS & BACKWARD SLIPS
    Duncan Steel <D.I.Steel@salford.ac.uk>

(5) 'QUICK' DEMISE FOR THE DINOSAURS SUBSTANTIATES CATASTROPHIC KILLER
IMPACT
    BBC News Online, 8 March 2001

(6) REJOICE: "COSMIC SMACK ENCOURAGES LIFE TO GO FORTH AND MULTIPLY"
    Ron Baalke <baalke@jpl.nasa.gov

(7) MUTANT SPACE FUNGUS IS BOGUS, EXPERTS SAY
    UPI, 7 March 2001

(8) COMPELLING EVIDENCE FOR P/T KILLER IMPACT
    Hermann Burchard <burchar@mail.math.okstate.edu>

(9) COMETARY IRIDIUM AND THE P-T BOUNDARY QUESTION
    Andrew Glikson <geospec@webone.com.au>

(10) DATING IMPACT CLUSTERS
     S. Fred Singer <singer@sepp.org>

(11) CARL SAGAN
     Duncan Steel <D.I.Steel@salford.ac.uk>

================

(1) EUROPEAN SOUTHERN OBSERVATORY INTERESTED IN INTERNATIONAL NEO
CO-OPERATION

From Richard West <rwest@eso.org>

Dear Benny,

Thank you for your kind invitation to comment. We have of course been
following the recent developments with some interest - and I just received
information about the debate at the House of Lords from Harry Atkinson.

I do not think that I can contribute much at this moment except saying that
the emphasis on the international aspect clearly is very central to the next
developments. I would personally much hope that an international ad-hoc
group is soon created to discuss the Europe-wide prospects and if possible,
to come up with an overall plan that could help Europe to assume its proper
role also in this kind of research, together with the USA and Japan.

We are certainly still interested in discussing the possibilities of hosting
a major southern NEO facility at one of our observatories in Chile.

Kind regards,

Richard

--
Richard West                              e-mail: rwest@eso.org
ESO Education and Public Relations Dept.  Tel +49-89-32006276
Karl-Schwarzschild-Strasse 2              Fax  +49-89-3202362
D-85748 Garching (Germany)

=========
(2) VIEWS OF THE ESF "IMPACT" PROGRAM ON THE NEO ISSUE

From Christian Koeberl <christian.koeberl@univie.ac.at>

Dear Benny,

As many of you know, the European Science Foundation (ESF) is coordinating
and financing a scientific programme with the title "Response of the Earth
System to Impact Processes" (IMPACT). This programme is an interdisciplinary
programme aimed at understanding impact processes and
their effects on the Earth System, including environmental, biological, and
geological changes, and consequences for the biodiversity of ecosystems. The
goals of the programme, and details about our acitivities, can be found on
our web page <http://pssri.open.ac.uk/ESF/>.

The IMPACT programme has currently 15 member nations from all over Europe.
The activities of the programme range from workshops to specific topics
regarding impact cratering, short courses on impact stratigraphy, shock
metamorpism, etc., mobility grants for  students and young researchers,
development of teaching aids, and publications.

The programme deals with three main areas of research:

-- The Impact Event: Knowledge of the physical and chemical constraints of
the impact process is still limited. Differences between impacts in a
continental versus a marine environment need to be assessed, as well as a
better understanding of the astronomical background (i.e., the population of
earth orbit crossing asteroids and comets). This topic includes issues of
potential importance for the Earth's climate, such as shock-degassing of
carbonate- and sulfate-bearing rocks.

-- Energy Transfer to the Environment: The mechanism of how the enormous
energy that is released during an impact event is actually transferred to
the atmo-, hydro-, bio-, and geosphere is probably the least understood part
in the chain that may link impact events with environmental changes.

-- Short- and Long-Term Effects on the Environment: Once the impact energy
is imparted onto the Earth System, the response of the environment needs to
be studied. This section includes various topics, such as the formation of
economically important mineral deposits. Regional to global long-term
effects may include climatic consequences, which are badly understood and
require extensive computer modeling. Effects on the biodiversity of
ecosystems are not restricted to impact-related extinctions, but may also
involve an increase in biodiversity.

