PLEASE NOTE:


*

CCNet 80/2001 - 19 June 2001
---------------------------

"Shooting out jets of energy or blobs of stuff the size of Earth at
nearly light-speed, exploding stars called supernovae may hold more
potential peril than anyone had ever imagined, according to a growing
suspicion among some researchers. While scientists have long tried
to link supernovae to mass extinctions on Earth, there is no solid evidence.
But recent observations of high-energy emissions in space have some
scientists suggesting that our planet may in fact get fried every now
and then."
--Robert Britt, Space.com, 19 June 2001


"It has been proposed that in the distant future our descendants may
cause the Earth to move further away from the Sun by engineering close
flybys of a 100-kilometre asteroid on an extremely eccentric orbit. The
obvious alternative technology is to erect a sunshield at the L1
Lagrange point. This could be based on near-future (less than 100 years
ahead?) space construction technologies using asteroidal material.
It would offer immediate results, with precise control (perhaps like
a venetian blind) and relatively small risk."
--Stephen Ashworth, Oxford, 18 June 2001


"Using the relation given by Melosh one finds that an impact speed
in excess of 20 km/sec is necessary to achieve any substantial ejection
from Mars. Although numerically-speaking large body impacts on Mars
are dominated by asteroids, it seems very likely that an impact by a
comet is a rather better bet for liberating martian rocks onto heliocentric
orbits from which they may make their way to the Earth."
--Duncan Steel, Salford University, 18 June 2001


(1) COSMIC CANNON: HOW AN EXPLODING STAR COULD FRY EARTH
    Space.com, 19 June 2001

(2) SWISS GEOLOGISTS FIND MARS METEORITE IN OMAN
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(3) USEFUL LEGACY OF NUCLEAR TREATY: GLOBAL EARPHONES
    The New York Times, 19 June 2001

(4) COMETS NOT ASTEROIDS
    Duncan Steel <D.I.Steel@salford.ac.uk>

(5) COSMIC SUNSHIELD: AN ALTERNATIVE TO MOVING EARTH
    Stephen Ashworth <sa@astronist.demon.co.uk>

===============
(1) COSMIC CANNON: HOW AN EXPLODING STAR COULD FRY EARTH

From Space.com, 19 June 2001
http://www.space.com/scienceastronomy/astronomy/gammaray_bursts_010522-1.html

By Robert Roy Britt
Senior Science Writer

Shooting out jets of energy or blobs of stuff the size of Earth at nearly
light-speed, exploding stars called supernovae may hold more potential peril
than anyone had ever imagined, according to a growing suspicion among some
researchers.

While scientists have long tried to link supernovae to mass extinctions on
Earth, there is no solid evidence. But recent observations of high-energy
emissions in space have some scientists suggesting that our planet may in
fact get fried every now and then.

For three decades, scientists have been puzzling over brief but intense
flashes of energy known as gamma ray bursts. These GRBs, as they are called,
pack more punch than any other cosmic event. Their source has been a
mystery, but so far they have been observed only coming from the far corners
of the cosmos.

But for the past three years, increasing evidence has linked GRBs to
supernovae, a far more common event. The latest thinking, though
controversial, goes like this:

A giant aged star casts off its outer shell in a last gasp that sends a
bubble of matter and energy racing outward. The rest of the star's matter
implodes.

Jets of material, or perhaps individual blobs of matter, are later hurled in
two opposite directions, at nearly the speed of light, along the axis of the
rotating stellar corpse. These expulsions pierce the supernova's original
expanding bubble, generating a flash of high-energy radiation known as gamma
rays.

If the jets or blobs happen to be pointed our way, we see the event. And if
one were to be generated nearby in our galaxy and were directed at Earth,
some scientists say the planet could be toast.

Fry a planet

How bad could it be? While no one can say for sure, one gamma ray expert has
generated a frightening scenario.

