PLEASE NOTE:


*

CCNet, 73/2000 - 29 June 2000
------------------------------


     "So it could be that life did not originate in the warm puddle
     imagined by Darwin, or in the deep-sea hydrothermal vents, but
     somewhere else entirely. The big problem with the off-Earth idea,
     however, is that it does not solve the riddle of the origin of
     life, it simply moves the problem to a different location."
       -- Henry Gee, 27 June 2000


     "Attempts to categorize comets and asteroids as distinctly
     separate entities have failed, and astronomers should now consider
     these objects as members of a highly diverse family: the small
     bodies of the Solar System."
        -- Don Yoemans, California Institute of Technology


     "The link between dinosaurs and asteroids works against us in some
     ways. Too many people - scientists amongst them - think we are
     worrying about catastrophes that happen on timescales of tens of
     millions of years. The ones which should worry us - the 1 km
     impacts - are much more frequent than that."
        -- Duncan Steel, University of Salford



(1) IT CAME OUT OF THE SKY
    The Guardian, 29 June 2000

(2) WHAT IS THE DIFFERENCE BETWEEN ASTEROIDS & COMETS?
    Science-Week <prismx@scienceweek.com>

(3) LIFE, BUT NOT AS WE KNOW IT
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(4) SPACE WEATHER - ANOTHER COSMIC HAZARD TO EARTH?
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(5) SPACE DUST IN A VACUUM
    Physical Review Focus, 27 June 2000

(6) U.S. PRESIDENT LIKELY TO GIVE LIMITED GREEN LIGHT FOR
    MISSILE DEFENSE
    Washington Post, 27 June 2000

(7) TECHNOLOGICAL EVOLUTION: WORLD'S MOST POWERFUL COMPUTER
    TO REPLACE NUCLEAR TESTING IN U.S.
    MSNBC, 28 June 2000

(8) ANGER AT FATIMA 'BETRAYAL'
    The Times, 29 June 2000

(9) IRISH TIMES, IMPACT MAGNITUDES & IMPACT RATES
    Duncan Steel <D.I.Steel@salford.ac.uk>

(10) WHAT RELEVANCE HAS VATICAN ANNOUNCEMENT FOR SCIENTISTS?
     James Whitehead <jwhitehe@unb.ca>

(11) AND FINALLY: SPEEDING METEORITE KILLS SIX -- AT ATHEISTS' PICNIC!
     Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>


================
(1) IT CAME OUT OF THE SKY

From The Guardian, 29 June 2000
http://www.guardianunlimited.co.uk/science/story/0,3605,337611,00.html

It came out of the sky

Duncan Steel on stones from space rescued from the snow which may hold 
clues to the secret of life

A natural explosion near the US-Canadian border in January released
energy close to that of the Hiroshima nuclear bomb. No one was hurt,
although it shook up hundreds of locals. The blast, high in the
atmosphere, was the result of the arrival of a 150-ton rock from space.

Meteorites continually cascade down upon Earth. This was a big one. But
its scientific importance stems from its composition. It is a member of
a rare type known as carbonaceous chondrites.

These get their name from the large amount of carbon they contain,
mostly in the form of organic chemicals. Hundreds of amino acids have
been identified in the handful of samples found. Mostly black, a
fragment held in the hand gives off a smell similar to sulphurous oil. 
Many researchers believe the basic building blocks of life were
delivered to the early earth by such rocks.

This rare group of meteorites is thought to represent the most
primitive material in the solar system: the first solid lumps to have
coalesced as the sun, then the planets, asteroids and comets formed
from a huge cloud of gas and dust about 4.56 billion years ago.

Many small samples have been found through recent searches in the
Antarctic. When they arrived is not known, leading to worries about the
extent of contamination. That's an especial problem if one is looking
for evidence of extraterrestrial life, and the contamination question
has been one of the major arguments in the furore over the Martian
meteorites.

Nasa announced in 1996 that a meteorite from Mars found in the
Antarctic possibly contained microfossils. That basic idea was not new.
Back in the 1960s claims were made that carbonaceous chondrites
contain microfossils. A few scientists still argue this is so.

From this perspective, any observed carbonaceous chondrite fall is
invaluable. There were several in the 19th century, such as the Orgueil
meteorite, which landed in France in 1864, then a hiatus. In 1969, two
more arrived on opposite sides of the world: at Allende in Mexico, and
Murchison in Victoria, Australia.

What happened in Canada? People living in the area where Alaska,
British Columbia and the Yukon Territory meet saw the morning sky
suddenly light up at 8:43 on January 18, a blue-green streak skimming
rapidly over their region. Eye-witnesses described it as 10 times
as bright as daylight.

