PLEASE NOTE:
*
CCNet 109/2001 - 19 October 2001
================================
"What was first thought to be a meteorite that flashed
across
the southern Alberta sky could be an asteroid about twice the
size of an elephant, says a geological expert. "This object
was
probably an asteroidal fragment entering the atmosphere,
something in
the region of one to 10 tonnes," said Alan Hildebrandt,
co-ordinator of the Canadian Fireball Reporting Centre, which is
a
volunteer arm of the Canadian Space Agency." "The
loudest sounds
reported so far seem to be from the Banff area, so that
presumably means
the terminal burst, the explosions at the end where the object
fragmented, were relatively near there." "Much of the
object
disintegrated into dust, but some of the strongest pieces would
survive," he said.
--Calgary Sun, 16 October 2001
"It appears that the Yarkovsky effect causes a hurry-up of
the
orbital evolution, and so can explain the brief space exposure
ages of meteorites. There is another important implication of
this
work. In making predictions of the tracks of asteroids and so
possible
impacts on the Earth, we generally assume that only gravity
affects
their motion. In such a complicated situation, even a tiny
additional perturbation like the Yarkovsky effect may make the
difference between a near-miss and a bull's-eye, the target being
this
little sphere in space we call our home."
--Duncan Steel, The Guardian 18 October 2001
(1) ASTEROID WITNESSES SOUGHT
Calgary Sun, 17 October 2001
(2) EXPERTS SEARCH FOR ASTEROID
Calgary Sun, 16 October 2001
(3) POLICE CALLED FOLLOWING ASTEROID CRASH
Vancouver Sun, 15 October 2001
(4) METEOR LIGHTS UP NIGHT SKY IN AUSTRALIA
Ron Baalke <baalke@jpl.nasa.gov>
(5) HALLEY'S COMET RETURNS ... IN BITS AND PIECES
NASA Science News <snglist@snglist.msfc.nasa.gov>
(6) SPACE DRIFTERS
Andrew Yee <ayee@nova.astro.utoronto.ca>
(7) HUNGARIAN HAS DINOSAUR 'WOBBLE' THEORY
The Budapest Sun, 18 October 2001
(8) FLOODS SWEPT ANCIENT NILE CITIES AWAY, EXPERT SAYS
National Geographic News, 17 October 2001
(9) ANTARCTIC SEAFLOOR CORE SUGGESTS EARTH'S ORBITAL OSCILLATIONS
MAY BE
THE KEY TO WHAT CONTROLLED ICE AGES
Andrew Yee <ayee@nova.astro.utoronto.ca>
(10) PANIC COULD BE BIGGEST ILLNESS: PSYCHOLOGICAL DAMAGE AMONG
PEOPLE
COULD BE WIDESPREAD
The Guardian, 19 October 2001
(11) GIANT IMPACT -- HISTORY OR HOLLYWOOD?
Tom Van Flandern <tomvf@metaresearch.org>
(12) EDINBURGH'S GREAT CONTRIBUTION TO SPACE PROMOTION
Andy Nimmo <andy-nimmo@ntlworld.com>
(13) CORRECTIONS/WEB DIRECTIONS/SUGGESTION
Andy Smith <astrosafe@yahoo.com>
================
(1) ASTEROID WITNESSES SOUGHT
>From Calgary Sun, 17 October 2001
http://www.canoe.ca/CNEWSSpace0110/17_witness-sun.html
By PETER SMITH-- Calgary Sun
CALGARY -- Scientists tracking the spectacular asteroid seen by
numerous
people in Western Canada want to hear from witnesses who saw it
west and
north of Calgary.
"We'd really appreciate hearing reports from anyone in the
Rocky
Mountain House, Sylvan Lake, Sundre area who saw it on
Sunday," said
Alan Dyer of the Calgary Science Centre.
>From calls scientists have received, they believe they've
tracked the
asteroid's path for part of its journey through the atmosphere.
"It passed from B.C. into Alberta, somewhere north of Lake
Louise ...
heading in a northeast direction into Alberta," said Dyer.
"How far it
got is yet to be determined."
Scientists say it may have been up to 10 tonnes. They hope some
pieces
reached Earth and that more sightings will help find them.
Copyright 2001, Calgary Sun
============
(2) EXPERTS SEARCH FOR ASTEROID
>From Calgary Sun, 16 October 2001
http://www.canoe.ca/CNEWSSpace0110/16_asteroid-sun.html
CALGARY -- What was first thought to be a meteorite that flashed
across
the southern Alberta sky could be an asteroid about twice the
size of an
elephant, says a geological expert.