Stanford E. Woosley, an astrophysicist at the University of California,
Santa Cruz, said that even from the far side of our galaxy, a GRB would be
as bright as the Sun -- not in visible light, but in gamma rays. Luckily,
most gamma rays -- all but the highest energy versions -- do not penetrate
Earth's atmosphere. But the visible light does.

"Something this intense would create an optical flash by scattering
electrons in the upper atmosphere and creating something like a
super-aurora," Woosley said. It's an idea he's working on but has not yet
published.

"The flash of heat and light might flash-burn anything not in the shade," he
said. "Heating the atmosphere would cause big winds. The air would be much
hotter for weeks, as hot as an oven depending on the distance. This would
affect the other side of the Earth eventually."

Ocean life would be spared in Woosley's scenario.

But there is no consensus on whether gamma ray bursts are actually linked to
supernovae, and there's even less agreement over how dangerous they might
be.

Still, NASA scientists acknowledge the threat, describing it this way on a
GRB informational Web page:

"A gamma ray burst originating in our neck of the Milky Way, within a
thousand light-years or so, could lead to mass extinction on Earth. Gamma
rays interacting in the Earth's atmosphere would burn away the ozone layer,
allowing deadly ultraviolet radiation to penetrate through the atmosphere.
The influx of radiation would lead to widespread cancer and other diseases."

Cold War error

Nobody was looking for gamma ray bursts when they were discovered in 1967
after U.S. satellites were deployed to monitor possible violations of the
Nuclear Test Ban Treaty. At first, researchers thought they were seeing
something generated in our galaxy. But later evidence showed the sources to
be scattered throughout the universe, all well beyond our galaxy.

Until recent years, researchers suspected that GRBs were the result of two
massive objects, such as incredibly dense aged stars called neutron stars,
falling together.

But more and more, supernovae are also suspects. The first link came on
April 25, 1998 when GRB 980425 was spotted coming from the direction of a
known supernova, SN 1998bw.

Talk about a powerful combination.

"These dying stars (supernovae) emit about as much energy in their
seconds-long final fling as in their whole history. The GRBs are apparently
a thousand times or so brighter than that," said John G. Learned, a particle
astrophysicist at the University of Hawaii.

"We are starting to think that GRBs could be just another view -- one you do
not want to witness in our galaxy -- of supernovae," Learned said. "Perhaps
these GRBs are just jets coming from supernovae, and we call them GRBs when
the jet is pointed right at us.

Learned said these jets, or cannonballs as one idea suggests, traveling at a
terrific speed about 99.99999 percent of the speed of light, "may even
[have] been the source of the great extinctions of life on Earth every few
hundred million years." (Other scientists suspect asteroid impacts or
climate change as primary causes.)

Cosmic cannon

While most researchers imagine a supernova's expulsion as a jet of
high-speed energy, a more fantastical idea conjures an image of a giant
cosmic cannon lobbing Earth-sized globs of matter into space.

The idea was developed by Arnon Dar of the Israel Institute of Technology
and Alvaro De Rujula of CERN -- the European Organization for Nuclear
Research. The genesis of their idea was published in Physical Review Letters
in 1998 and was modified and updated last year.

It starts with the same supernova scenario -- the death of giant stars,
which were plentiful in the early universe. (In fact, when scientists see a
gamma ray burst, they are typically witnessing something that occurred
billions of years ago, and the light is just now arriving.)

A day or two after a supernova has sent its initial bubble racing into
space, Dar explains that some of the ejected material can fall back.
Ultimately, this generates a hyperdense neutron star or, in some cases, a
black hole. A swirling disk of material, called an accretion disk, develops
around this object.

In Dar's cannonball model, large amounts of matter sometimes slap against
the central object. The globs of matter are hurled outward at near
light-speed, racing in opposite directions along the object's axis of
rotation (just like the jets in the more common explanation).

These globs generate a GRB when they overtake the escaping supernova
material.