Minutes later the shock wave produced by its destruction about 10 miles
up was felt far and wide. US defence surveillance satellites had picked
up the flash, the data indicating the energy released to be equivalent
to about five kilotons of TNT.

The incoming rock must have been five or six yards in size, and
travelling at around 10 miles per second as it plunged into the
atmosphere.

A week later Canadian outdoorsman Jim Brook was driving his truck home
across the frozen expanse of Tagish Lake, about 50 miles south of the
town of Whitehorse, when he noticed a multitude of strange black
stones. Brook had been keeping his eye open for possible meteorites
and, as he related later, he had "already been fooled several times by
wolf droppings". But there was no doubt that these were space rocks.

He gathered up a few in the dusk, and returned to collect more the next
morning. Researchers in Canada and at Nasa's Johnson Space Center in
Houston were alerted, and it soon became apparent that this was a major
carbonaceous chondrite fall; hundreds of fragments were spread over an
area 10 miles by two.

The first group of scientists arrived in February. A big snowfall on
January 27, just after Brook collected his samples, meant there was no
chance of finding any meteorites then. But there would be a narrow
window of opportunity starting in mid-April, with the spring thaw. From
then until mid-May there was a race against time to collect as many
fragments as possible, before the lake became too unstable even to walk
on. By the end of May, all the ice melted and drowned the remaining 
meteorites.

"This is the find of a lifetime," said Peter Brown of the University of
Western Ontario, one of the team that recovered the meteorites. "The
size of the initial object, the extreme rarity and organic richness of
the meteorites combined with the number we have uncovered make this a
truly unique event."

About 500 separate samples were spotted, but only 200 collected. The
discrepancy was due to the meteorites burying themselves in the ice.
Being dark, they absorb most of the sunlight striking them, and so melt
their way down.

This, though, is a positive boon from the perspective of avoiding
terrestrial contamination: the meteorites had sealed themselves into
impervious cocoons of ice, which could be sawn out and kept
refrigerated.

Another search team member was the University of Calgary's Alan
Hildebrand. A decade ago he was one of the scientists who recognised a
huge crater on the Yucatan Peninsula of Mexico as the scar from the
asteroid or comet impact that seems to have wiped out the dinosaurs 65
million years ago. Now he was working in the frigid conditions of the
Yukon. "One day, while I was picking pieces of meteorite out of porous
ice, I thought that the experience must be a bit like sampling on the
surface of a comet," he commented.

This opportunity represents an extraterrestrial sampling project done
at a tiny fraction of the cost of a major space mission. The
observations of the meteorite entry have enabled us to determine its
original orbit around the sun.

Detailed investigation of the Tagish Lake meteorite may tell us much
about the origin of the solar system, and perhaps of life itself.
Researchers at the Open University and the Natural History Museum, who
will soon receive samples for analysis, are already licking their lips
at the prospect.

• Duncan Steel researches asteroids and comets at the University of
  Salford.
 
========
(2) WHAT IS THE DIFFERENCE BETWEEN ASTEROIDS & COMETS?

From Science-Week <prismx@scienceweek.com>

ON SMALL BODIES OF THE SOLAR SYSTEM

Other than the moons of the various planets, the chief small bodies
of the solar system are comets and asteroids.

In general, a comet is a kilometer-size chunk of ice and associated
dust and debris. The *Oort cloud is an apparent spherical shell of
comets 10,000 to 100,000 *astronomical units (AU) from the Sun and
the proposed source of comets that orbit the Sun. The cloud is at the
extreme edge of the Sun's influence, halfway to the nearest star, and
it is believed that when the cloud is perturbed by passing stars,
comets may be sent into a solar orbit. The size and structure of the
Oort cloud have been deduced from statistical studies of the orbits
of comets; there is no direct evidence for the cloud's existence.
Approximately 900 comets are known.
    
Asteroids (also called "minor planets") are small rocky objects, most
of which orbit the Sun in a belt between the orbits of Mars and
Jupiter. A few asteroids follow orbits that bring them into the inner
Solar System, and several asteroids occasionally pass within a few
tens of millions of miles of Earth. Some asteroids are located in the
orbit of Jupiter, and some asteroids have been detected as far away
as the orbit of Saturn. There are approximately 7200 known asteroids,
and a million asteroids are believed resident in the Solar System.
The consensus view is that asteroids are composed of material that
failed to build a planet at a distance of 2.8 astronomical units
from the Sun, perhaps due to the influence of massive Jupiter just
outside the asteroid belt. Until recently, the shapes and surface
features of asteroids were a matter of conjecture; during the past
decade, however, significant direct observations of asteroids have
been relayed back to Earth from spacecraft.

