CCNet DIGEST, 7 December 1998

    Ron Baalke <>

    Michael Paine <>

    The Sunday Times, 6 December 1998


    K.O. Pope et al.,



From Ron Baalke <>

Marshall Space Flight Center

On December 13, 1998, fragments of a curious object called 3200
Phaethon will produce a beautiful sky show

Dec. 4, 1998: 1998 was a great year for meteor watching. In November
the much-anticipated Leonids produced an outburst of nearly 600
meteors per hour, punctuated by a spectacular display of fireballs
seen worldwide. The October Giacobinids were also a pleasant surprise
for many, thanks to an outburst over Japan and east Asia. As 1998
winds down, there is one more opportunity to view a dazzling sky
show: the annual Geminids meteor shower.

The shower officially begins on December 6th, but it doesn't peak
until the night of the 13th. Unlike the Giacobinids and Leonids, the
Geminid's broad maximum lasts nearly a full day, so observers around
the globe have a good chance to see the show. At its peak the
Geminids are expected to produce about one shooting star every 30

Most well known meteor showers, like the Perseids and Leonids, are
old. They've been observed for hundreds or even thousands of years.
The earliest record of a modern-day meteor shower is probably a
notation in Chinese annals dated 36 AD, regarding the Perseids, where
it is said that "more than 100 meteors flew thither in the morning."

The Geminids are a different story. The first Geminid meteors
suddenly appeared in the mid-1800's. Those early showers were
unimpressive, boasting a mere 10-20 shooting stars per hour. Since
then, however, the Geminids have grown in intensity until today it is
one of the most spectacular annual showers. In 1996, the last time
the Geminids appeared in a dark moon-less sky, observers saw as many
as 110 per hour. Sky-watchers with clear skies should see at least
that many this year if the Geminids continue to intensify.

After the discovery of the Geminids in 1862 astronomers began
searching for the parent comet. Most meteor showers result from
debris that that boils off a comet's nucleus when it passes close to
the sun. This debris orbits the sun along with the comet, forming a
thin, elongated stream of meteoroids that become shooting stars when
they hit Earth's atmosphere.

Years of searching proved to no avail until finally, in 1982, NASA's
Infrared Astronomical Satellite discovered a curious object moving in
the same orbit as the Geminid meteoroid stream. The orbital match was
so good that it had to be the source of the debris, but to the
surprise of many it wasn't a comet. The source of the Geminids was
apparently a rocky asteroid.

3200 Phaethon, as the asteroid is now known, is in a highly
elliptical 1.4 year orbit that brings it within 0.2 AU (astronomical
units) of the Sun. It made its closest recent approach to Earth in
December 1997 when it passed within 0.31 AU of our planet.

But how does an asteroid produce a meteoroid debris stream? Comets do
it easily whenever they pass close enough to the sun to heat their
frozen nucleus. Tiny bits of ice and dust naturally bubble away into
interplanetary space. Rocky asteroids are made of tougher stuff,
however, so it is unclear how bits of 3200 Phaethon would break or
boil off to form a meteoroid stream.

One of the earliest ideas was that Phaethon might occasionally
collide with other asteroids. Collisions would create a stream of
pulverized rocks that would account for the Geminids meteor shower.
Phaethon's orbit passes through the asteroid belt just beyond Mars,
so at first this hypothesis seemed likely, but more detailed studies
disagree. The orbits of individual Geminid meteoroids are not
consistent with the idea that they broke free while in the asteroid
belt. Instead, they appear to have crumbled away when Phaethon was
closer to the Sun. In this respect Phaethon is behaving like a

So, is Phaethon a comet or an asteroid?

There are arguments in favor of both. Phaethon's spectra look like
those of a rocky asteroid, but its orbit is similar to that of a
comet. When Phaethon passes by the sun it doesn't develop a cometary
tail, but bits and pieces do break off to form the Geminid
meteoroids. By studying photographic records of fireballs, scientists
have estimated the density of the Geminid meteoroids to be between 1
and 2 gm/cc. That's less dense than typical asteroid material (3
gm/cc), but several times denser than cometary dust flakes (0.3
gm/cc). Many astronomers now believe that Phaethon is an extinct or
dormant comet that has accumulated a thick crust of interplanetary
dust grains. Phaethon's thick mantle gives it the outward appearance
of an asteroid, but underneath lies the nucleus of a comet.

