PLEASE NOTE:


*

CCNet, 12 November 1999
------------------------------


     POEM OF THE DAY

     By Malcolm Miller
     stellar2@actonline.com.au

     LEONIDS

     Speeding specks of unknown stuff might light the sky,
     diverging in silent lines, some short, some long,
     across clear skies in thousands, spectacular beyond belief
     when at their best. In quieter years, those in the know
     huddle warm wrapped, eyes on the sky, seeing what happens
     when velocity's vast energy's converted into heat.
     Perhaps their greatest lesson is that space is hazardous,
     it has its storms and reefs as well as any ocean,
     the shoals and rocks of space that every navigator
     must heed to come safe home from voyaging.
     Six hundred tiny vessels circle endlessly this island Earth,
     as vital to our trade as any caravel of Spain in ages past;
     it may be that a few will founder in the Leonids brief hurricane,
     but from their loss we'll learn to make our space ships safer.

     MM 12.11.99



(1) 200 POTENTIALLY HAZARDOUS ASTEROIDS
    http://cfa-www.harvard.edu/cfa/ps/pressinfo/200PHAs.html

(2) LEONIDS: RAPID INFORMATION DISSEMINATION
    Marc Gyssens <gyssens@charlie.luc.ac.be>

(3) COMPACTION AS THE ORIGIN OF THE UNUSUAL CRATERS ON MATHILDE
    NATURE, 11 November 1999

(4) NEW SCALE FOR IMPROVED SPACE WEATHER PREDICTION
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(5) IMPACT DIAMONDS IN A FENNOSCANDIAN CRATER
    F. Langenhorst et al., UNIVERSITY OF BAYREUTH

(6) CLIMATE CATASTROPHES
    M. Budyko, STATE HYDROL. INSTITUTE, ST PETERSBURG

(7) DOES LIFE'S HANDEDNESS SPRING FROM WITHIN?
    Andrew Yee <ayee@nova.astro.utoronto.ca>


==========
(1) 200 POTENTIALLY HAZARDOUS ASTEROIDS

From <http://cfa-www.harvard.edu/cfa/ps/pressinfo/200PHAs.html>

PRESS INFORMATION SHEET: Produced at the Harvard-Smithsonian Center for
Astrophysics (CfA), Cambridge, Massachusetts, U.S.A.

Today saw the announcement of the discovery of the two-hundredth PHA,
or "potentially hazardous asteroid". This milestone was reached with
1999 VP11, found on Nov. 7 by LINEAR, the Massachusetts Institute of
Techology's Lincoln Laboratory Near-Earth Asteroid Research project. In
less than three years this project has yielded more than one-third of
all the PHAs, which are asteroids that can pass within 0.05
astronomical unit (5 million miles) of the earth and are intrinsically
brighter than absolute magnitude 22 (suggesting that they are more than
about 600 feet across).. The first PHA, known as Apollo, was discovered
in 1932, and all but 15 of the PHAs have been found during the past 20
years. Just half of the PHAs have been discovered since the middle of
1997, with the recent LINEAR contribution supplemented by the
University of Arizona's longstanding Spacewatch project, with 12
discoveries; the Near-Earth Asteroid Tracking program of the Jet
Propulsion Laboratory, with six discoveries; the University of
Arizona's Catalina Sky Survey, with five; and the Lowell Observatory
Near-Earth Object Program, with four. The Arizona amateur astronomer
Roy Tucker has discovered two PHAs.

Mere categorization as a PHA does not imply that an object will pose
any danger to the earth during the next tens of millennia and more, but
this is a convenient subset of the more inclusive collection of
Near-Earth Objects, most of which actually come nowhere near the earth.
More than 40-percent of the PHAs have been so extensively observed that
there is no way more than one or two of these could conceivably be a
threat a half-millennium, say, from now. For another 30 or 40 percent
the minimum distances between their orbits and that of the earth are
currently too large for there to be any real possibility of an impact
within the next half-millennium. Only a fraction warrant any serious
examination for a possible impact during the next half-century or so.
And that examination is now routinely occurring, thanks mainly to the
efforts of the group at the University of Pisa. The number of actual
cases found where there has been any conceivable danger during the next
half century is remarkably small--four objects altogether. Knowing of
these cases in a timely manner then allows special observational
efforts to be made, including the search for images of these bodies in
the old photographic archives. It should be no surprise that further
observations will eliminate these possible dangers--almost all of the
time... At least for the intrinsically brighter objects, which include
those half a mile across and larger, and thanks to the dedication of an
ever-increasing set of observers, professional and amateur, the process
is working just fine.