This listing shows that, while the IMPACT programme has a main focus on the
study of impact craters on Earth and the effect of impact events on the geo-
and biosphere, one of the topics of concern is of course the source of the
impacting objects (NEOs and comets). In this regard, the current debate of
the UK Government Task Force Report is of great interest to the IMPACT
programme (and, hopefully, vice versa). The contribution from our side to
the debate is obvious and two-fold: on the scientific side, a definition of
the impact flux from geological studies and data on the effects of impact
events; on the organisational side, we have in place a large group of
researchers in Europe (and elsewhere), mainly from the geoscience and
planetary science community, who are concerned of, and interested in, impact
events. As such, our community will certainly be happy to interact in the
current debate.

From my point of view, two main aspects will be important:

1) based on our knowledge of the effects of impact events, the definition of
the social implications of impact events on Earth of various size and
destructive power (e.g., effects on agriculture, short-time climatic
effects, economical effects); this could be done in comparison with other,
similarly catastrophic natural desasters;

2) to take advantage of the momentum gained from the UK Task Force Report to
advance our astronomical knowledge of NEOs on a European and global level.
As with many other scientific undertakings, relatively small amounts of
money would go a long way (a comparison to funds used for various, currently
especially in the UK much debated animal diseases that affect meat eaters
would boggle the mind). What is necessary is the political will to do
something.

Christian Koeberl
University of Vienna
Chairman, ESF IMPACT programme

Institute of Geochemistry
University of Vienna
Althanstrasse 14
A-1090 Vienna, AUSTRIA

Tel.: +43-1-4277-53110
Fax: +43-1-4277-9531
e-mail: christian.koeberl@univie.ac.at
Web: www.univie.ac.at/geochemistry/

==============
(3) HOUSE OF LORDS DEBATE: A VIEW FROM SPACEGUARD UK

From Jonathan Tate <fr77@dial.pipex.com

Benny,

I am delighted to say that the debate in the House of Lords, led by the Lord
Tanlaw, was significantly more enlightening than the original government
response to the NEO Task Force report. I will not go into the details as you
have already published the transcript, but a number of points deserve
emphasis.

Firstly, Lord Tanlaw's opening speech was masterful, and he, with his
colleagues Lord Hunt of Chesterton and Lord Razzall displayed a clear
understanding of the issues. They all made very useful, constructive
suggestions to the science minister, Lord Sainsbury. They also made it
perfectly clear that they intend to hold the government's feet to the fire
over the follow-up report that has been promised for "later in the year". A
cynic may wonder whether this means this year or next, given the "at the
turn of the year" promise for the original government's response, but the
BNSC has been thumped enough over the past few weeks to allow more
prevarication.  I doubt whether the noble Lords will have much patience
either!

In his reply, Lord Sainsbury made a couple of interesting comments. In
answer to the question of funding, he stated that "we have no extra funds
for these activities. They will have to compete with the activities which we
already undertake in the field of space and astronomy. It is worth making
the point that we spend considerable sums on astronomy. In that context it
seems not inappropriate to direct a modest amount to determine whether any
asteroid or comet could endanger us."  This means two things. Firstly the
dedicated funding line that has always been considered as essential will not
be forthcoming - NEO studies will have to compete with other astronomical
projects. This arrangement fails to recognise the unique and
multi-disciplinary nature of the impact hazard that has been emphasised in
all of the briefing material that has been flying around. Secondly though,
this statement is a wake-up call to funding agencies such as PPARC hopefully
saying "do not ignore this issue - we (the government) will be watching."

The poor old BNSC received the ritual "bashing" (justified or not), but the
minister stated that "The British National Space Centre has considerable
expertise in this area". Mmmmm, interesting.

On the key issue of the UK NEO Centre Lord Sainsbury stated that: "the
Government plan to set up a facility whose role would be to act as a
showcase for the public on near earth object issues. The facility should
provide a clear and objective introduction to the topic and in the process
further the Government's wider aim of increasing public understanding of
topical science issues."

The Spaceguard Centre will do just that. I hope that the BNSC realise that
there is a resource there that they can use and co-operate with. If
co-operation fails, it will not be the fault of the Spaceguard Centre.

Then came an interesting statement: "I do not think we should simply decide
that one body, even if it is as distinguished as the one at Armagh, should
do this job. It would be better to introduce competition. We should seek
advice not from one body but from all the best experts around the world." I
am not sure what this means. The whole idea is to have a single
co-ordinating organisation that can draw together all of the threads into a
coherent, understandable picture. Looks like another job for the Spaceguard
Centre.