"This object was probably an asteroidal fragment entering
the
atmosphere, something in the region of one to 10 tonnes,"
said Alan
Hildebrandt, co-ordinator of the Canadian Fireball Reporting
Centre,
which is a volunteer arm of the Canadian Space Agency.
Hildebrandt is trying to collect information from as many
witnesses as
possible to pinpoint where the asteroid's remnants may have
landed after
it flashed across the afternoon sky Sunday.
So far, he's received sightings from Medicine Hat in the eastern
part of
Alberta to Mission in the lower mainland of British Columbia.
"It was seen over hundreds of kilometres of area even though
the region
was partially cloudy," said Hildebrandt.
"The loudest sounds reported so far seem to be from the
Banff area, so
that presumably means the terminal burst, the explosions at the
end
where the object fragmented, were relatively near there."
But Hildebrandt says if they fell in the Rocky Mountains, it's
unlikely
they'll be found. He is hoping the pieces may have landed in
fields
where farmers may find them.
"Much of the object disintegrated into dust, but some of the
strongest
pieces would survive," he said.
Randy Ilcisin was about 15 kilometres west of Sundre in
south-central
Alberta when he heard the asteroid exploding at 2:30 p.m.
"I heard what sounded like rumbling thunder, but the sky was
clear,"
said Ilcisin.
"We had no idea what it was. We thought it might be a
distant
landslide."
Copyright 2001, CNews, 2001
============
(3) POLICE CALLED FOLLOWING ASTEROID CRASH
>From Vancouver Sun, 15 October 2001
http://www.canada.com/vancouver/news/story.asp?id={6FDEBC95-E239-462B-BC45-43C650D17A7E}
Patricia Bailey
Vancouver Sun
Monday, October 15, 2001
A woman who told police she witnessed an airplane crash into a
hillside
near Mission probably saw an asteroid, says one of the province's
top
astrophysicists.
"I think it was probably a fireball," said Jeremy
Tatum, a University of
Victoria astronomer and B.C.'s official representative on the
Canadian
Space Agency's meteorites and impacts advisory committee (MIAC).
Mission RCMP say an unidentified woman called their detachment
Sunday
afternoon and said she saw an object that "glinted silver in
the sun,"
hit the side of a hill north of Deroche. The woman saw no smoke
or fire
in the spot where she thought the plane landed, said police.
"It's almost universal for a witness to think it's very
close. But
typically it's more than sixty kilometres up in the air,"
said Tatum.
Shortly after the woman contacted the detachment, police from
Mission,
Calgary, Cranbrook, Golden, Banff and Jasper received calls that
a
meteor was observed falling to the earth.
"A plane wouldn't have been seen over that wide an
area," said the
astrophysicist, who added that if the asteroid didn't break up in
the
sky first, it probably crashed to the earth in Alberta.
Asteroids, the source of many meteorites, are rocks, or small
planets
that orbit the Sun and range from a few kilometres to hundreds of
kilometres across. They are scattered through the solar system,
but most
are between Jupiter and Mars.
Tatum has asked a colleague in Alberta, Allan Hildebrand, who is
the
chair of MIAC, to help him investigate the sightings.
"If there are any reports from the West Coast, I would very
much like to
know," said Tatum, who has asked that people contact the
following
e-mail address with any information:
universe@uvvm.uvic.ca
© Copyright 2001 Vancouver Sun
==============
(4) METEOR LIGHTS UP NIGHT SKY IN AUSTRALIA
>From Ron Baalke <baalke@jpl.nasa.gov>
http://www.thewest.com.au/20011017/news/latest/tw-news-latest-home-sto28280.html
Meteor lights up night sky
The West Australian
October 17, 2001
POLICE received a number of reports of a bright flash or
explosion in
the skies last night when a meteor vapourised about 100km
north-east of
Perth.
Perth Observatory astronomer Peter Birch said the two-second
flash was
caused by a rock the size of a cricket ball burning up as it
entered the
atmosphere about 10.15pm.