Brian G. Marsden
1999 November 11

E-mail: bmarsden@cfa.harvard.edu

=============
(2) LEONIDS: RAPID INFORMATION DISSEMINATION

From Marc Gyssens <gyssens@charlie.luc.ac.be>

I N T E R N A T I O N A L   M E T E O R   O R G A N I Z A T I O N

1999 Leonids: Rapid Information Dissemination
---------------------------------------------

Dear meteor observer,

From earlier communications, you have learned that the IMO is setting
up a communication network to obtain reliable information as soon as
possible after the event in the morning of November 18. We invite you
to contribute to this effort.

First of all, we want to point out you must DISTINGUISH between the
USUAL OBSERVATIONAL REPORTS, such as collected by the IMO's Visual
Commission, and which may be used for detailed, global analyses, and
the "EXPRESS REPORT" described below which serves as sole purpose the
compilation of a rough but reliable picture of the activity within
hours after the event.

The EXPRESS REPORT should have the following format:

Meteo R. Observer
Fireball City (45N 10E)

Time Interval (UT)    Lim. Magn.    Nr. of Leonids     Remarks (if any)
-----------------------------------------------------------------------
01:15-01:30           5.8           27                 None
01:30-01:45           5.9           56                 None
01:45-02:00           6.1           156                None
    .
    .
    .

To the extent possible, bin your observations for this "express report"
in time interval of 15 MINUTES.

(Again, the full report of your observations will be different from
this express report, as shorter intervals are required as well as
magnitude distributions and some additional data - see the earlier
posted article with visual observing hints - but the above data
suffice for the purpose indicated.)

If you wish to collaborate with the IMO in this respect, please send
your express report for the night of November 17/18 ONLY (or, of course,
for any unexpected activity you might happen to witness)
*** IMMEDIATELY AFTER THE OBSERVATION *** to the following email
addresses:

wgn@imo.net
gyssens@hcoss.uia.ac.be

The latter is a back-up address in case Web-site access to www.imo.net
would prove to slow down our computer too much. This back-up address
will be active only on November 17 and 18!

Thank you in advance for any collaboration we may receive!

Marc Gyssens
International Meteor Organization

=============
(3) COMPACTION AS THE ORIGIN OF THE UNUSUAL CRATERS ON MATHILDE

From NATURE, 11 November 1999
http://www.nature.com/server-java/Propub/nature/402155A0.abs_frameset

Compaction as the origin of the unusual craters on the asteroid
Mathilde

KEVIN R. HOUSEN, KEITH A. HOLSAPPLE & MICHAEL E. VOSS

The asteroid Mathilde has suffered at least five giant impacts.
Previous studies suggest that Mathilde's giant craters should be
surrounded by blankets of ejecta that are kilometres deep, yet the
craters show no evidence of filling by material excavated during later
nearby impacts. Computer simulations of impacts have been used to
suggest that the absence of ejecta arises because the impact energy is
deposited in a small volume, due to Mathilde's unusually high porosity,
which produces ejecta velocities so high that nearly all of the
material escapes Mathilde's gravitational field. Here we report
laboratory measurements of high-velocity impacts into porous material,
which support an alternative explanation: the crater is formed mainly
by compaction, not excavation. The small amount of ejecta lofted in our
experiments have velocities sufficiently low that nearly all of the
material is redeposited within the crater bowl. The crater itself
results from material being compressed, rather than ejected. This type
of cratering implies that highly porous asteroids are minor
contributors of meteorites, because essentially no material escapes
the asteroids. Nature Macmillan Publishers Ltd 1999 Registered No.
785998