Dar said there is "a growing body of direct and indirect evidence" for the
scenario. He added that such an event would occur in our galaxy and be
pointed our way once every 100 million years. Dar noted that the five
greatest known mass extinctions on Earth are also separated by 100 million
years, on average.

And, Dar said, it could happen again.

The real threat from such events, Dar said, is not even the "normal" gamma
rays that researchers are only beginning to understand. Instead, higher
energy gamma rays and cosmic rays, thought to be created by the same events
but not currently measurable, are the true death rays of the cosmos.

When these bursts of energy interact with our atmosphere, Dar said they
would produce a lethal dose of byproducts -- particles called muons.

"Most of the species on Earth -- on the ground, underground and in the
oceans, seas and lakes down to tens of yards (meters) -- will be extinct
directly by these penetrating muons," Dar said.

Hypernova

Jerry Fishman, chief scientist for gamma ray astronomy at NASA's Marshall
Space Flight Center, said most supernovae do not generate these high-speed
emissions, jets or blobs and thus have no potential to generate a GRB.

Only a few, which he and other researchers have come to call hypernovae, are
capable. Their origins involve stars 50 to 100 times as massive as our Sun.

"These are very rare objects, but they were perhaps more numerous in
star-forming regions of the early (distant) universe," Fishman said. But, he
added, "there are likely to be several of the massive pre-hypernovae stars
in our galaxy. If any go off within several hundred parsecs (a parsec equals
about 326 light-years) and are beamed toward Earth, it would be very bad for
us."

One known supernova, suspected by some of being a hypernova, sits right in
our cosmic backyard. Eta Carinae is the most luminous object in our galaxy
and less than 8,000 light-years away. The exploding star is thought to be
100 times more massive than our Sun and it radiates about 5 million times
more power.

As seen from Earth, Eta Carinae brightened dramatically about 150 years ago,
then faded to become a dim star. But it has brightened again since about
1940 and it doubled in brightness between 1998 and 1999.

Dar said Eta Carinae does not seem to point in our direction.

An uncertain premise

Abraham Loeb, a professor of astronomy at Harvard University, is not
convinced there is any connection between GRBs and supernovae. He said there
is an important theoretical roadblock that researchers must still knock
down: "Instabilities on the surface of such a jet will tend to mix it with
the dense medium that it traverses and the feasibility of penetrating a full
envelope of a massive star was not demonstrated yet."

And while Loeb does not rule out the possibility that GRBs could harm life
on Earth, he noted that the danger is not likely an imminent one.

"I do not think GRBs pose a danger to life on Earth more substantial than
other astrophysical catastrophes such as normal supernovae, which are much
more frequent," he said.

Many theories have been put forth suggesting supernovae alone might be
dangerous, and experts say it might be true for those within about 30
light-years. Possible effects are similar to those outlined for GRBs --
brief doses of high-level radiation -- but are not widely agreed upon.

Eli Waxman, of the Weizmann Institute of Science in Israel, is even less
worried.

"Gamma rays would be absorbed high in the atmosphere, affecting the ozone
layer and producing some strange isotopes, but I think the energy is not
sufficient to cause extinction," Waxman said.

Answers hidden in even stranger concepts

Regardless of their dangers, GRBs and their enigmatic sources create a
captivating puzzle that researchers around the world would like to solve.

One way astronomers are gaining new insight into GRBs is by using the
orbiting Chandra X-ray Telescope to study an afterglow of the events that
generate GRBs. The Hubble Space Telescope can also observe an optical
afterglow.

But to really get under the hood of a GRB, some researchers are hoping to
observe and study some related particle ejections that exist so far only in
theory.

Learned, the University of Hawaii researcher, said that when the expanding
bubble of a supernova is pierced, the interaction ought to also generate "a
terrific hail" of super-high-energy neutrinos. These invisible particles are
thought to zoom through space at nearly the speed of light. While not
confirmed to exist yet, less energetic versions have been observed.