Classical astronomers have categorized comets and asteroids as
distinctly different entities with different histories and
compositions, but recent evidence is blurring the conceptual boundary
between these two groups of small Solar System bodies, and there are
several newly discovered objects that are considered to be both
comets and asteroids on the basis of their characteristics.

Don Yeomans (California Institute of Technology, US) presents a
review of recent research on comets and asteroids, the author making
the following points:

1) Recent observations have revealed comets in asteroid-like orbits
and asteroids in comet-like orbits. Both comets and asteroids can
evolve from the Oort cloud into highly inclined, even *retrograde,
orbits about the Sun, so orbital behavior is no better than physical
behavior for distinguishing comets from asteroids. The author
suggests that attempts to categorize comets and asteroids as
distinctly separate entities have failed, and that astronomers should
now consider these objects as members of highly diverse family: the
small bodies of the Solar System.

2) If all comets were solid dirty balls of water ice, then their bulk
densities would be approximately 1 gram per cubic centimeter. But
some comets have apparent low-density structures that are made from
several bits held together by little more than their own
self-gravity. This conclusion arose after some comets were observed
to break up as a result of tidal forces from either the Sun or
Jupiter, and more than two dozen other comets have split apart for no
obvious reason at all. In addition, comets that have apparently
transformed from active to quiescent objects suggest that some
cometary bodies do become defunct and join the ranks of the
asteroids. Low-density extinct comets can probably explain a
significant fraction of the near-Earth asteroid population, "so we
cannot assume that all objects that threaten Earth will have the same
composition or structure."

3) Asteroids have been classified according to the light reflected
from their surfaces -- their optical spectra. Although no two spectra
are exactly alike, most asteroids fall into one of two groups, the
C-type (carbonaceous) and S-type (silicaceous). C-type asteroids have
low reflectance (albedo) and may contain mixtures of hydrated
silicates, carbon, and organic compounds. S-type asteroids have
higher albedos and can contain pyroxene (silicates containing
magnesium, iron, and calcium), olivine (magnesium and iron
silicates), and nickel-iron metal. The C-type asteroids are most
common in the outer part of the main asteroid belt, and the S-type
asteroids are mostly found in the inner asteroid belt.

4) Meteorites are asteroid collision fragments that have fallen to
Earth, and as such are thought to hold clues regarding the early
history of asteroids. Because most asteroid fragments are rocky, they
can survive the passage through the atmosphere of the Earth. In
contrast, debris from comet streams nearly always burns up in the
atmosphere, sometimes producing spectacular meteor showers in the
sky, but leaving little evidence on the surface of the Earth. The
most common meteorite is the ordinary chondrite, which is composed
mostly of rocky silicates, and so has not experienced the chemical
differentiation associated with melting. Such chondrites are thought
to be some of the most primitive rocks in the Solar System, although
their parent asteroid type is not clear. On 22 March 1998, and
ordinary chondrite was observed to fall to Earth by 7 boys in
Monahans, Texas (US), and within 48 hours the meteorite was under
examination at the Johnson Space Center in Houston, Texas. Laboratory
analysis of the Monahans meteorite detected salt crystals embedded
with water in the form of brine, and the salt crystals were dated to
the very beginning of the Solar System, approximately 4.6 billion
years ago. This suggests the presence of liquid water on the parent
asteroid of this meteorite, and unless this water derived from a
collision with a salt-bearing icy comet, the parent asteroid itself
must have had flowing water within its interior structure. Far from
being the dry rocky bodies they were once believed to be, it would
seem that some asteroids, along with comets, might be significant
sources of water.
-----------
Don Yeomans: Small bodies of the Solar System.
(Nature 20 Apr 00 404:829)
QY: Don Yeomans, California Institute of Technology 818-395-6811.
-----------

Text Notes:
*Oort cloud: The cloud is named after Jan Hendrik Oort (1900-1992).
Oort first proposed the existence of the cloud in 1950. In 1927, Oort
calculated the mass and size of the Galaxy, and the distance of the
Sun from its center, from the observed movements of the stars around
the center.
*astronomical units (AU): 1 AU = the mean distance from the Sun to
the Earth = approximately 93 million miles, and exactly 149,597,870
kilometers.
*retrograde: Opposite direction as planets. Prograde = same direction
as planets.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 30Jun00
For more information: http://scienceweek.com/swfr.htm
-------------------

Related Background:
FIRST DISCOVERY OF AN ASTEROID WATER INCLUSION

The term "meteor" refers to a piece of solid matter from space that
penetrates the Earth's atmosphere at a hypersonic speed of typically
10 to 20 kilometers per second, with atmospheric friction causing it
to become incandescent. Outside the Earth's atmosphere, it is known
as a "meteoroid"; any part that survives passage through the
atmosphere and reaches the surface of the Earth is called a
"meteorite". Most meteorites are thought to originate in the asteroid
belt between the orbits of Mars and Jupiter, although tracking of
entry paths indicates that before colliding with Earth meteorites
have highly elliptical counterclockwise orbits about the Sun (in the
same sense as the planets).