Full story here:
http://www.thewest.com.au/20011017/news/latest/tw-news-latest-home-sto28280.html
=============
(5) HALLEY'S COMET RETURNS ... IN BITS AND PIECES
>From NASA Science News <snglist@snglist.msfc.nasa.gov>
NASA Science News for October 17, 2001
The annual Orionid meteor shower peaks this weekend on October
21st. Sky
watchers will see as many as 20 fast shooting stars each hour --
each
one a tiny piece of Halley's Comet. NASA scientists plan to
observe the
Orionids as a test of equipment they will use to record next
month's
much-anticipated Leonid meteor storm.
FULL STORY at
http://science.nasa.gov/headlines/y2001/ast17oct_1.htm?list20392
============
(6) SPACE DRIFTERS
>From Andrew Yee <ayee@nova.astro.utoronto.ca>
[ http://www.guardian.co.uk/Print/0,3858,4279294,00.html
]
Thursday, October 18, 2001
Space drifters
A peculiar pseudo-force has changed the way astronomers think
meteorites
reach Earth, explains Duncan Steel.
The Guardian
Meteorites are mostly chips off bigger blocks. Out in the main
belt,
between Mars and Jupiter, there are billions of asteroids.
Inevitably
there are collisions between them, and some of the debris
eventually
reaches us.
A simple picture, but there is a puzzle in the details. Most
meteorites
appear to be too young, in terms of the time spent on independent
orbits
after escaping their parent asteroids. Subject to the assumption
that
the gravitational tugs of the planets are the only forces at
play,
astro-mathematicians are able to trace how the paths of
interplanetary
objects wander. Such calculations lead to an estimate that
meteorites
need about a hundred million years to reach us, much longer than
they
actually take.
This transit time is known from a meteorite's space exposure age.
This
duration is quite different from the period it may have lain on
the
ground before discovery (between seconds and millennia), or its
age from
formation as measured using radioactive dating.
Space exposure ages are determined using cosmic rays. Within a
much
larger asteroid, an eventual meteorite is shielded by an
overlying layer
of rock. After an inter-asteroid collision, the freed meteoroid
is
suddenly exposed to the high-energy elementary particles that
permeate
space.
When these cosmic rays hit the meteoroid, they penetrate a
centimetre or
so. Characteristic tracks are left in the rock, which may be
studied
under a microscope. By counting the numbers of tracks it is
possible to
determine how long it took for the meteorite to travel from its
parent
asteroid to the Earth's surface. Typical values are a few million
years.
This implies that meteoroid orbits must evolve much faster than
purely
gravity-based computations would indicate. Something else must be
going
on. What could it be?
Consider the famous experiment of two cannonballs of different
size
being dropped from the Leaning Tower of Pisa. Both reach the
ground at
the same time, despite their differing masses: only gravity
matters
here.
This is not the case if a feather is substituted, because its
large
cross-section compared to its mass means that air resistance is
substantial. In a vacuum the feather falls at the same rate as
the iron
balls. Now think again about meteoroids in space. Are there any
influences that are size-dependent, causing them to evolve
dynamically
at a rate faster than pure gravity would allow? There is no air,
but is
there some other sort of resisting medium affecting their orbits,
helping them migrate inwards on a crash course with Earth?
The solar wind, the stream of charged particles moving outwards
from the
sun, imposes a small force. A greater pressure derives from the
photons
of sunlight. These two factors are important for tiny
interplanetary
dust grains, but a meteoroid the size of a basketball is
essentially
unaffected.
The sunlight absorbed by meteoroids can have other effects. They
are
heated by this flux, and that energy is then re-emitted as
infrared
radiation. The emission is not isotropic, though: it is not the
same in
all directions. This leads to two types of pseudo-force affecting
orbiting objects.
The first was discovered in 1903 by a British physicist, John
Poynting,
who spent his career at the University of Birmingham. Howard
Robertson
of the California Institute of Technology further explored this
concept
in 1937: in astronomical jargon it is known as the
Poynting-Robertson
effect.
Poynting reasoned that because the meteoroid is moving in its
orbit with
a speed of more than 10 miles per second, there are differing
Doppler
shifts on the infrared photons emitted in opposing directions.
Forward-emitted radiation is shifted to a shorter wavelength,
while
radiation emanating in the reverse direction is pulled out to a
longer
wavelength. As a result, more momentum is emitted forwards than
backwards, and there is a retarding force on the meteoroid
causing it to
spiral slowly in toward the sun. Although this is important for
objects
less than a few centimetres in size, it is not significant for
larger
bodies.