Several efforts to detect neutrinos are underway. One is a distribution of
sensors buried in Antarctic ice. Another employs the Moon as a detection
device.

Arnon Dar, co-creator of the cannonball model, won't be surprised if these
and other efforts eventually uncover an extreme cosmic irony.

"The solar system and the elements we and our planet Earth are made of were
created by a local supernova some 5 billion years ago," Dar said.
"Ironically, GRBs from other galactic supernovae may also be a main cause of
the major mass extinctions on our planet."

Copyright 2001, Space.com

===========
(2) SWISS GEOLOGISTS FIND MARS METEORITE IN OMAN

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

Joint University of Bern/Natural History Museum Bern news release

Contacts:

Dr. Beda Hofmann
Natural History Museum Bern
beda.hofmann@nmbe.unibe.ch, phone +41 31 350 72 40

Dr. Marc Hauser
Institute of Mineralogy and Petrology, University of Bern
hauser@mpi.unibe.ch, phone +41 31 631 87 95 or +41 79 252 83 79

Dr. Edwin Gnos
Institute of Mineralogy and Petrology, University of Bern
gnos@mpi.unibe.ch, phone +41 31 631

Prof. Dr. O. Eugster
Physikalisches Institut, Space Research & Planetary Sciences, University of
Bern

Embargo date: June 15, 2001 10:00 am central European time

Swiss geologists find Mars meteorite in the Sultanate of Oman

Exciting find of a Mars meteorite in Oman

Geologists from Bern University and from the Natural History Museum Bern
have found more than 180 meteorites in Oman in January/February 2001. The
most exciting find is a piece of Mars rock. This meteorite just received its
name: Sayh al Uhaymir 094. Contrary to other finds of Mars meteorites in
deserts, this meteorite is fully available to science. Detailed
investigations are currently under way at Bern University and at
collaborating institutions.

Just 18 meteorites from Mars are known today. Some have been fragmented
during their fall. Sayh al Uhaymir 094 is a fragment of the 16 th known Mars
meteorite. The geologic past of Mars, including the fate of water, as well
as the search for evidence of possible past life on Mars are research areas
in which Mars meteorites play a key role. Meteorites from the red planet
are of extreme scientific value because they are the only solid material
available for about 10 years to come. If all goes well, about 500 g of Mars
samples will then be returned to Earth at very high costs by spacecraft.

Sayh al Uhaymir 094: a window into Mars's past

SaU 094 is, besides the antarctic finds, the only Mars meteorite fully
available to science. Applying modern analytical tools at Bern University,
the mineralogical characterization was possible using tiny fragments. The
nature of the minerals as well as their chemical composition clearly
demonstrate that SaU 094 is a Mars meteorite. It is a piece of rock that was
formed from molten lava, similar to volcanic rocks on Earth. The origin from
Mars is supported by measurements of oxygen isotopes (Ian Franchi, Open
University, UK). Using X-ray tomography at EMPA, Dübendorf (Switzerland),
the interior of the rock was investigated nondestructively. An interesting
result of this investigation is the occurrence of many cavities up to
several millimetres in size, probably an effect of intense mechanical stress
during ejection from Mars. For detailed analyses samples will be cut from
this stone. The majority of these analyses (mineralogy, chemical
composition, noble gases, age determination etc) will be conducted at Bern
University. The availability of SaU 094 provides a new focal point for Swiss
Mars science.