Meteorites are often named after the place on Earth where they are
found, and they divided roughly into 3 main classes according to
their composition. "Iron meteorites" consist of an alloy of iron and
nickel; "stony meteorites" consist of silicate minerals; and
"iron-stony meteorites" are a mixture of the two previous types. The
stony meteorites are further divided into "chondrites" and
"achondrites". Chondrites contain small spherules of high-temperature
silicates ("chondrules") and constitute more than 85 percent of
recovered meteorites. The achondrites range in composition from rocks
made up essentially of single minerals (e.g., olivine) to rocks
resembling *basaltic lava. Each category is further subdivided on the
basis of chemical composition. "Carbonaceous chondrites" have little
or no metal but abundant carbon, and display evidence of chemical
alteration by water; they have the highest proportion of volatile
elements and are the most oxidized. "Ordinary chondrites" (the most
common type) are intermediate in volatile element abundance and
oxidation state.

All main types of meteorite have been dated isotopically, with most
studies involving the dominant chondrite fraction. There are no
obvious age differences between the meteorites of the various groups,
and chondrites, achondrites, and iron meteorites consistently yield
ages of approximately 4.45 to 4.50 billion years, which places the
origin of these objects in the era of the formation of the Solar
System.

Over the past three decades, researchers have become increasingly
aware of the fundamental importance of water and aqueous alteration
on primitive Solar System bodies. Some carbonaceous and ordinary
chondrites, long proposed as primordial material relatively unchanged
since formation, have apparently been altered by interactions with
liquid water within the first 10 million years after formation of
their parent asteroids. But the location and timing of the aqueous
alteration, or the nature of the aqueous fluid itself, are not known.
Researchers have attempted to model this aqueous process through
analysis of hydrated minerals present in the meteorites, and through
computer simulations of the alteration process, but a major obstacle
to the understanding of aqueous alteration of meteorites has been
the absence of actual samples of aqueous fluids in meteorites.

M.E. Zolensky et al (7 authors at 3 installations, US) now report the
discovery and characterization of aqueous fluid inclusions in an
ordinary chondrite, the Monahans (1998) object. The Monohans (1998)
meteorite fell on 22 March 1998 in Monahans, Texas (US). The fall was
witnessed by 7 boys, and the first of two stones was recovered
immediately and carried to the Johnson Space Center, where it was
broken open in a filtered-air, clean-room facility less than 48 hours
after the fall. The authors suggest this effectively eliminated the
opportunity for aqueous or other contamination. The authors report
the presence within the Monahans (1998) meteorite of crystals of
halite (NaCl) and sylvite (KCl) containing aqueous fluid inclusions.
The fluids are dominantly sodium chloride-potassium chloride brines,
but they also contain divalent cations such as iron, magnesium, or
calcium. The authors suggest two possible origins for the brines are
a) indigenous fluids flowing within the asteroid, and b) exogenous
fluids delivered into the asteroid surface from a salt-containing
object such as a comet. The authors further suggest that "in either
case, the inclusions provide ground truth concerning the nature of
water in the early Solar System."
-----------
M.E. Zolensky et al: Asteroidal water within fluid inclusion-bearing
halite in an H5 chondrite, Monahans (1998). (Science 27 Aug 99
285:1377)
QY: Michael E. Zolensky, NASA Johnson Space Center, Houston, TX
77058 US.
-----------

Text Notes:
*basaltic lava: Basalt is a dark gray to black igneous rock of
volcanic origin that cools rapidly. "Igneous rocks" are rocks that
have congealed from a molten mass.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 1Oct99
For more information: http://scienceweek.com/swfr.htm

Copyright (c) 1997-2000 SCIENCE-WEEK/Spectrum Press Inc.
All Rights Reserved

==============
(3) LIFE, BUT NOT AS WE KNOW IT

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

[http://helix.nature.com/nsu/000629/000629-5.html]

Tuesday 27 June 2000

Life, but not as we know it
By HENRY GEE

Life on Earth rose early. Our planet formed around 4,500 million
years ago. By 3,800 million years ago, life had evolved. The evidence
comes from chemical traces in rocks of this age discovered in
Greenland. The interval of 700 million years between the two events
may seem leisurely, but this is an upper limit. Researchers are 
beginning to suspect that if life evolved on Earth, it is likely that
it evolved very much more quickly than this. Why?

First, the early Earth was not a quiet place. For the first few
hundred million years of its existence, our planet was pounded by
immense impacts that would have made the end -- Cretaceous impact, 65
million years ago (thought to have wiped out the dinosaurs) seem as
destructive as a gentle caress with a week-old lettuce leaf.