=============
(4) NEW SCALE FOR IMPROVED SPACE WEATHER PREDICTION

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

NOAA
Contact: Barbara McGehan

NEW NOAA SPACE WEATHER SCALES MAKE SOLAR MAX EFFECTS MORE PREDICTABLE

As the sun revs up for Solar Max, a time of intense solar activity, we
can look forward to increasingly turbulent space weather. Today the
National Oceanic and Atmospheric Administration introduced the
first-ever scales designed to characterize the severity and impact of
upcoming solar storms on public safety and services.

"NOAA's new scales are the Richter scales of space weather. For the
first time, we can predict the impact of solar storms, and these storms
may be a real Y2K problem," said Dr. D. James Baker, under secretary
for oceans and atmosphere and NOAA administrator. "When Solar Maximum
occurs, the sun bursts at its seams with explosive power, and as it
churns there is potential for electrical power outages, radio problems,
and the disabling of satellites. This can disrupt communications,
including broadcast transmissions and pagers," Baker said.

As the period during the 11-year solar cycle when the sun is most
active, Solar Maximum brings an increase in the number and intensity of
solar storms and their effects. Space storms, radiation showers, aurora
borealis, and affects on power grids and Global Positioning System
navigation and other systems are all expected during the upcoming Solar
Max period, which is expected to last about three years.

Already there is an increase in solar activity as the world approaches
another Solar Maximum. As we get farther into Solar Cycle 23,
expectations are that the sun will continue to rev up. Each time there
is a solar event, NOAA's National Weather Service includes information
on the event in its transmission of weather data.

Working like the Richter scale for earthquakes, NOAA's new space
weather scales describe the intensity and frequency of three kinds of
solar events: geomagnetic storms, solar radiation storms and radio
blackouts. "The scales are a giant step forward in informing the public
about the severity of these events and their expected consequences,"
said Dr. Ernie Hildner, director of NOAA's Space Environment Center in
Boulder, Colorado. Hildner said that physical measurements on the
scales will help the scientific and operations communities consistently
identify the intensity of solar events. Solar storms can vary, with
some equivalent to a thunderstorm on Earth, while others may be more
severe, with intensity similar to a hurricane or tornado.

Satellite expert David Desrocher, a senior engineer at The Aerospace
Corporation in Colorado Springs, Colorado, said that, "NOAA's new space
weather scales will significantly aid the space industry in
anticipating events, understanding effects, and developing more robust
satellite designs and mitigation strategies." John Kappenman, a senior
engineer at Metatech in Duluth, Minn., explained that space storms can
impact the operational reliability of electrical transmission systems
world-wide. "The previous solar cycle demonstrated just how seriously
the power industry needs to consider the potential impacts of
geomagnetic storms," Kappenman said.

One of the strongest impacts occurred during the last solar cycle in
1989, when the entire Province of Quebec went dark because a
geomagnetic storm caused power lines to overload.

NOAA's Space Environment Center in Boulder is responsible for issuing
warnings, watches and forecasts of the space environment and potential
impacts on Earth. The Center continuously monitors the solar
environment with a complex array of ground-based observations and
satellites operated by NOAA and its national and international
partners.

For more information on the Space Environment Center, check out
    www.spaceweather.noaa.gov

For a comprehensive list of charts and graphics see the following page:
    http://www.sec.noaa.gov/info/Media/

=============
(5) IMPACT DIAMONDS IN A FENNOSCANDIAN CRATER

F. Langenhorst*), G.I. Shafranovsky, V.L. Masaitis, M. Koivisto:
Discovery of impact diamonds in a Fennoscandian crater and evidence for
their genesis by solid-state transformation . GEOLOGY, 1999, Vol.27,
No.8, pp.747-750