Why are so many meteorites found in Oman? Meteorite falls are very rare.
Only where the surface of the Earth remains undisturbed and dry for very
long times meteorites accumulate over thousands of years. Enrichments of
this type were first detected in Antarctica and since about 10 years deserts
are being searched for meteorites systematically. From the Sahara about 2000
meteorites are known already. The Sultanate of Oman has become known as an
important collection area for meteorites just in the past two years. It is
spectacular that in this short time six Lunar and two Martian meteorites
have been found in Oman. All meteorite searches so far have been conducted
without permission from the Omani authorities. The meteorite Sayh al Uhaymir
094 was published in the Meteoritical Bulletin on may 23, 2001. The official
text from the Bulletin is given below:

THE METEORITICAL BULLETIN

Announcement 85-5, May 23, 2001
Jeffrey N. Grossman, Editor (jgrossman@usgs.gov)
Jutta Zipfel, Co-editor for Saharan Meteorites (zipfel@mpch-mainz.mpg.de)

Sayh al Uhaymir 094   20 deg 59.469 min N, 57 deg 20.326 min E Oman
Found 2001 February 8

Martian meteorite (shergottite)

A 223.3 g partially crusted stone was found in the same area as Sayh al
Uhaymir 005, 008, and 051 by Marc Hauser and Lorenz Moser (Bern) during a
search for meteorites. All samples may be paired. Mineralogy and
classification (E. Gnos, Institute for Geological Sciences, Bern) and B.
Hofmann (NMB): the grey-greenish rock shows a gabbro-like texture and
contains phenocrysts of olivine (average maximum dimension = 1.5 mm)
displaying shock-twinning, mosaicism, and, locally, oxidation; optically
clear parts of olivines (Fo65-69) occur in a fine-grained (average maximum
grain size = 0.3 mm) groundmass consisting of maskelynite (An55-64Or5-9) and
pigeonite (En60-68Wo7-9) with minor augite, chromite and pyrrhotite;
partially recrystallized veins and pockets of shock-melted glass containing
vescicles are abundant; x-ray tomography revealed that the specimen contains
approximately 0.4 vol% of pores up to 3 mm in size; shock stage, S5;
weathering grade, W1; small rusty pockets are Fe-hydroxide replacements of
an unknown pre-existing phase. Specimens: all in NMB.

Fascination Mars

The red planet exerts great fascination to humans since antiquity. What is
the justification, however, to investigate such a distant object in detail?
The history of planet Earth can only be understood in context with the
common origin with other planets and with the sun 4600 million years ago.

From all the planets Mars is most earthlike. There is evidence indicating
that both planets developped in a similar way for the first 1000 million
years, a time during which life established itself on Earth. The recent
recognition of extreme environments of life on Earth, e.g. in submarine
springs at 110 C and in porous rocks several kilometers below the surface
demonstrates that Early Mars most likely offered environments prone for
Life.

18 Meteorites are the only objects from planet Mars currently available.
Every piece provides new insight into the origin and development of our
neighbour planet. Additionally, meteorites represent potential "spaceships"
for microbes. Detailed studies of all processes affecting meteorites during
their journey yields answers to the question of whether interplanetary
transfer of microbes is a likely process.

How are Mars meteorites delivered to Earth?

Fragments of planet Mars are naturally delivered to Earth. Impacts of large
meteorites on Mars produce craters. Rocks close to craters may be ejected
with high velocity. To escape the gravity field of Mars, a velocity of at
least 5 km per second (approx. 20,000 km/h) is necessary. Ejected rock
fragments may approach Earth after millions of years, enter the atmosphere,
and end up as a piece of rock in the desert. Research on Mars meteorites
(e.g. at the Institute of Physics of Bern University) demonstrates that the
transfer between Mars and Earth took between 0.7 and 20 million years for
different meteorites.

Mars research: International efforts

Since the announcement of possible traces of life in the antarctic Mars
meteorite ALH84001 in 1996 Mars research has boomed. Even though the
arguments presented in 1996 are hardly taken as solid evidence today, this
and consecutive studies have initiated a new era of Mars research pushing,
among other things, the foundation of the NASA Astrobiology Institute (NAI).
In Europe the European Astrobiology Network was founded in May 2001.