For example, during this period the Earth is thought to have been hit
by a body the size of Mars, gouging out material that became the
Moon. Such impacts would almost certainly have sterilized the planet,
making it very difficult to imagine life becoming established for a
few hundred million years after the Earth's formation.

Second, the rocks from Greenland that bear the earliest known traces
of life are among the earliest known rocks of any kind to have
survived to the present day. This means that if older rocks were
found, they too might contain traces of life. In other words, we have
no direct, geological evidence for there having been a period in
Earth's history in which life was completely absent.

Life as we know it

By 3,500 million years ago, life was well established. We know this
because in the 1980s J. William Schopf of the University of
California, Los Angeles, discovered fossilized microscopic organisms
in 3,500-million-year-old rocks from the Apex Chert of Western
Australia.

These organisms were so-called 'cyanobacteria' (or blue-green
'algae') that live in large communities and produce layered
sediment-clogged structures called 'stromatolites'. The earliest
marine reefs were made of stromatolites, and they remained features
of the marine realm until animals appeared that could graze on
these tempting mats of bacterial slime.

The Apex Chert fossils provide a window on a community of organisms
living in the early part of the Archean Eon (conventionally, between
4,000 and 2,500 [sic!] years ago). But whereas the Apex Cherts shed
light on early life near the surface of the sea, Birger Rasmussen's
recent announcement [1] of filamentous microfossils associated with a
hydrothermal vent system raises the possibility that life existed in
the ocean depths at around the same time. So it now seems that by the
early Archean life had already made its mark in a variety of
environments -- raising, again, the question of the speed of its
appearance and evolution.

Here is another puzzle. The Archean world was very different from
that of today -- the atmosphere, for example, contained very little
oxygen -- but the Apex Chert cyanobacteria were very similar to
cyanobacterial species living today, suggesting that cyanobacteria
evolve extremely slowly.

This raises another conundrum: if cyanobacteria have hardly changed
in 3,500 million years, how could they have evolved so rapidly in the
preceding 700 million? Although microscopic, cyanobacteria are made
of cells and have a biochemistry as sophisticated as any other form
of life. How could they have evolved from a simple brew of chemicals
in so short a time?

These questions are leading researchers interested in the origin of
life to take another look at a suggestion usually considered crackpot
-- that life evolved elsewhere in the Universe and arrived on Earth
from space. They are now beginning to test this idea experimentally.

Bugs in space

NASA researchers have flown bacterial cultures in spacecraft to test
their endurance to vacuum and hard radiation. Amazingly, some
bacteria capable of shielding themselves in resistant spores can
germinate after many months of exposure to deep space. That, and the
increasing evidence that bacteria can survive burial in rocks for a
long time -- perhaps millions of years -- suggests that organic
matter is tough, and could, in principle, be carried from planet to
planet.

The other strand of evidence lies in asteroids and comets. These can
contain appreciable quantities of complex organic molecules such as
amino acids. The primordial oceans ofEarth may have been filled with
water from cometary impacts. Could these impacts have brought the
ingredients for life with them, perhaps fully formed?

So it could be that life did not originate in the warm puddle
imagined by Darwin, or in the deep-sea hydrothermal vents, but
somewhere else entirely. The big problem with the off-Earth idea,
however, is that it does not solve the riddle of the origin of life,
it simply moves the problem to a different location.

[1] Rasmussen, B. Filamentous microfossils in a
3,235-million-year-old volcanogeneic massive sulphide deposit. Nature
405, 676-679 (2000).

Macmillan Magazines Ltd 2000 - NATURE NEWS SERVICE

==============
(4) SPACE WEATHER - ANOTHER COSMIC HAZARD TO EARTH?

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

Swiss Re

Contact:
Steve Dishart
Corporate Communications
Swiss Re, New York
212/317-5640

New Swiss Re Publication: Increased Solar Activity Raises Risk for
Sophisticated Technological Systems

ZURICH, Switzerland, June 27, 2000 -- Our increasingly technology-
dependent world is sensitive to solar activity and to changes in this
activity. A new Swiss Re publication reveals that space weather not
only affects the functioning of technical systems in space and on
Earth, but may also endanger human health and life.

Space weather is largely determined by atomic particles emitted from
the Sun and the stars. The effects of this phenomenon are many and
varied: they include electronic failures, immediate and long-term
hazards to astronauts and aircraft crews, changed electrostatic
charges in satellites, interruptions in telecommunications and
navigational systems, and power transmission failures and disruption
to rail traffic. Solar activity reaches a maximum in an eleven-year
cycle; we are on the threshold of the next maximum in solar activity --
and thus increased influence of solar weather on the Earth -- which
scientists have forecast for mid-2000.

