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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