The second pseudo-force has only recently been recognised to be
of
consequence. The idea is not new: it was simply forgotten over
the
several decades since two Russian astronomers, named Yarkovsky
and
Radzievskii, explored how a warm object's spin may affect its
path.
The easiest way to comprehend the so-called Yarkovsky force is to
think
about the Earth rotating on its axis. Split its surface into four
time
zones. On the dayside are the morning and afternoon zones, on the
nightside there are pre- and post-midnight segments. Because it
takes
some hours for the temperature to rise during the morning, on
average
the afternoon zone is hottest, and so a greater share of the
radiation
emitted into space emanates from there. Diametrically opposed to
that
segment is the post-midnight zone, which is the coolest, and so
the
least radiation escapes from that region.
This non-isotropic emission of radiation provides a slight shove
in the
direction away from the afternoon segment, accelerating the
planet
slightly. In the case of a huge body like the Earth, there is no
measurable effect. But for a small spinning meteoroid, the
influence is
substantial.
It appears that the Yarkovsky effect causes a hurry-up of the
orbital
evolution, and so can explain the brief space exposure ages of
meteorites.
There is another important implication of this work. In making
predictions of the tracks of asteroids and so possible impacts on
the
Earth, we generally assume that only gravity affects their
motion. In
such a complicated situation, even a tiny additional perturbation
like
the Yarkovsky effect may make the difference between a near-miss
and a
bull's-eye, the target being this little sphere in space we call
our
home.
[Duncan Steel works at the University of Salford. His most recent
book
is Target Earth (Time Life).]
© Guardian Newspapers Limited 2001
===========
(7) HUNGARIAN HAS DINOSAUR 'WOBBLE' THEORY
>From The Budapest Sun, 18 October 2001
http://www.budapestsun.com/full_story.asp?ArticleId={091314B8A5D84603AE56BC9C59F26343}&From=News
By Gerson Perry
The extinction of the dinosaurs 65 million years ago may have
been
caused by a kind of astronomical "wobble" in Earth's
and Mercury's solar
orbits, according to a new theory being put forward by a group of
California scientists including a Hungarian.
Scientists have long speculated that a giant celestial body
slammed into
ancient Earth, near what is now Mexico's Yucatan Peninsula,
causing
dinosaurs to starve to death after the effects killed-off food
sources.
It is unclear whether the object that hit the Earth was a comet
or an
asteroid, but 20-year researcher Ferenc Varadi, who hails from
Hungary,
said that if he had to guess, he would choose the asteroid
theory.
Using computer models, University of California at Los Angeles
professors Bruce Runnegar, Michael Ghil and Varadi tracked
planetary
orbits as far back as 250 million years ago.
Varadi, 42, told reporters, "The original intent was to
obtain better
data on the orbits of the planets to better understand past
changes in
the Earth's climate."
The team's model showed that during the Cretaceous period,
gravitational
pushes and pulls with the Sun and other planets created a wobble
in the
Earth's orbit.
That wobble, in turn, may have caused Mercury's orbit to wobble.
Gravitational effects of the two celestial wobbles might have
forced a
large asteroid to break away from the asteroid belt and smash
into
Earth.
There are thought to be hundreds of thousands of asteroids in our
system, ranging in size from the very small to as large as a
mountain.
Most are floating in the main asteroid belt, an elliptical plane
between
Mars and Jupiter.
Varadi admitted the scientists' conclusions were largely the
result of
assumptions, but added, "This will probably result in a new
direction of
research."
He said the discovery would likely attract the interest of other
scientists who would work towards confirming the theory.
Copyright 2001, Budapest Sun
============
(8) FLOODS SWEPT ANCIENT NILE CITIES AWAY, EXPERT SAYS
>From National Geographic News, 17 October 2001
http://news.nationalgeographic.com/news/2001/10/1017_NileCities.html
By Hillary Mayell
Two cities that lay at the edge of the Mediterranean more than
1,200
years ago, Herakleion and Eastern Canopus, disappeared suddenly,
swallowed by the sea. Now, an international team of scientists
may have
figured out the mystery of why it happened.
The researchers have concluded that the two cities collapsed when
the
land they were built on suddenly liquefied.
Until recently, the only evidence that they existed came from
Greek
mythology and the writings of ancient historians. Then, during
expeditions in 1999 and 2000, a team of French marine
archaeologists
headed by Franck Goddio found the ruins-almost completely
intact-buried
on the seafloor of the Abu Qir Bay in Egypt.