The origin of the Geminids may not be fully understood until future
space travelers pay a visit to the asteroid-comet 3200 Phaethon.
Until then we can still enjoy the sky show and savor the mystery of
the enigmatic Geminids.

How to View the Geminids

Geminids meteors can be seen anytime after 10 p.m. local time, when
the constellation Gemini is well above the horizon, but the best time
to look is during the early morning hours between about 2 a.m. and
dawn. That's when the local sky is pointing directly into the Geminid
meteor stream.

Gemini rises about 08:00 p.m. local time at mid-latitudes in the
Northern hemisphere. The radiant of the Geminid shower is located
near Castor, one of the two bright stars in Gemini (the other bright
star is Pollux). To find the constellation at 2:00 a.m., go outside
and face south. Castor and Pollux will appear approximately 45
degrees above the horizon. Earlier in the evening, from 10:00 p.m.
until midnight, Gemini will be about 30 degrees above the horizon in
the southeast.

You won't need binoculars or a telescope, the naked eye is usually
best for seeing meteors which often streak more than 45 degrees
across the sky. The field of view of most binoculars and telescopes
is simply too narrow for good meteor observations.

Experienced meteor observers suggest the following viewing strategy:
Dress warmly as the mid-December nights are likely to be cold in the
Northern hemisphere. Bring a reclining chair, or spread a thick
blanket over a flat spot of ground. Lie down and look up somewhat
toward the south. Meteors can appear in any part of the sky, although
their trails will tend to point back toward the radiant.


From Michael Paine <>

Dear Benny,

I have prepared a draft web page which is intended to replace the
"Tsunami from asteroid impacts" web page. Based on the assumptions set
out in the revised page, the risk to low-lying coastal areas is
substantially less than my original estimates (which, it turns out, were
based on worst case scenarios) but still significantly greater than
"inland" locations.

The URL is
Comments are most welcome.

Michael Paine
New South Wales Coordinator, The Planetary Society Australian Volunteers


From The Sunday Times, 6 December 1998

by Matthew Campbell, Washington

IN AN intrusion on the domain of Hollywood villains bent on world
domination, China is said to have embarked on a quest for a giant
blowtorch-like weapon that can fire a laser beam hundreds of miles into
space to destroy satellites as they orbit the earth.

A secret Pentagon report warning of what some call the "death ray" has
alarmed the American military, whose own tests have revealed the
vulnerability of military satellites to being "fried" in a laser
attack. Intense research is being conducted to develop ways of
protecting vital intelligence-gathering and communications satellites
from attack.

Amid fears of a new arms race in space, America is also experimenting
with a laser weapon capable of destroying Scud missiles in flight. The
research would warm the heart of Ronald Reagan, the former president
whose dreams of using lasers in space to defend America from incoming
nuclear missiles were widely dismissed as an expensive folly.

America has already test-fired a laser at one of its own obsolete
satellites, ostensibly to gather information about its satellite
fleet's susceptibility to enemy attack. Amid secrecy reminiscent of the
early days of nuclear weapons, it is designing even more elaborate
anti-satellite weapons, including a spacecraft that "captures"
satellites and drags them down into the atmosphere, where they burn up.

Even while they profess to be trying to avoid the militarisation of
space, other countries such as Russia are pursuing anti-satellite
weapons programmes. International treaties may prohibit the placing of
weapons of mass destruction in space but there are no bans on firing
lasers into the heavens.

The Pentagon report said the Chinese - as part of a plan to modernise
their military forces and consolidate their position as the dominant
power in Asia - were developing anti-satellite technology. They were
being aided, it said, by scientists from the former Soviet Union whose
own anti-satellite weapons programme has been hampered by economic
chaos in Russia and lack of funds.

The report revealed that China was also developing so-called "radio
frequency" weapons as part of an "electronic warfare" arsenal designed
to inflict havoc on an enemy by interfering with communications. In the
field of laser technology, the report said that China "may already
possess the capability to damage, under specific conditions, optical
sensors on satellites".

The aim, said the report, was to "develop a capability to establish
control of space or to deny access and use of military and commercial
space systems in times of crisis or war". Congress was briefed about
the threat. "It is real and substantive," said Curt Weldon, a
Republican congressman.

America fears anti-satellite weapons could be used by its enemies to
deprive it of its key advantage in any future conflict by disabling its
"spies in the sky". Hundreds of military satellites orbiting the earth
provide America and its allies with tactical information about
potential enemies. They also play a crucial role in military targeting,
communications and navigation.