New Mars meteorites were found in increasing rates in the last years, and
several missions to Mars (some successful, others not) were undertaken. One
mission (Mars Odyssey 2001) is currently on the way to Mars. Three missions
will attempt to reach Mars in December 2003 and January 2004,
among them ESA's Mars Express with the lander Beagle 2. NASA's Mars Global
Surveyor is orbiting Mars since 1997 and is providing a wealth of new data
about the Martian surface.

Mars research in Switzerland

Different scientific institutions are busy with Mars research also in
Switzerland. Mars meteorites are being studied since many years in the group
of Prof. O. Eugster at Bern University. Here noble gas contents are
measured, allowing a determination of the time the meteorite was exposed to
the space environment, and with that, the ejection age from Mars. At ETH
Zurich rare isotopes are being determined in Mars meteorites. For the Mars
lander Beagle 2 the Swiss electronics/microtechnics company CSEM in
Neuchâtel provides the cameras for panoramic, close-up and microscopic
imaging. In collaboration with CSEM test images of terrestrial materials are
being made at the Natural History Museum Bern. There will be a press
orientation about the involvement of CSEM in the Beagle 2 mission on June
15, 2001 at 16.00 in Neuchâtel (see link in website).

The science team

Bern University conducts intensive research in the Sultanate of Oman since
more than 30 years and has made a significant contribution to the
development of this modern state. Besides geological mapping and prospection
for raw materials, research was mainly focused on subjects like origin of
the Oman Mountains, palaeoclimate and ground water resources. Students from
Oman are integrated in ongoing projects and receive training at Bern
University. Many of these projects were supported by the Swiss National
Science Foundation. Thanks to these longstanding good relations with the
Sultanate of Oman, the first official meteorite search project could be
realized in January/February 2001.

[NOTE: Full text of this media release is available as a PDF file (856KB) at
     http://www.nmbe.ch/abtew/mars/marse.pdf

Images supporting this release are available at
     http://www.nmbe.ch/abtew/mars/marspress2.html

==============
(3) USEFUL LEGACY OF NUCLEAR TREATY: GLOBAL EARPHONES

From The New York Times, 19 June 2001
http://www.nytimes.com/2001/06/19/science/19NUKE.html

By WILLIAM J. BROAD

Though the Senate voted two years ago to reject a treaty that bans nuclear
testing, one of its provisions is alive and thriving: the global network of
sensors meant to listen for clandestine nuclear blasts.

Though still under construction, the International Monitoring System is
already yielding a wealth of science spinoffs, detecting violent winds,
volcanic eruptions and the crash of meteoroids from outer space.

"It's a vast new tool," said Hank Bass, director of the National Center for
Physical Acoustics, based at the University of Mississippi. "For the first
time, we'll have a global system of microphones listening to the atmosphere
of the planet."

The Comprehensive Test Ban Treaty calls for 90 countries to be host to a
network of 321 stations whose sensors monitor the land, sea and air for
faint vibrations and other telltale signs of nuclear blasts. More than 100
stations are now relaying data by satellite and cable to Vienna, where 220
people work at the system's headquarters.

Despite the Senate rebuff in 1999, the United States is a major backer of
the monitoring system. It pays about a quarter of the total costs, and
United States technical and scientific support is regarded as crucial to the
network's success.

Earlier this year, some treaty opponents tried to halt the financial aid,
saying the ban's goals were illusory or contrary to American interests. But
its backers fought back vigorously, led in part by Senator James M. Jeffords
of Vermont, whose defection from the Republican Party put Democrats in
control of the Senate earlier this month. Battles over the monitoring system
continue in Washington, and it is unclear if American support will continue.

Experts on both sides say the existence of an effective monitoring system,
which its proponents see as central to treaty policing, would increase the
chances that the accord might one day be revived.

In all, the surveillance system is to have 170 stations that detect
underground shock waves, 11 that track undersea explosions, 80 that sniff
the air for telltale radioactivity and 60 that listen for revealing sounds
in the atmosphere, including winds and shock waves.