Since then, there has been much speculation about why the cities
disappeared so suddenly. Earthquakes, subsistence conditions, and
a rise
in sea level have all been suggested as possibilities.
"There are no written documents on how, when, or why these
two cities
went down," said Jean-Daniel Stanley, a geoarchaeologist
with the
Smithsonian Institution in Washington, D.C.
Stanley and his colleagues at the Institut Européen
d'Archéologie
Sous-Marine in Paris (the European Institute of Marine
Archaeology)
argue that a major flood of the Nile in the middle of the eighth
century
A.D was to blame. The flood, they say, triggered the sinking of
Eastern
Canopus and Herakleion by turning the ground beneath the cities
into
liquefied mud.
The collapse was sudden and catastrophic, said Stanley. "We
can tell,"
he said, "because in both places we've found gold and
jewelry, which, if
there had been time, people would have taken with them when
fleeing."
Gateways to Egypt
Herakleion and East Canopus once stood at the mouth of the
now-extinct
Canopic branch of the Nile. Built sometime between the seventh
and sixth
centuries B.C., as the days of the Egyptian Pharaohs were coming
to an
end, the cities flourished as gateways to Egypt.
Herakleion was a port of entry to Egypt that grew wealthy
collecting
taxes on goods being shipped upriver.
Frozen in time below the waters were many temples and statues of
gods
and goddesses, also attesting to the cities' role as destinations
for
religious pilgrims.
Until the undersea discovery, historians knew about the cities
only
through myth and ancient literature. Menelaus, the king of Sparta
and
husband to Helen, over whom the Trojan War was fought, was said
to have
stayed in Herakleion following the ten-year war against Troy.
Greek mythology holds that the city of Canopus was named after
Menelaus'
helmsman, who was bitten by a viper and transformed into a god.
The Greek historian Herodotus wrote of having visited the cities
in 450
B.C.
The cities' fortunes declined when Alexander the Great founded
Alexandria in 331 B.C. Yet centuries later, Greek geographer
Strabo (63
B.C.-A.D.21 ) described the location and wealth of Herakleion,
while
Seneca (5 B.C.-A.D.65 ) condemned the cities for decadent and
corrupt
lifestyles.
The cities disappeared mysteriously sometime during the eighth
century
A.D.
Dating a Disaster
The cities were found at depths of 20 to 23 feet (6 to 7 meters)
below
the waters of Abu Qir Bay. The ruins of Eastern Canopus are
nearly 1
mile (1.6 kilometers) east of the Aku Qir headland; Herakleion
rests
more than 3 miles (5.4 kilometers) from the shore.
Stanley and his team studied cores from the seafloor,
high-resolution
seismic profiles, and the composition of the substrate-layers of
mud,
shell, silt, and sand deposited over time. From their analysis,
they
concluded that the cities fell when a flood caused the land to
suddenly
liquefy into mud.
Two Arabic coins found at the site date from between A.D. 724 and
743.
Written records that document a major flood of the Nile in A.D.
741 to
742 provide a framework for dating the disappearance of the two
cities.
There are no major earthquakes documented for this period.
Significant flooding not only would cause the river banks to
collapse,
but also would bring heavy loads of sedimentation. This combined
with
the weight of the roiling water could have caused the soft,
unstable mud
on which the cities had been built to liquefy, Stanley and his
colleagues argue in Volume 412 of the journal Nature.
The authors note that similar processes have occurred at the
mouth of
the Mississippi River.
"River mouths shift over time," Stanley explained.
"It's been very
common after bigger floods for the mouth of the Mississippi to
change
drastically. You have liquefaction, slumping riverbanks, and
parts of
land going up and down all over the place."
"Even offshore, two weeks after a major flood," he
added, "you can have
areas that were underwater suddenly above water and other areas
that
were above ground completely underwater."
Copyright 2001, National Geographic
===========
(9) ANTARCTIC SEAFLOOR CORE SUGGESTS EARTH'S ORBITAL OSCILLATIONS
MAY BE
THE KEY TO WHAT CONTROLLED ICE AGES
>From Andrew Yee <ayee@nova.astro.utoronto.ca>
Ohio State University
Contact:
Peter Webb
(614) 292-7285; Webb.3@osu.edu
OSU Department of Geological Sciences at (614) 292-2721
Written by Earle Holland, (614) 292-8384; Holland.8@osu.edu.