Lord Sainsbury finished by telling the noble Lords that: "I can assure the
House that the Government attach the highest importance to taking this work
forward." This is good, and Lord Sainsbury has clearly "gone the extra mile"
in political terms. He should be congratulated for this. He is clearly a man
of vision and political courage. It seems to me that any backsliding that
has, and will be caused by the bureaucrats, but with a sufficient spike in
the rear, such as that delivered by Lord Tanlaw and his colleagues, such
prevarication can be overcome.

So, where do we stand?

Plusses:

* Clear government commitment.
* Meaningful dialogue within Europe and other international forums.
* Studies into hardware for NEO research.
* Significant support from key people.
* BNSC as lead department.

Minuses:

* No decisions on action as opposed to talk.
* A further delay in decision making (later in the year?)
* No independent funding.
* Reliance on normal funding agencies for resources.
* Dilution of the NEO Centre concept.
* BNSC as lead department.

Jay

=============
(4) THE HOUSE OF LORDS DEBATE: FORWARD STEPS & BACKWARD SLIPS

From Duncan Steel <D.I.Steel@salford.ac.uk>

Dear Benny,

The level of good information - and the lack of giggles - in the recent NEO
debate in the House of Lords is to be welcomed. Unfortunately the IAU naming
rules for asteroids (minor planets) preclude the possibility that any might
obtain a moniker from a politician. If that was the only matter found to
jest about, however, then that is an excellent sign.

This has to be regarded as another forward step, albeit with a few backward
slips. It is clear that the Government still does not understand that the
phenomenology of NEO discovery and tracking is not science in itself, and so
cannot expect to command funding in a competitive science marketplace. On
the other hand, the recognition that this is a job for the government,
rather than private sponsorship, is welcome.

The need for the UK (and other nations) to have a centre for prompt
information on NEOs is marvelously illustrated by actual events. The Lords
debate on March 7th clearly took place with no-one present being aware that
there was a relatively-near miss of the Earth by a substantial
(circa 1 km) asteroid on February 27th, that object not being discovered
until March 3rd, well after its closest approach at just within 0.01 AU
(about four times the lunar distance). This was public knowledge if people
knew where to look at least from March 6th, and between discovery and the
release of MPEC 2001-E17 fifteen observatories had obtained astrometry on
this quite bright object. What is one to make of claims that the UK is a
leading nation in Europe in this field, when one sees that astronomers in
several European countries had tracked this asteroid within a few days of
its discovery by the LINEAR team in the USA, but there was no UK
contribution to these efforts?

In view of this, one must hope that real action rather than simple rhetoric
is to come soon. This is certainly what the several speakers in the Lords'
debate were pressing for, and Lord Sainsbury's reply promised that action is
in the pipeline.

Duncan Steel

=============
(5) 'QUICK' DEMISE FOR THE DINOSAURS SUBSTANTIATES CATASTROPHIC KILLER
IMPACT

From BBC News Online, 8 March 2001
http://news.bbc.co.uk/hi/english/sci/tech/newsid_1209000/1209870.stm

New research suggests the fearsome creatures could have been wiped from the
face of the Earth in as little as 10,000 years.

The evidence comes from a study of rocks in Italy and Tunisia. The work
lends support to the idea that a single, giant impact of an asteroid or
comet was responsible for the mass extinction of life that occurred 65
million years ago.

In so doing, the research also undermines the popular, alternative theory
for the demise of the dinosaurs: climate change brought on by huge volcanic
eruptions.

Geological timeline

Sujoy Mukhopadhyay and colleagues studied sedimentary rocks that mark the
so-called K-T boundary, the line of separation between the zones of
geological time referred to as the Cretaceous period and the Tertiary
sub-era.

It is at this K-T boundary, timed at about 65 million years ago, that 70% of
all life, including the dinosaurs, suddenly disappears from the fossil
record.

But scientists have struggled to determine how long the deposition of the
clay minerals that make up the K-T boundary lasted - and by inference how
long it took to kill off the dinosaurs. It would also indicate how long it
took for life to turn the corner - the end of the boundary shows the
beginnings of a recovery.