According to western intelligence sources, the Chinese were
particularly impressed by the advantage satellites gave American
forces in the Gulf war in 1991 by pinpointing Iraqi troops and
equipment. Chinese military planners have expressed anxiety that this
edge might be used against them in any Asian conflict.

It is believed the Chinese have developed their laser weapon along the
lines of America's so-called MIRACL laser, which has been tested at the
White Sands missile range in New Mexico.

The army spent more than $1 billion developing the laser, which is
housed in a complex the size of a small factory. It burns chemicals and
uses mirrors to focus a one megawatt stream of energy into a 6ft-wide
beam that acts like a giant blowtorch and can disable satellites
hundreds of miles away within seconds.

After the apparatus was test-fired at an old military satellite in
1997, the Pentagon was extremely coy about divulging any details about
the results. However, military sources said the satellite had been
badly damaged.

Other techniques for disabling satellites, remnants of Reagan's beloved
Strategic Defence Initiative - otherwise known as Star Wars - are
quietly moving off the drawing board into the hardware stage as
American military thinking increasingly envisages space as a future

"We look at space as the pipeline of the 21st century, similar to oil
in the 20th century," said Brigadier-General Alan Johnson, director of
plans at US Space Command, explaining the military's growing interest
in space.

American military forces depend more on satellites for communications
and observation than those of any other country. Boris Yeltsin, the
Russian president, has called for a moratorium on the testing of
anti-satellite weapons. But it is unlikely to be heeded - least of
all by the Chinese as they seek to modernise their armed forces.

In America, laser technology is being promoted not just for use
against satellites: the air force is developing an airborne laser
system carried by a jumbo jet for finding and destroying Scud
missiles within seconds of their launch. Travelling at 186,000 miles
per second, a laser beam could reach out across thousands of miles to
knock out a missile in the time it takes to travel a few feet.

Eventually lasers might be placed in satellites that could find and
destroy missiles armed with nuclear, chemical or biological weapons.
While some critics balk at the idea of letting laser weapons into
space, the threat posed by rogue dictators such as Iraq's Saddam
Hussein suggests that the "death ray" may be the deterrent of the

Copyright 1998, The Sunday Times


D.H. Erwin: The end and the beginning: recoveries from mass
extinctions. TRENDS IN ECOLOGY & EVOLUTION, 1998, Vol.13, No.9,

121, WASHINGTON, DC, 20560

The evolutionary consequences of mass extinctions depend as  much on
the processes of survival and recovery following these biotic crises
as on the patterns of extinction themselves. Paleontologists are
currently documenting biotic recoveries from six major mass
extinctions and several smaller biotic crises. Although the immediate
responses are remarkably similar after each event, with low-diversity
assemblages dominated by widespread, eurytopic species, the recovery
response in the long-term is more varied. Lineages that survive the
extinction can lack the resilience for recovery, whereas others
vanish from the fossil record seemingly to return from the dead after
several million years. Copyright 1998, Institute for Scientific
Information Inc.


K.O. Pope*), S.L. D'Hondt, C.R. Marshall: Meteorite impact and the mass
extinction of species at the Cretaceous/Tertiary boundary. PROCEEDINGS
1998, Vol.95, No.19, pp.11028-11029



J.C. Ahouse: The tragedy of a priori selectionism: Dennett and Gould on
adaptationism. BIOLOGY & PHILOSOPHY, 1998, Vol.13, No.3, pp.359-391


In his recent book on Darwinism, Daniel Dennett has offered up a
species of a priori selectionism that he calls algorithmic. He used
this view to challenge a number of positions advocated by Stephen J.
Gould. I examine his algorithmic conception, review his unqualified
enthusiasm for the a priori selectionist position, challenge Dennett's
main metaphors (cranes vs. skyhooks and a design space), examine ways
in which his position has lead him to misunderstand or misrepresent
Gould (spandrels, exaptation, punctuated equilibrium, contingency and
disparity), and discuss recent results in developmental biology that
suggest that an a priori position does not fill the demands of an
evolutionary biology. I conclude by insisting that evolutionary biology
is many leveled, complicated, and is carried on an ever shifting and
expanding empirical base that when disregarded results in caricature.
Copyright 1998, Institute for Scientific Information Inc.

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