Editor's Note: This story embargoed for release until 2 pm ET
Wednesday,
October 17, 2001, to coincide with publication in the journal
Nature.
ANTARCTIC SEAFLOOR CORE SUGGESTS EARTH'S ORBITAL OSCILLATIONS MAY
BE THE
KEY TO WHAT CONTROLLED ICE AGES
COLUMBUS, Ohio -- An international team of scientists reported
this week
that a rock core drilled from the seafloor off the coast of
Antarctica
is the first to show cyclic climate changes in polar regions that
are
linked to cores taken from the ocean bottom in both temperate and
tropical zones.
These records show ice sheet advances and retreats that match
Milankovitch cycles -- variations in the Earth's orbit around the
sun,
in the tilt of the Earth's axis and in the direction the planet's
axis
is pointing. The finding, reported in the British journal Nature,
suggests a link between these orbital oscillations and the timing
of
Antarctic ice ages.
The core was drilled in 1998-99 as part of the Cape Roberts
Project, an
effort by scientists from seven nations to retrieve climate
histories
trapped in millions of years of sediment beneath the floor of the
Ross
Sea. Drill sites located just offshore from the Transantarctic
Mountains
and near McMurdo Station, the main U.S. base in the Antarctic,
have
retrieved cores from three drill holes. The report in Nature
discusses
sediments found in the second of these cores.
While the Antarctic ice sheets formed approximately 34 million
years
ago, the parts of the core described in this paper were deposited
during
a period lasting about 400,000 years, approximately 24.1 to 23.7
million
years ago.
Global temperatures at that time were perhaps 3 to 4 degrees C
higher
than they are today, similar to those predicted for the next
century by
current climate models that incorporate global warming effects.
The
amount of carbon dioxide in the air at that time is believed to
have
been approximately twice current levels.
For years, researchers examining deep-ocean cores from tropical
and
temperate parts of the oceans have used indirect evidence to
propose
that variation in the volume of the ice sheets in the polar
regions was
driven by so-called Milankovitch cycles.
But none of the cores drilled on the Antarctic continental shelf
had
provided the high-quality data needed to rigorously test that
theory.
And interpreting changes in polar climate based on evidence
recovered so
far-removed from the region in question makes many scientists
uneasy.
These new findings, however, show that Antarctic ice sheets
advanced and
retreated at regular intervals during a 400,000-year period
between 24.1
and 23.7 million years ago. The records in the core showed the
cycles
lasted approximately 100,000 years and 40,000 years -- the same
time spans characteristic of some Milankovitch cycles.
"It appears that the Antarctic ice sheet has responded in a
very major
and rhythmic way during this period," explained Peter Webb,
professor of
geological sciences at Ohio State University and co-chief
scientist on
the project. "The growth and reduction of the Antarctic ice
sheet
at its margins is similar to that of the Quaternary Ice Sheets in
the
Northern Hemisphere."
That is important since most scientists believe that the more
recent
formation of the large Quaternary ice sheets, some 2.5 million
years ago
in the Northern Hemisphere, stockpiled water on the continents
and
caused sea levels to drop by as much as several hundred feet.
Webb says
the sea level drop indicated by these new Antarctic core is of
similar
magnitude.
Overall, the Cape Roberts Project cores record approximately 15
million
years of Antarctic history. Within that history, Webb said that
the team
had identified approximately 46 sediment cycles, each of which
contained
a similar pattern of sediment layers. Each records a major
glacial
advance, followed by ice sheet retreat, and concludes when ice
advanced
again from the land into the into the marine continental shelf
area.
"This is exactly what we would expect from a growing and
receding ice
sheet over time," explained Larry Krissek, an associate
professor of
geological sciences at Ohio State and a member of the Cape
Roberts team.
What sets the new finding apart from other work is that the three
sediment sequences described in the Nature paper contained known
time
markers that allowed researchers to date them precisely. The time
markers included deposits of volcanic ash from eruptions of known
dates;
microfossils known to live during a specific period; and episodes
when
the Earth's polarity was reversed -- all elements that helped to
date
the cores. Previous drill cores lacked the precise
dating needed to test any paleoclimatic signal for a potential
Milankovitch effect.
Within the Cape Roberts Project drillcores, researchers
recognized
climate changes that lasted a few tens of thousands of years.
That
observation let them identify climatic variations dating 17 to 34
million years ago. Previously, that kind of change had only been
known
in Antarctic ice cores for only the past half-million years.