The publication covers the effects of space weather on our technology-
dependent world with a focus on electronics, space flight and aviation,
telecommunication, electric power transmission, the gas and oil
industry and railway systems. Besides presenting the hazards and
potential damage, the authors also examine predictability, forecasting
possibilities and countermeasures.

"Space weather - hazard to the Earth?" also examines the relevance of
space weather for the insurance industry: Are insurance covers, which
are mainly limited to sudden and accidental damage, more heavily
exposed than before, or less -- given the new knowledge about space
weather and the possibilities for dealing with it? Should events now
be considered foreseeable because of the constant improvements which
are being made in space weather forecasting? This much is certain: loss
mitigation measures are rapidly gaining in importance, and the insurance
industry should pay increased attention to the duties of the insured in
this area. The new solar activity maximum expected for mid-2000 could
be used as an opportunity to raise risk awareness and encourage more
appropriate behaviour. This would work to the benefit of all parties
involved: the number of vulnerable systems has increased and networks
have expanded greatly since the last maximum eleven years ago, which
in turn has augmented the risk for both policyholders and the insurance
industry.

For further information on the subject, access Swiss Re's website at
www.swissre.com . The publication "Space weather - Hazard to the
Earth?" can be downloaded from the internet,
http://www.swissre.com/e/issues/spaceweather.html .

==============
(5) SPACE DUST IN A VACUUM

From Physical Review Focus, 27 June 2000
http://focus.aps.org/v5/st29.html

The solar system is a dusty place. Astrophysicists see dust on the
moon, on asteroids, and in the rings of planets. The particles can
become electrically charged, which leads to surprising phenomena,
such as the layer of levitated dust the astronauts saw on the Moon.
The Sun's ultraviolet (UV) photons should charge up dust grains by
knocking off electrons, but this theory has not been proven in the
lab. By dropping dust grains through an evacuated chamber under UV
illumination, a team has confirmed that dust is charged by the
photoelectric effect, as they report in the 26 June PRL. Their paper,
which relies mainly on ideas from freshman level physics, firms up
the theory behind the electrically driven motion of dust around
planets, moons, and even spacecraft.

NASA first saw the levitated Moon dust with unmanned spacecraft in
the 1960s, and astronauts later observed a glow from dust suspended
above the lunar horizon at sunset. "You wouldn't think dust moves
around, because there's no air," says Scott Robertson of the
University of Colorado at Boulder, and researchers have assumed that
the dust levitation comes from the photoelectric effect: UV photons
eject electrons from the surface of an isolated grain, giving it a
positive charge. At the same time, the photons constantly knock
electrons off the Moon's surface rocks and create a continuous upward
spray of electrons. So dust grains near the surface are hit by more
electrons than photons, and they become negatively charged. At about
a meter above the surface, where photoelectrons are less plentiful,
the positively charged dust grains float, repelled by the
positively-charged Moon.

That's the theory. To prove that dust can become positively or
negatively charged by these schemes, Robertson and his colleagues
designed a simple experiment. They allowed individual 100 m diameter
particles of zinc, copper, and graphite to drop about 30 cm through
an evacuated chamber, illuminated by UV light from a powerful arc
lamp. The dust dropping mechanism was a small holder with a vibrating
bottom plate containing a single hole. "It's very similar to a salt
shaker," says Robertson. The grains dropped into a Faraday cup, which
allows a direct measurement of their charge. In a second set of
experiments, the team added a zirconium plate behind but close to the
path of the dropping dust grains to simulate the effect of a nearby
surface (such as moon rocks) that emits many photoelectrons.

Without the plate, the isolated dust particles acquired approximately
the charges the researchers expected, based on their photoelectric
properties: All were positive, near 40,000 electron charges. With the
zirconium plate in place as a source of photoelectrons, the dust
became negatively charged by about the same amount.

Robert Merlino of the University of Iowa in Iowa City says he was
surprised that the electrons ejected from a nearby surface could
overwhelm the photons hitting a dust grain and give it a negative
charge. "I would not have expected that the photoelectrons from the
surface could have made that much of a difference," he says. "This is
the sort of thing that you learn by doing experiments." Robertson
adds that an understanding of dust charging is important for modeling
the small-scale environments of spacecraft (including exhaust "dust")
as well as the large-scale effects of the coalescence of dust in the
forming of a solar system.

2000, The American Physical Society. All rights reserved.

==============
(6) U.S. PRESIDENT LIKELY TO GIVE LIMITED GREEN LIGHT FOR MISSILE DEFENSE

From Washington Post, 27 June 2000
http://washingtonpost.com/wp-dyn/articles/A6110-2000Jun27.html

President Clinton is likely to give a "limited green light" for a
national missile defense system if a crucial flight test goes well next
week, according to The Washington Post. This middle course would
arguably not violate the Anti-Ballistic Missile Treaty and would leave
decisions on expanding the system to successive administrations.