*) UNIVERSITY OF BAYREUTH,BAYER GEOINST,POB 101251,D-95440
   BAYREUTH,GERMANY

We report here the first discovery of impact diamonds on the
Fennoscandian shield, in the deeply eroded Lappajarvi impact structure,
Finland. The tabular morphology and microstructural twin bands provide
evidence for the solid-state transformation of graphite to form these
diamonds within <1 s. Strong corrosion and coating of surfaces with
amorphous carbon may result from the thermal interaction of the
diamonds with enclosing impact melt. Because of their unique
characteristics, impact diamonds can be easily distinguished from
kimberlitic diamonds, in general. Durable impact diamonds may thus
serve as indicators of ancient impact horizons that could mark
biological and climatic catastrophes in Earth's history. Copyright
1999, Institute for Scientific Information Inc.

===============
(6) CLIMATE CATASTROPHES

M. Budyko: Climate catastrophes. GLOBAL AND PLANETARY CHANGE, 1999,
Vol.20, No.4, pp.281-288

STATE HYDROL. INSTITUTE,23 2ND LINE,ST PETERSBURG 199053,RUSSIA

Climate catastrophes, which many times occurred in the geological past,
caused the extinction of large or small populations of animals and
plants. Changes in the terrestrial and marine biota caused by the
catastrophic climate changes undoubtedly resulted in considerable
fluctuations in global carbon cycle and atmospheric gas composition.
Primarily, carbon dioxide and other greenhouse gas contents were
affected. The study of these catastrophes allows a conclusion that
climate system is very sensitive to relatively small changes in
climate-forcing factors (transparency of the atmosphere, changes in
large glaciations, etc.). It is important to take this conclusion into
account while estimating the possible consequences of now occurring
anthropogenic warming caused by the increase in greenhouse gas
concentration in the atmosphere. (C) 1999 Elsevier Science B.V. All
rights reserved.

===========
(7) DOES LIFE'S HANDEDNESS SPRING FROM WITHIN?

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

[http://www.academicpress.com/inscight/11111999/graphb.htm]

Thursday, 11 November 1999, 5 pm PST

Does Life's Handedness Spring From Within?
By Robert F. Service

Although amino acids and other molecules essential to life come in two
mirror-image versions, like a right and a left hand, biology without
fail grabs one and shuns the other. This bias has puzzled researchers
for decades. But at the International Symposium on Cluster and
Nanostructure Interfaces in Richmond, Virginia, on 27 October,
scientists reported preliminary findings indicating that the source of
the bias might lie in the heart of molecules themselves -- in the
so-called weak force that operates within the nuclei of atoms.

For decades, researchers have searched for a phenomenon --
astronomical, electromagnetic, or nuclear -- that could have imprinted
this handedness, or chirality, on nature. One candidate, the weak
nuclear force, governs the radioactive decay of a neutron into a proton
and an electron, and the force has a handedness: The decay always
produces an electron with a left-handed spin. Because the weak nuclear
force is the only chiral fundamental force in nature, it was tempting
to link it to the handedness of biomolecules. But proof was lacking.

At least that's the way things stood before chemical physicist Robert
Compton of the University of Tennessee, Knoxville, and colleagues
turned their hands to sodium chlorate. This salt forms crystals made of
atoms arranged in either a clockwise or counterclockwise spiral.
Environmental factors, such as stirring, can influence the direction of
those spirals. Compton and his colleagues wondered if lefty electrons
produced by radioactive decay could produce the same effect.

They weren't disappointed. When the researchers bombarded a solution of
sodium chlorate with left-spinning electrons from radioactive
strontium, they wound up with an excess of right-handed crystals. And
when they hit the solution with positrons -- positively charged
counterparts to electrons, which have the opposite spin -- an excess of
left-handed crystals formed.

"It's a very, very interesting experiment," says Roger Hegstrom, a
chemist at Wake Forest University in Winston-Salem, North Carolina. It
doesn't prove that the weak nuclear force is responsible for biology's
handedness, he says, but it's an important step in that direction.

1999 The American Association for the Advancement of Science

[Extracted from INSCiGHT, Academic Press.]