Both Krissek and Webb, both researchers with Ohio State's Byrd
Polar
Research Center, were surprised with how rapidly global climate
changed,
based on the sequences in the core. Like evidence from cores
below the
seafloor in the North Atlantic, these segments suggest a
transition from intense glaciations to a wide-scale glacial
retreat may
have taken less than 100 years.
"It should catch people's attention now since the change
appears to
occur in about a human lifespan," Krissek said. Both agree
that the
discovery places polar seafloor core research on a level with
similar
work from sites in the mid-latitudes, a significant
accomplishment given
the short time such work has been underway. Significant seafloor
drilling for climate records only began in 1972.
"We've shown now that the Antarctic continent has a valuable
archival
record," Webb said. "Now we need to go to other parts
of the continent
and see if the entire ice sheet is behaving in this manner, or if
our
new record reflects only a small part of it." He added that
researchers
also must fill in the gap between 17 million years ago and the
present,
a time when the Earth has been considerably colder than the 15
million
years before that.
The Cape Roberts project involves scientists from Australia,
Germany,
Italy, Netherlands, New Zealand, the United Kingdom and the
United
States and is supported by the scientific programs of each of
those
nations. Cores retrieved during the project are divided and
stored at
two sites -- the Alfred Wegener Institut in Bremerhaven, Germany
and
Florida State University.
RELATED WEBSITES
* Table showing geologic time scale. Source: USGS.
http://vulcan.wr.usgs.gov/Glossary/geo_time_scale.html
* Byrd Polar Research Center at Ohio State
http://www-bprc.mps.ohio-state.edu/
* Department of Geological Sciences
http://www.geology.ohio-state.edu/
[NOTE: An image of the Transantarctic Mountains is available at
http://www.osu.edu/researchnews/archive/transantarctics.jpg
(56KB)
A map of Antarctica is available at
http://www.osu.edu/researchnews/archive/antarctica_sm00.jpg
(98KB)]
==============
(10) PANIC COULD BE BIGGEST ILLNESS: PSYCHOLOGICAL DAMAGE AMONG
PEOPLE
COULD BE WIDESPREAD
>From The Guardian, 19 October 2001
http://www.guardian.co.uk/international/story/0,3604,576870,00.html
Sarah Boseley, health editor
Friday October 19, 2001
The Guardian
The threat of chemical and biological weapons could have serious
long-term social and psychological consequences for the
populations of
the US and Europe, leading to widespread anxiety and outbreaks of
panic-induced illness, according to a leading psychiatrist.
Biological agents are ineffective as weapons of war and chemical
weapons
have only limited uses, says Simon Wessely of the Department of
Psychological Medicine at Guy's, King's and St Thomas' School of
Medicine in London and colleagues.
"Instead, chemical and biological weapons are
quintessentially weapons
of terror," they write in this week's British Medical
Journal. Their
purpose "is to wreak destruction via psychological means -
by inducing
fear, confusion and uncertainty in everyday life."
Professor Wessely and colleagues say that civilian populations
may well
respond better than commentators imagine in the face of a genuine
attack
- historically, terror weapons such as aerial bombing have not
led to
panic. But there is evidence, they say, of a psychological
reaction to
the threat of biological warfare. Outbreaks of mass sociogenic
illness,
where people experience genuine symptoms of illness induced by
fear and
anxiety, are already appearing.
"On September 29 2001 paint fumes set off a bioterrorism
scare at a
middle school in Washington state, sending 16 students and a
teacher to
the hospital. On October 3 more than 1,000 students in several
schools
in Manila, Philippines, deluged local clinics with mundane
flu-like
symptoms such as cough, cold and mild fever after rumours spread
that
the symptoms were due to bioterrorism. On October 9 a man sprayed
asubstance into a Maryland subway station, resulting in the
sudden
appearance of nausea, headache and sore throat in 35 people. It
was
later determined that the bottle contained window cleaner,"
they write.
Professor Wessely and colleagues say that the long-term
consequences of
the threat of biological and chemical attack could include
worries about
reproductive outcomes, such as impaired fertility or damaged
babies,
psychological effects and "increased levels of physical
symptoms".
The disruption could be worse than anticipated, they say.
"The general
level of malaise, fear and anxiety may remain high for years,
exacerbating pre-existing psychiatric disorders and further
heightening
the risk of mass sociogenic illness." People will be even
more anxious
because little is known about the potential chronic health
effects of
low-level exposure to the toxic agents that could be used.