Mukhopadhyay's US-Italian team believe they can now measure the length of
this dark period in Earth history.

Interplanetary dust

They analysed the amount of helium-3 in the rocks of the K-T boundary.

Levels of this type, or isotope, of the element reflect the amount of
interplanetary dust that settles on Earth and, properly calibrated, can be
used as a tool to time the rate at which rocks are laid down.

"If you can show that the flux is not changing, you can use it as a marker
to figure out how quickly sediments are depositing," Sujoy Mukhopadhyay,
from the California Institute of Technology, told BBC News Online.

The research suggests the K-T boundary was deposited in about 10,000 years.
He said the short period lent support to the theory that the dinosaurs were
wiped out in a sudden, catastrophic event such as the impact of an
extraterrestrial body.

Single impact

The constant rate of accumulation of helium-3 also indicates that the
impactor was not part of a comet shower or bombardment.

"Comets are dusty objects and if you have several comets coming into the
inner Solar System, you will increase the dust flux to the Earth,"
Mukhopadhyay said.

"If you increase the dust flux, you increase the helium-3 flux. And so if
you don't see an increase in the helium-3 in these sediments, it rules out a
large number of comets coming in."

Scientists think they know where the suspected asteroid or comet came down.
Several studies have now detailed traces of a crater beneath the Yucatan
Peninsula in Mexico.

'Smoking gun'

Even so, some scientists still hold to the theory that massive volcanic
eruptions at about the same time were a more likely cause for the end of the
dinosaurs.
 
The Deccan Traps, the flood basalts of western India, are often cited as the
alternative "smoking gun" for the death of the dinos.

Certainly, this type of volcanism would have had a major effect on global
climate, and probably did disrupt the food chains upon which much life
depended, but Mukhopadhyay said the event occurred over too long a period.

"The Deccan Traps erupted over much longer timescales - over 500,000 years
or more. If the recovery of life starts after only 10,000 years, it is hard
for us to see how the traps are influencing the mass extinction."

The helium-3 research is published in the journal Science.
 
Copyright 2001, BBC

==========
(6) REJOICE: "COSMIC SMACK ENCOURAGES LIFE TO GO FORTH AND MULTIPLY"

From Ron Baalke <baalke@jpl.nasa.gov

http://www.space.com/scienceastronomy/solarsystem/impact_rebound_010309.html

Cosmic Smack Encourages Life To Go Forth and Multiply
By Robert Roy Britt
space.com
08 March 2001

A discovery that earthly flora and fauna rebound and advance rapidly after
catastrophic collisions by space rocks highlights the resourcefulness of
life and bolsters a growing suspicion that evolution does its best work in
extreme crises.

When a comet or asteroid smacked Earth 65 million years ago, the dinosaurs
bid farewell. They could not adapt to a world remade by the extreme
ecological violence. They were not alone. Roughly two-thirds of all life on
Earth vanished.

But new species sprang forth from the catastrophe, evolving quickly to fill
new niches of climate, water and soil conditions. A new study examined
extraterrestrial dust to pin down just how quickly.

Full story here:
http://www.space.com/scienceastronomy/solarsystem/impact_rebound_010309.html

=========
(7) MUTANT SPACE FUNGUS IS BOGUS, EXPERTS SAY

From UPI, 7 March 2001
http://www.vny.com/cf/News/upidetail.cfm?QID=165942

Mutant space fungus is bogus, experts say
By CHARLES CHOI, UPI Science Writer

WASHINGTON, March 7 (UPI) -- "Fanciful" is what U.S. space scientists are
calling the notion that a mutant space fungus may threaten Earth when Mir is
brought down later in March.

They point out humans have lived aboard the aging space station for months
without effects -- and besides, what the heat of descent doesn't kill, the
salt water the wreckage lands in will, they say.

In a press conference in Moscow on Tuesday, Russian space program expert
Yuri Karesh warned that fungus festering aboard Mir may have mutated into a
threat. Once the space station falls to Earth between March 17 and 20, he
said the space organisms could prove toxic.

"A realistic problem exists," Karesh warned. Karesh, who has undergone
cosmonaut training, became concerned over the space fungus after reviewing
Mir documents at Moscow's Institute of Medical and Biological Problems.

However, John Rummel believes the idea of space fungi mutating into
something significantly different from fungi on Earth is "fanciful," said
the NASA planetary protection officer.