Dr. Gerardo Suarez, a geophysicist from Mexico who directs the International
Monitoring System in Vienna, said the emerging network was starting to
excite experts far beyond the world of arms control. "The scientific
community is awakening to the enormous possibilities," he said in an
interview.

Interested groups, he said, include the World Meteorological Organization,
which wants wind data for global weather forecasting, and the World Health
Organization, which wants to track radioactivity in the atmosphere.

"It's a tremendous challenge," Dr. Suarez said of building the global
network. "There's never been anything like it. We have stations from the
Arctic to Antarctica."

New additions to the surveillance system include ground-based microphones
that listen to the air for low- frequency sounds far below the range of
human hearing. Dr. Douglas Christy, head of the acoustic group in Vienna,
said that by the end of the year some 20 of the 60 sound stations will be
operational.

"Things are moving along very rapidly," he said. "It's hectic. But we're
happy with it."

On April 23, the fledgling system detected a speeding meteoroid that crashed
into the atmosphere over the Pacific, where it produced a blast nearly as
powerful as the atomic bomb dropped on Hiroshima.

In the past, such explosions often escaped notice because they usually occur
over the sea or uninhabited lands. The new information will help scientists
calculate how often these strikes occur and the odds of "doomsday rocks"
hitting the planet.

Today, the International Monitoring System and its member states are keeping
the data private among themselves until global agreements can be made for
its wider release, Dr. Suarez said. A few nations, he said, fear that
improper analysis of the data might confuse small explosions in the mining
or construction industries with clandestine nuclear blasts.

Preliminary work on the monitoring system began in late 1996 after the
treaty was opened for signature and has been accelerating ever since. In the
United States, the Defense Department does much of the work.

Treaty opponents have argued that small blasts can elude the monitoring
system and that America might one day need to test its old nuclear arms or
design new ones.

When the Senate in 1999 rejected the treaty, conservative Republicans tried,
but failed, to cut the monitoring funds as well.

Early this year, just after President Bush took office, they launched a new
drive. On March 12, Senator Jesse Helms, the North Carolina Republican who
then was chairman of the Foreign Relations Committee, wrote the State
Department to urge that the United States remove its signature from the
test-ban treaty and "terminate funding" for its organizations, including the
network of sensors.

On April 4, 10 Senate Republicans, including Mr. Helms and Trent Lott of
Mississippi, then majority leader, made the same argument to Donald H.
Rumsfeld, the defense secretary. "We urge you," they wrote, "to terminate
Defense Department efforts to implement the treaty."

Treaty opponents call support for the system - or any provision or
organization called for in the treaty - a surrogate for backing the treaty
itself, which is why they want the monitoring effort halted.

Frank J. Gaffney Jr., a former Pentagon official who opposes the pact, said
in an interview that the monitoring is "a backdoor way to get us" into the
treaty. Mr. Gaffney, who directs the Center for Security Policy, a private
group in Washington, said establishing the monitoring system "creates a
rubric in which a future administration might endorse the treaty."

Senator Jeffords, a longtime treaty supporter, fought back on April 6,
urging Secretary of State Colin L. Powell to persevere. "We must avoid any
weakening of our commitment to international nuclear test monitoring," he
wrote in a letter with Senator Lincoln Chafee, a moderate Republican from
Rhode Island.

A few weeks later, on May 10, Secretary Powell told Congress that the Bush
administration would seek $20 million for the test-ban work next year. That
figure is what the program office in Vienna had requested.

Secretary Powell is one of the few officials in the Bush administration to
have supported the Senate's approval of the treaty, which he did in January
1998 along with three other former chairmen of the Joint Chiefs of Staff.

Mr. Jeffords, in announcing his departure from Republican ranks on May 24,
made no mention of the test ban or its monitoring. But aides said the topic
was one of many where he foresaw growing disagreements with the Bush
administration and Senate leaders.