----------------------------------------
THE CAMBRIDGE-CONFERENCE NETWORK (CCNet)
----------------------------------------
The CCNet is a scholarly electronic network. To subscribe/unsubscribe,
please contact the moderator Benny J Peiser <b.j.peiser@livjm.ac.uk>.
Information circulated on this network is for scholarly and
educational use only. The attached information may not be copied or
reproduced for any other purposes without prior permission of the
copyright holders. The fully indexed archive of the CCNet, from
February 1997 on, can be found at http://abob.libs.uga.edu/bobk/cccmenu.html


*

LETTERS TO THE MODERATOR - CCNet, 12 November 1999
--------------------------------------------------


(1) FLUFFY ASTEROIDS SHOULD BE EASIER TO SHOVE AROUND
    Roy Tucker <tucker@noao.edu>

(2) ONE OTHER DOWN SIDE OF THE TORINO SCALE
    Mark Kidger <mrk@ll.iac.es>

(3) DUST VEILS & THEIR CLIMATIC EFFECTS
    Doug J Keenan <DJ.Keenan@virgin.net>

(4) MORE DETAIL NEEDED ON COMETARY DUST LOADING
    Roy Tucker <tucker@noao.edu>

(5) CHICXULUB IMPACT & THE DECCAN TRAPS
    Oliver Morton <abq72@pop.dial.pipex.com>

(6) K-T BOUNDARY IMPACT-VOLCANIC CONNECTION?
    Andrew Glikson <andrew.glikson@anu.edu.au>

(7) ANOTHER SCI-FI FABLE
    Stephen Ashworth <sa@astronist.demon.co.uk>


==========
(1) FLUFFY ASTEROIDS SHOULD BE EASIER TO SHOVE AROUND

From Roy Tucker <tucker@noao.edu>

At 09:59 AM 11/11/99 -0500, it was written in CCNet:

     >Crushable Asteroids May Absorb Impacts
     >By Robert Irion

     >Asphaug notes that such objects, which he calls "flying Rice
     >Krispie treats," might swallow projectiles without breaking apart
     >or significantly changing their orbits. That's potentially bad
     >news, Asphaug and Housen agree, if one of those rubble piles
     >takes dead aim at Earth: The menacing asteroid might just shrug
     >off efforts to deflect it.


Dear Dr. Peiser,

I'm puzzled. The deflection of an asteroid or comet is a variety of
inelastic collision. The primary considerations are the force applied
to the body and the total mass of the body. Given a choice between
being threatened by an asteroid made of light, fluffy stuff or solid
platinum-group metals, I would conclude that, for similar sized bodies,
the styrofoam asteroid should be easier to shove around. If the
objective was to disrupt a body, I would still prefer the styrofoam.
Am I missing something?

Best regards,
  - Roy Tucker

=================
(2) ONE OTHER DOWN SIDE OF THE TORINO SCALE

From Mark Kidger <mrk@ll.iac.es>

Dear Benny:

I have followed the debate on the Torino Scale with some interest. Not
having a vested interest in the issue as I only do a little work on
NEOs, I feel that I can look at it a little as an outsider would.

My first impression was of an analogy to the Richter scale. If
something is up there 6, 7, 8 you pay attention, and quickly! Whoever
though reported a Richter 1 or 2 earthquake on the tv news?

One of the oddities of the Torino scale is precisely the fact that it
is extremely difficult for an event to get above 1. Now that may well
be a good thing. Assuming that the media will only start to take an
interest as that number creeps up, and that a 2 or a 3 will be a very
very rare event, we can be quite sure that there would almost certainly
be no media interest in a possible impact during the rest of my career.
We certainly avoid any more 1997 XF11 or 1999 AN10 events. That would
allow serious investigation of the object before the media start to
take an interest.