"Cosmonauts and astronauts have been up to and down from Mir all the time,
and there's no indication that they've faced any different problems
different from normal earth fungi," Rummel told United Press International
from NASA headquarters in Washington. "Problems on Mir are reasonably well
known. I don't think that conditions on Mir are any more dangerous than they
are on Earth."

Fungus infests damp places aboard the orbiter -- under control panels and in
air ducts -- and corrodes equipment with acid. While most of Mir will
incinerate when the 137-ton station de-orbits, hundreds of fragments are
expected to survive reentry and perhaps insulate fungus from the tremendous
heat.

"It's the same sort of thing with meteorites," said James Staley, director
of the National Science Foundation's astrobiology program. "We know in some
cases there are areas within a meteorite where temperatures wouldn't get so
high that they would cause sterilization."

Staley feels that even if any fungi survive the fall into the southern
Pacific, they probably will not live through the swim.

"Most fungi are not marine," he said. "They would not be able to grow in the
high salt concentrations. They might remain viable for some length of time,
but they would ultimately die."

It is possible the orbiter debris will collide with land masses such as
Australia, or that fungi that fell in the ocean could survive long enough
for wind or ocean currents to deposit them on land, Staley added. Still, he
said that the space fungi would have a lot of competition with other
microorganisms.

"Actually, they're from Earth," Staley said. "I think there is a tendency to
exaggerate. I don't view these as being any great hazard to Earth life."

Copyright 2001 by United Press International.
All rights reserved.

============================
* LETTERS TO THE MODERATOR *
============================

(8) COMPELLING EVIDENCE FOR P/T KILLER IMPACT

From Hermann Burchard <burchar@mail.math.okstate.edu>

Dear Benny,

compelling evidence for a P/Tr killer impact can now be given.  The main
argument offered will be that alternative explanations of localized flood
basalts other than by impact are not credible.

By non-localized eruptions are meant the planet-wide spreading zones or
mid-ocean ridges.  Hence a localized basalt eruption is a marker of an
impact at or near the site.  I.o.w., local basalt eruptions, not those near
spreading ridges, are routinely associated with cosmic killer impacts, and
in fact amount by themselves to proof of impact.

Plumes involved in the eruptions later migrate in directions opposite to
motion of crust and upper mantle as these shift positions within the plate
tectonic scheme. Smaller ones die out after fairly brief periods. As an
example, A. & E. Tollmann, both expert geologists, in "Sintflut", their
(under-appreciated) book, report on possible volcanism in connection with
the 20 km Ries impact crater to the SE at a distance of about 100 km
center-to-center.  At a typical rate of about 40 mm/a we obtain a life time
of the plume of 2.5 Ma. Wysession [see my Mar 7 CCNet note] reports the
plume causing the Deccan traps now has migrated to volcanic Reunion
Island in the Southern Indian Ocean.  Maps of the seafloor clearly show the
track, from near Bombay straight south, due to the northward shift of the
Indian plate.  The site off the Indian coast where the track begins is in
the vicinity of the giant Shiva crater.  The plume apparently has lasted for
65 Ma.

An erroneous rising plume theory would prefer terrestrial-endogenous causes
over cosmic ones.  An "impact-genetic plume" theory is espoused as opposed
to this "rising plume" theory. Two kinds of rising plumes have been
proposed: Short-lived or transient, and long-lived ones. It is suggested
that transient plumes result from small impacts and long-lived ones from
large cosmic bodies striking the planet. By the way, samples of all four of
these theories have recently been seen on CCNet, thanks in large part to
Michael Paine, who diligently collected them from various geology
conferences. The paper by Bradford H. Hager (Linda T. Elkins Tanton,
presenter) details a viable model for giant impact craters giving rise to
flood basalts.  This is remarkably similar to suggestions I made in recent
notes to CCNet, although the abstract does not mention phase transitions due
to reduced pressure in the upper mantle.

It is now shown that the endogenous theory is not well motivated. Rising
plumes will be out, impact plumes in.  The proof proceeds in six steps, 0 -
5.