FULL STORY at
http://washingtonpost.com/wp-dyn/articles/A6110-2000Jun27.html

=============
(7) TECHNOLOGICAL EVOLUTION: WORLD'S MOST POWERFUL COMPUTER TO REPLACE NUCLEAR TESTING IN U.S.

From MSNBC, 28 June 2000
http://msnbc.com/news/426657.asp?cp1=1

By Bob Sullivan

June 28 —  IBM Corp. will soon deliver what it calls the fastest
computer ever to the Department of Energy’s Lawrence Livermore
Laboratory. But the monstrous machine — really 512 computers, and 8,192
microprocessors linked together — still isn’t quite big enough for
the monstrous task Livemore staff really have in mind. It’s designed to
precisely simulate the explosion of nuclear weapons, so the U.S. no
longer has to perform occasional nuclear testing.

FULL STORY at: http://msnbc.com/news/426657.asp?cp1=1

=================
(8) ANGER AT FATIMA 'BETRAYAL'

From The Times, 29 June 2000

Madrid: A shadow has been cast over one of Europe's most famous
Catholic sanctuaries after its mystique was punctured by the Vatican's
controversial decision to reveal the last of its secret prophecies
(Giles Tremlett writes). Six million penitents visited Fatima in
Portugal last year, in part attracted by a secret prophecy that,
according to popular belief, predicted a nuclear war or some other
doomsday event.

The penitents, some of whom traditionally make the last part of the
journey on their knees, left behind nearly 4 million in donations of
gold and jewellery.

The revelation on Monday that there were no doomsday predictions has
provoked angry reactions from the Portuguese church over the decision
to keep the prophecy secret for half a century.

"Dismayed, cheated and betrayed, that is how many people feel," the O
Publico newspaper said yesterday as it summed up the reaction in
Portugal to the third prophecy.

A Vatican statement showed that the end of the world had never been
foreseen in Fatima. The prophecy, based on a vision seen by three
shepherd children in 1917, instead predicted the murder of a
white-robed priest believed to be a Pope.

Bishop Januario Torgal demanded: "If the Vatican knew that it was not
apocalyptic, why on Earth did it only make it public now?"

A friar, Mario de Oliveira, even claimed that Sister Lucia dos Santos,
who saw the vision but did not write about it until 1944, lived in a
"delirious world of infantile fantasies" and suffered "religious
hallucinations".

Copyright 2000, The Times Newspapers Ltd.

=============================
* LETTERS TO THE MODEARTOR *
=============================

(9) IRISH TIMES, IMPACT MAGNITUDES & IMPACT RATES

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

Dear Benny,

The report from The Irish Times (26 June 2000; CCNet 27 June) again
portrays the confusion between:

(a) Impacts causing continental/global effects and killing some
    large number (billions) of humans - plus lots of other animals 
    too; and
(b) Impacts causing extinction events (mass extinctions or otherwise).

The final paragraph you carried was:

"All of the 900 referred to in the study are a kilometre in diameter
or larger, a size that could spell extinction for 90 per cent or more
of the species that currently occupy the Earth. One kilometre in size
is thought to be a magic number, because it has been estimated that
these asteroids are capable of wreaking global devastation if they hit
the Earth."

What Bill Bottke said in that second sentence is correct, although
some would argue for 2 kilometres, perhaps (and I'm sure Bill
actually said "kilometer" 8-]).

The first sentence, I assume written by the journalist, is incorrect
and misleading. One km impactors do not produce mass extinction
events. They might extinguish a hundred species of beetle with
restricted range, or even kill the mountain gorillas if the rock hit
Rwanda, but one would expect only a small (insignificant?) number of
extinctions from such a tiny event - only 100,000 megatons!

I will leave people more knowledgeable than I to distinguish between
species/genera/families etc. in this context.

The difference between impact magnitudes here is important in terms
of public perception. The hazard posed to individuals is much higher
for 1 km impactors arriving every 100-300,000 years, killing >25% of
humankind, than it is for >10 km impactors arriving every 10^7-10^8
years and causing extinction events. The former class are not
evidenced in the palaeontological record: how could they be, when
they don't cause (many) species extinctions?

The link between dinosaurs and asteroids works against us in some
ways. Too many people - scientists amongst them - think we are
worrying about catastrophes that happen on timescales of tens of
millions of years. The ones which should worry us - the 1 km impacts
- are much more frequent than that.

Duncan Steel

=================
(10) WHAT RELEVANCE HAS VATICAN ANNOUNCEMENT FOR SCIENTISTS?