There is however a down side and it needs to be carefully balanced. The
first thing is that if objects only rarely even start to register on
the scale with a "1", there are two effects. One is a public perception
that the problem has suddenly "gone away": I don't hear about it any
longer, ergo it does not exist. The truth is that the problem still
exists, will not go away, and can only get more serious if a reduced
public profile of the issue leads to a serious reduction in funding for
NEO programs. The second is that the scientific interest to follow-up
interesting cases will sharply reduce. Scientists do have to justify
their funding, they do need public interest; if it does not exist they
will move on to a topic that does offer such scope. This could lead to
a serious reduction in follow-up of cases perceived to be "low risk".
If people thing that this is silly alarmism, remember that it was only
due to the efforts of a Japanese amateur that 1997 XF11 was not lost
almost immediately after discovery - for whatever reason there was no
immediate professional follow-up.

My doubt is thus with a scale that will almost always be used at the
"0" or "1" level meaning that there is no significant danger. Torino
has a wonderful system for categorising "the big one" but, for the
general public, whether an object receives a "5" or an "8" will
probably only influence the level of panic generated.

If I were to suggest a modification, it would be to expand the lower
end of the scale in a similar way to the Richter scale: 0-3 ... normal,
no real danger; 4-5 ... worth watching, but not too serious; 6 and up,
ever increasing serious danger. But do things in such a way that
objects that register 2-3 on the scale are relatively frequent (maybe 1
to 2 per year) and that a "4" may happen every few years, "5"s though
should be infrequent and larger numbers very rare indeed. However, we
would avoid a public perception that there is no problem simply because
the scale does not easily start to move.

Mark Kidger

=================
(3) DUST VEILS & THEIR CLIMATIC EFFECTS

From Doug J Keenan <DJ.Keenan@virgin.net>

Benny,

Yesterday's posting by Roy Tucker assumed that the climatic
after-effects of an eruption are largely determined by the mass loading
of the atmosphere. This is false. The climatic after-effects are
largely determined by the sulfur mass loading of the stratosphere. For
an elaboration, see item 34 at

http://climate.envsci.rutgers.edu/robock/robock_volpapers.html

Roy Tucker's calculated upper-bound of 10^16 g of cosmic dust is orders
of magnitude larger than the sulfur mass loading of the stratosphere by
Tambora in 1815--which induced severe climatic after-effects.  Hence the
calculation does not show that cosmic dust cannot affect climate.

To get an idea of how sensitive Earth's climate system can be to
changes in received solar radiation, consider that the total energy
fluctuations over the 11-year solar cycle are <0.1%, and yet these
fluctuations are believed to significantly impact global climate [e.g.
J. D. Haigh, Science, 1996].

Cheers,
Doug Keenan
http://freespace.virgin.net/doug.keenan

============
(4) MORE DETAIL NEEDED ON COMETARY DUST LOADING

From Roy Tucker <tucker@noao.edu>

Dear Dr. Keenan,

My letter to CCNet indicated more detail was necessary which has now
been provided. The primary climate modification mechanism proposed is
the introduction of sulphur into the atmosphere, not just the increased
opacity due to dust. C1 carbonaceous chondrites have an average sulphur
content of 5.9% which would suggest that my model event would introduce
about 6x10^14 grams of sulphur. Since the yearly average volcanic
production of sulphur is about 1.3x10^13 grams
(http://blueskies.sprl.umich.edu/geia/emits/volcano.html) the
environmental consequence would indeed be significant. The eruption of
Tambora produced about 6x10^13 grams of sulphur
(http://volcano.cs.und.nodak.edu/vwdocs/Gases/eruptions.html).

The figure of 7.4 cubic kilometers was intended as an extreme example
and assumes the entire cometary nucleus was disrupted and uniformly
dispersed into a lunar orbit-sized coma. You'll agree that this is an
implausible scenario. The questions then are what is a more reasonable
number for the dust density in the coma of a comet (my value of 2 x
10^13 grams/cubic cm was a typo, of course. That should be 10^-13) and
how often will the earth pass through a cometary coma? I must defer
these questions to someone more familiar with these numbers than I.

If indeed the passage of the earth through a cometary coma can produce
some environmental consequence, how does the magnitude and frequency of
such events compare to those due to volcanic activity?