0.  The basic premise of the rising plume theory is of the mantle being
heated from below by a hot core.  This is how deep mantle convection is
powered: NO HOT CORE - NO DEEP MANTLE CONVECTION.  Now it emerges that
density constraints prohibit a core rich in actinides, and chemical
segregation explains the lithophiles Uranium and Thorium are enriched in the
crust, dispersed less abundantly in the mantle, but absent from the core
which accepts only siderophiles.  Hence the heat flowing from the core is
primordial (=potential gravitational energy converted to heat by
condensation of numerous planetesimals into planet Earth).  Today, there
still is some iron condensing in the liquid outer core and falling into the
solid inner core, and some Potassium 40 may be exptected in the outer core.
However if this energy source were the only one then Earth would be no more
thant 100 Ma old, and by now reduced to "frozen cinder".

1.  Transient (short-lived) rising deep mantle plumes causing flood basalts
are not credible.  Extremely slow movement in a highly viscous lower mantle
prevents this. That leaves long-lived plumes originating at billion year
time scales along the core-mantle boundary. I suppose this is where the
"fingerlings" come in: Wiggling upward these are thought to look for an
accomplice impactor to make a plume.

2. Evidence from seismic tomography for _ANY_ lower mantle circulation is
unconvincing.  Tomography is mathematically a rank-deficient least squares
procedure(*).  Early applications in surgery, for example, were beset with
horrible "ghost" tumors appearing all over a patient's skull or body cavity.
Today, surgeons can rely on extremely clever proprietary software, to my
knowledge, specifically designed to overcome these problems.
- - - - - -
Footnote (*) I.e., in the singular value decomposition of the discretized
Radon transform small singular values cause trouble. As this is math I
should hedge a little bit. There may be versions of CAT that do not lend
themselves to being described as rank-deficient least squares. This is a
large, powerful, beautiful, mathematical theory, akin to Fourier Analysis,
which in fact is one way to study it.  Trouble arising is best seen in
theorems relating to infinite dimensional operator theory versions where it
is proved that the same or nearly the same images can be created by very
different internal density functions. Seismic tomography is new to me. This
seems to be related to or a version of diffraction tomography, different
from X-ray tomography but presumably as difficult to implement reliably.
 - - - - - -

3. Lower mantle seismic velocities are almost uniform. You are trying to
find a tumor made of tissue nearly indistinguishable from healthy one. Even
with the most clever software, this would get you to see "ghost tumors". I
doubt that fingerlings even if real could be seen, and if seen, would be
real. I promise to look for contrary evidence.

4. One argument offered for deep mantle circulation are higher seismic
velocities in the lower mantle beneath old subduction zones. An alternate
explanation is also mentioned:  Chilling of lower mantle over time > 100 Ma
by contact with subducted crust [see Wysession, in my Mar 7 CCNet Note, for
the full discussion]. The alternate argument prevails, and there is then no
need to postulate deep mantle circulation, because in a rigid mantle with
super-high viscosity billion-year time scales motion at high plate tectonic
speeds is excluded.

5. The final straws for which rising plume theory grasps are anti-continents
seen at the core-mantle boundary. Due to the problems with seismic
exploration cited above, we must relegate these anticontinents to the same
status given to ghost-tumors: Artifacts of procedure. There simply are no
credible theories offered for dynamic coupling between crust and core-mantle
boundary at the needed plate-tectonic rate.

Historical Note.  When Robert Dietz identified Sudbury as an astrobleme or
impact scar during a nine day field exploration in 1961, he gave an eloquent
description of the local geology as what he called the "...ore hosting
sublayer .. a splash emplaced target/bolide melt lining Sudbury Basin like
spackle in a bowl .. also injected centrifugally into tensional cracks..."
[1991, see my Feb 19 CCNet note].  He then added that Noril'sk was a
"Sudbury look-alike".  His diagnosis was apparently not widely accepted,
why?  We may seek the motivation in a rival rising plume theory, to the
effect that local basalt eruptions happen when a plume, born in one way or
another near the core-mantle boundary, mushrooms up, reaches the
lithosphere, and breaks through the crust.  I suggest that this long-lived
bloom of a theory after mushrooming through the strata of geology for
decades ought now be recognized as a falsified hypothesis.

For more on impact generation of plumes and on a compatible theory of
non-local (ridge) eruptions, see my earlier notes to CCNet.