Daryl Kimball, executive director of the Coalition to Reduce Nuclear
Dangers, a private group in Washington, said the Senate's shift into
Democratic hands will aid the monitoring and "make life far more difficult
for the Dr. Strangelove caucus."

If the United States and the 159 other nations of the treaty organization
maintain their contributions, construction of the monitoring system could be
completed by late 2005, Dr. Suarez said. That is somewhat behind the
schedule envisioned a few years ago.

By late this year, he said, his team will have finished surveying 90 percent
of the proposed station sites around the world, many of which lie in remote
or inhospitable regions.

In the United States, despite the political clash over monitoring, 26 of 37
planned stations have already been built, a Bush administration official
said.

The White House might want to pull out of the monitoring program after it
finishes its reviews of nuclear policy, the official added. But the
president and his aides, though largely treaty opponents, will probably
choose to avoid that step and the likely uproar.

"The politics are really hairy," the official said. "They may want to let it
limp along because of its high political profile."

Copyright 2001, The New York Times

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

(4) COMETS NOT ASTEROIDS

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

Dear Benny,

In his nice essay concerning transpermia, Michael Paine begins by talking
about "the ejection of surface rocks from Mars during impacts by large
asteroids".

The feasability of target (planetary) material being thrown off Mars depends
critically upon the impact speed. Using a sample of over 600 observed
Mars-crossing asteroids I calculated a mean impact speed of 9.3 km/sec, with
less than five percent of the impacts at greater than 20 km/sec and rather
less than one percent occurring at greater than 30 km/sec. On the other
hand, with an assumed spherical distribution of near-parabolic comets with a
uniform distribution in perihelion distance (i.e., coming from the classical
Oort-Opik cloud) I find a mean impact speed of 45 km/sec, a mode of 55-56
km/sec, and a maximum impact speed just below 60 km/sec, with a very small
fraction having any impact speed *below* 30 km/sec. (Reference: Duncan
Steel, "Distributions and moments of asteroid and comet impact speeds upon
the Earth and Mars", Planetary and Space Science, volume 46, pp.473-478,
1998.)

Using the relation given by Melosh (H.J. Melosh, "The rocky road to
panspermia", Nature, volume 332, pp.687-688, 1988) one finds that an impact
speed in excess of 20 km/sec is necessary to achieve any substantial
ejection from Mars.

Although numerically-speaking large body impacts on Mars are dominated by
asteroids, it seems very likely that an impact by a comet is a rather better
bet for liberating martian rocks onto heliocentric orbits from which they
may make their way to the Earth. If I recall correctly, the known Mars
meteorites show groupings in space exposure ages that would indicate a small
number of impacts having ejected these objects within the last 10-100
million years or so. This would be consistent with the very occasional
high-speed comet impacts being responsible, rather than the greater number
of lower-speed asteroid impacts.

Duncan Steel

=============
(5) COSMIC SUNSHIELD: AN ALTERNATIVE TO MOVING EARTH

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

Dear Dr Peiser,

It has been proposed that in the distant future our descendants may cause
the Earth to move further away from the Sun by engineering close flybys of a
100-kilometre asteroid on an extremely eccentric orbit (Don Korycansky, Greg
Laughlin and Fred Adams in Astrophysics and Space Science, see CCNet 79/2001
- 18 June 2001, items 7, 8 and 9).

The obvious alternative technology is to erect a sunshield at the L1
Lagrange point. This could be based on near-future (less than 100 years
ahead?) space construction technologies using asteroidal material. It would
offer immediate results, with precise control (perhaps like a venetian
blind) and relatively small risk.

Surely it is strange that The New York Times and The Observer reported the
planet-moving proposal without even mentioning whether or not the authors
compared the pros and cons of their plan against such an obvious
alternative?

Yours sincerely,

Stephen Ashworth
Oxford, UK
Fellow of the British Interplanetary Society
Webmaster, Space Age Associates
18 June 2001

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