From James Whitehead < jwhitehe@unb.ca >

Dear Benny,

Re: the header and two first items (repeated below) - I question
whether this is the appropriate forum for the dissemination of such
stuff. What relevance has it to the topic of this group?

After raising this concern, I would like to congratulate you on this
wonderful service to the community. I can only imagine how long it
takes to assemble the messages, which is one reason why I question
wasting time to include material which is completely off-topic.

All the best,

James Whitehead


   "We saw an Angel with a flaming sword in his left hand; flashing,
     it gave out flames that looked as though they would set the world
     on fire".
        -- Third Fatima Prophecy, 26 June 2000


(1) VATICAN TRIES TO STEM APOCALYPTIC ANXIETY
    Associated Press, 26 June 2000

(2) 'AN ANGEL WITH A FLAMING SWORD': THIRD FATIMA SECRET INCLUDES
     COMETARY IMAGERY
     Vatican, 26 June 2000

-------------
MODERATOR'S NOTE:

Dear James,


There are a number of reasons why I think it is relevant for us to
monitor and understand apocalyptic beliefs that are very widespread
both among traditional believers and secular prophets of doom. After
all, end-time anxiety is often associated with images of cosmic
catastrophes and global disaster as portrayed in ancient documents and
sacred texts. In all liklihood, apocalyptic imageries were originally
inspired by cosmic impacts which were witnessed by people who
interpreted such traumatic events as divine intervention and heavenly
punishment. Ever since ancient times, apocalyptic movements have had -
and still have - an enormous influence on society. It would be very
unwise to underestimate the potential power such beliefs still hold,
particularly in times of crisis and even in technologically advanced
societies such as the U.S. or Europe. Let us not forget that nearly 3
billion people around the world are followers of apocalyptic religions.
It would be unwise to ignore these powerful movements. Instead of
ridiculing chilliastic religions, scientific endeavour should try to
enlighten their historical origins and understand their social dynamics
that are deeply rooted in humankind's long-held perception of our
uncertain place in space. What is more, the boundary between
traditional apocalypticism and the scientific understanding of the
impact hazard has become rather blurred in recent years. After all,
both parties openly anticipate cosmic disaster at some time in the
future. What really devides the apocalyptic disciple (be it in
religious or secular format) from the scientific interventionist is
that the former has practically given in to fatalism, whereas
the latter is hoping to avoid doomsday by means of scientific knowledge
and technological intervention.


==============
(11) AND FINALLY: SPEEDING METEORITE KILLS SIX -- AT ATHEISTS' PICNIC!

From Ron Baalke < BAALKE@kelvin.jpl.nasa.gov >:

Here's a humorous story from the Weekly World News. In case you
didn't know already, Weekly World News is a tabloid with a similar
reputation as the National Enquirer. 

Ron Baalke

http://www.weeklyworldnews.com/stories/1992.html

SPEEDING METEORITE KILLS SIX -- AT ATHEISTS' PICNIC!

COPENHAGEN, Denmark -- Six people were killed when a meteorite fell
from the sky and crashed down onto the table where they sat -- during
the annual picnic of the Danish Atheist Society!

The mind-boggling tragedy is being hailed by Christian groups as "an
act of God's vengeance" -- a warning to all who flaunt their defiance
of Him.

The Danish Atheist Society -- a 562-member group that espouses
non-belief in a higher power of any sort -- holds its picnic
every year on the last Sunday in April.

The six fatalities included society president Bjorn Daschiel and his
wife Anne.

"It happened so fast," said Lizbeth Ahm, who was seated with her
husband at another table. "There was nothing anyone could have done.

"One moment everyone was laughing, enjoying the day. The next moment,
this red-hot ball of rock came hurtling down from  the sky and
smashed into Bjorn's table.

"The impact knocked us off our benches onto the ground -- and we were
at least 30 yards away. "Bjorn and the others were buried under it..
It was just horrible."

The incident has left many members of the society baffled and
questioning their position on theology.

"I'm still not quite ready to embrace the idea of God at this point,"
said Jens Bebe, society treasurer.

"But I must say it has me truly wondering. Why would that terrible
thing strike at that particular place at that particular time?"

Noted Danish astronomer Dr. Leif Knudsen says he's not sure what size
the deadly meteorite was -- but regardless, it was much larger before
it fell to Earth. "Meteorites are originally meteors, large heavenly
bodies speeding through space," Dr. Knudsen said.

"When they enter our atmosphere, they begin to disintegrate. This one
had reached the exact size to do what it did: To kill all six people
at the table and no one else.

"I don't know what the odds are of  something like that happening,
but they must be astronomical."

----------------------------------------
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CCCMENU CCC for 2000

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