Regards,

Hermann Burchard

=============
(9) COMETARY IRIDIUM AND THE P-T BOUNDARY QUESTION
 
From Andrew Glikson <geospec@webone.com.au>

Dear Benny,
 
I refer to D. Hughes' comment on my CCNet communication (CCNet 07-03-01),
where he states "How does he (AG) know? What is his evidence? Who told him?
What does he think cometary dust is made of? How does he think the general
compositions of cometary dust differs from that of the composition of
asteroids?". 
 
The answer to these queries lies in Hughes's own statement "Typically about
30 % of the mass of a comet is in the form of dust". Unless a novel
composition is proposed for cometary silicates, a chondritic composition is
generally assumed (500+/-100 ppb Iridium, cf. McDonough and Sun, 1995, Chem.
Geol. 120, 223-253). Depending on the proportion of cometary silicate dust
to ices (for example H2O, NH3, CH4, and their breakdown products spectrally
measured in cometary tails), the amount of Iridium released by a cometary
impact will be diluted relative to an asteroidal impact of the same mass -
hence an expected weaker Ir signature in impact fallout deposits
corresponding to a cometary oceanic impact model for the P-T boundary.
 
As to the question "Who told him?" - I refer Hughes to relevant reviews (for
example - Dickinson, T. The Universe and Beyond. Camden, 1986; Lovell et
al., The Guide to Modern Astronomy. Cambridge, 1987;  Sagan, C., Cosmos.,
Ballatine, 1985; Harwit, M., Cosmic Discovery. MIT, 1984; Moore, P. The New
Concise Atlas of the Universe, Crown) and original papers too numerous to
cite here.
 
I am glad to note the emerging consensus regarding the question of the
origin of the P-T extinction, where comments by I. Gilmour ("The evidence
for an impact having caused a second mass extinction must be subjected to
the same degree scrutiny (as for the K-T) and must be just as convincing" -
CCNet 06-03-0), Benny Peiser's comment ("But as long as more compelling
evidence will emerge as a result of further research, the theory remains
hypothetical, and even unconvincing to the rigorous sceptic." CCNet
07-03-01) and my own comment ("the jury is still out" - CCNet 07-03-01).  It
would appear the differences are mainly semantic.
 
Andrew Glikson
Australian National University
08-03-01

===========
(10) DATING IMPACT CLUSTERS

From S. Fred Singer <singer@sepp.org>

Dear Benny

Apropos the Glikson letter of March 7

Has anyone compared the dates of clustering of impact craters with
cosmic-ray ages of meteorites (that would define the breakup of a parent
body)? I would appreciate literature references.

Sincerely

S. Fred Singer, President
Science & Environmental Policy Project
http://www.sepp.org

=======
(11) CARL SAGAN

From Duncan Steel <D.I.Steel@salford.ac.uk>

Dear Benny,

Rather than leaving it to our trans-Atlantic colleagues to leap to the
defence of their late compatriot, I think it might be best to point out
immediately an unfortunate choice of words in the debate in the House of
Lords. The passage to which I refer is this:

"the comments of the science fiction writer, Carl Sagan..."

Technically that statement is correct, in that Sagan did write the novel
'Contact' on which the motion picture of the same name was based, but in the
context used this would be rather like remembering Sir Winston Churchill
solely as a promoter of cigars. I certainly do not want to denigrate in any
way the significance of science fiction writers in this context, and note
with pleasure the mention of Bill Napier's novel 'Nemesis' in that debate -
it is a shame that Sir Arthur C. Clarke's 'Rendezvous with Rama' was not also
mentioned, given its 'Spaceguard' connection - but Sagan should not be described
merely in that way. He was a first-rate research scientist, a brilliant teacher, a
wonderful exponent of science, a bitter foe of pseudo-science,
and a science (fact) writer too. Given the need for the promotion of the
public understanding of science, and Sagan's example as a scientist
understanding the public, it would be inappropriate if he were categorised
purely on the basis of the novel and movie with which he was connected. It
is also worth noting that although he (with Steve Ostro, Al Harris and Greg
Canavan) highlighted what is termed the 'Deflection Dilemma', correctly
pointing out the inherent danger of developing an NEO interception and
deflection system prior to the possible identification of an actual
impactor, Sagan was also a very strong supporter of the need for an
immediate, comprehensive NEO surveillance programme, with international
involvement.

Duncan Steel


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