Best regards,
     - Roy Tucker

=================
(5) CHICXULUB IMPACT & THE DECCAN TRAPS

From Oliver Morton <abq72@pop.dial.pipex.com>

Benny

There was recently some more discussion on CCNet of the Deccan traps as
an antipodal response to the Chicxulub impact, an idea I've always
found rather intriguing. At the recent Geological Society of America
meeting I had a chance to talk to David Kring of the University of
Arizona, part of the group that put together the Chicxulub story. He
told me that current geochronology clearly shows the Deccan event
predating the impact by, IIRC, two million years or so. Assuming this
is correct, I suppose the impact might have had some effect on the rate
of the flood volcanism, but it could hardly have been causal.

On another point, Olaf Stapledon had no call to predict world war I
when he wrote "Last and First Men", since he had already lived through
it, serving with distinction in the Friends' Ambulance Unit.

Best, oliver

============
(6) K-T BOUNDARY IMPACT-VOLCANIC CONNECTION?

From Andrew Glikson <andrew.glikson@anu.edu.au>

Dear Benny,

In response to Oliver Morton's letter, the suggestion of antipodal
Chicxulub-Deccan connection  (Rampino and Caldeira, 1992, Geophys. Res.
Lett. 19, p. 2011) appears to be inconsistent with the 120 degrees
radial distance between these features on plate tectonic reconstructions
(see Fig. 4 in Sutherland, 1996, AGSO Journal 16: p.572). This in
itself does not disprove a possible non-antipodal relation, depending on
models of seismic shock propagation (Boslough et al., 1996, GSA Special
Paper 307, p. 541). From Ar-Ar work by Basu et al. (1993, Science 261,
p. 902) and Venkatesan et al. (1993, EPSL 119, p. 181) the main Deccan
trap volcanism has been preceded by minor rift-confined alkaline
volcanics c. 68.5 Ma and a basaltic phase about 66 Ma, and lasted as
late as 63 Ma. While there is some dispute regarding the accuracy of
the Ar-Ar ages (Feraud and Courtillout, 1994, EPSL 122, p.259), it is
possible that (1) impact and volcanism were not genetically connected;
(2) impact enhanced rather than triggered volcanism; (3) there has been
more than one impact, by analogy to impact clusters in the late
Triassic, late Jurassic and late Eocene, and (4) the yet-unproven "Shiva
crater" (Negy et al., 1992, Tectonophysics 206, p.341) beneath the
Deccan basalts being a possible candidate?  Since the mega-impact record
is only partly known, and as new mega-craters are being progressively
discovered, including in this part of the world, the jury is still out
regarding genetic impact-volcanic relations.

Andrew Glikson
12.11.1999

Research School of Earth Science
Australian National University
Canberra  ACT 0200 Australia
andrew.glikson@anu.edu.au

============
(7) ANOTHER SCI-FI FABLE

From Stephen Ashworth <sa@astronist.demon.co.uk>

Dear Benny Peiser,

I am sceptical about this old sci-fi fable in which carbon-based
creatures (us) create their own successor -- whether saviour or nemesis
-- in the form of germanium-based computer technology (see item 3, by
Arthur C. Clarke, CCNet 8 Nov. 1999).

May I suggest two points for consideration: (1) that just as computers
become more powerful, at the same time it becomes easier for us to
interact with them (consider the trend: punched cards, keyboard, mouse,
speech recognition, and now experiments in thought-directed computing
under way), and (2) that digital germanium-based thought has turned out
to be just as fallible as analog carbon-based thought, only in
different ways. These ideas point, not to the replacement of humans
with computers, but rather to a continuation of the present trend
towards symbiosis.

Stephen Ashworth
Webmaster, Space Age Associates
Fellow of the British Interplanetary Society
11 November 1999

-----------------
CCNet-LETTERS is the discussion forum of the Cambridge-Conference
Network. Contributions to the on-going debate about near-Earth objects,
the cosmic environment of our planet and how to deal with it are
welcome. The fully indexed archive of the CCNet, from February 1997 on,
can be found at http://abob.libs.uga.edu/bobk/cccmenu.html



CCCMENU CCC for 1999

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

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