Copyright 2001, The Guardian
============================
* LETTERS TO THE MODERATOR *
============================
(11) GIANT IMPACT -- HISTORY OR HOLLYWOOD?
>From Tom Van Flandern <tomvf@metaresearch.org>
Responding to Fred Singer, Uwe Wiechert <wiechert@erdw.ethz.ch>
writes a
nice justification for the "giant impact" hypothesis
for the origin of
our Moon. However, despite the eloquence of his words,
descriptions of a
few key points produce an overview that more accurately describes
the
consensus of scientists than of the data and experimental
evidence.
> [uw to fs]: How do you explain the low density of the Moon
or high
angular momentum of the Earth-Moon system?
Early backwards numerical integrations showed a possible pathway
(with
the aid of tidal friction) from independent orbit to present
orbit via
capture, thereby answering the angular momentum objection.
However, this
orbit requires fine-tuning, and the low density of the Moon is
difficult
to explain via independent evolution, given that it has clearly
been
chemically differentiated. So the capture hypothesis does have
unanswered problems -- but none especially more troublesome than
those
that apply to the giant impact hypothesis.
> [uw]: In the 70ties and 80ties it was justified to decide
between
"co-accretion", "fission", and
"capture" models because these were
"working hypotheses" and scientists collected arguments
for the one or
the other hypothesis.
That is still the case. The "consensus" that has formed
around the giant
impact hypothesis is a cleverly forged political consensus
achieved by
excluding the strongest proponents of alternative viewpoints from
both
of the meetings where such consensus viewpoints were achieved,
and from
their published proceedings. The consensus was further aided by
the
untimely deaths of some of the leading proponents of
alternatives, most
notably O'Keefe and Runcorn. In my opinion, the consensus is
entirely
unjustifiable on physical and observational grounds, as I will
explain.
> [uw]: The "giant impact" theory is a kind of
"unifying theory". The
significance of the oxygen isotopes is that Theia and Earth
formed from
a similar mix of components, if the early solar system was
heterogeneous. This probably requires "co-accretion" of
Theia and the
proto-Earth at a similar heliocentric distance.
Given the heterogeneity of asteroids, Theia must indeed have
formed at a
closely similar distance as Earth. Yet that is precisely what is
forbidden by the laws of dynamics, and is the main
counter-argument
against accretion hypotheses in general. Objects in identical or
closely
similar orbits can neither collide nor have close approaches.
They are
instead forced to librate, just as happens for Trojan asteroids
in
Jupiter's orbit and for co-orbiting moons of Saturn. This is the
same
dynamical mechanism as experienced by astronauts trying to dock
with a
space station. If the capsule is orbiting behind the space
station,
firing capsule thrusters to accelerate forward immediately
increases the
orbital period of the capsule, causing it to fall further back.
Ironically, only a repulsive force or a reverse thrust will allow
the
co-orbiting objects to approach one another.
So any body able to collide with Earth must have a different mean
distance and a higher eccentricity. But then why were the oxygen
isotope
ratios identical for Moon and Earth, with no trace of input from
a third
body?
> [uw]: Most of the Moon formed from the silicate mantle of
Theia but
between 10 to about 30 % material from the Earth's mantle seems
to have
thrown into orbit as well.
This proposal (material from Earth) fights two severe problems
with
physics. The first is that nothing can be placed into Earth orbit
by a
single impulse occurring at points on or below Earth's surface.
The
trajectory resulting from such an impulse has the point of origin
as a
continuing point on the orbital trajectory, meaning that
re-collision
with the Earth before one orbit is complete is inevitable. Hence
no
cannon or asteroid impact can ever place a satellite or ejecta
into
orbit. Rockets launched into orbit must first achieve orbital
altitude,
then fire again sideways to achieve an orbit entirely above the
atmosphere. This is the well-known "two impulse"
requirement. The Theia
scenario lacks a plausible second impulse to allow Earth material
to get
into the Moon.
The second problem is more severe: Material with the strength of
Moon
rocks cannot be accelerated in a single impulse to speeds greater
than
2.8 km/s without being totally vaporized by the shock wave.
Correspondingly, analysis of lunar meteorites recovered on Earth
has
shown that none of them was launched faster than 2.8 km/s from
the Moon.
Yet it takes a speed of no less than 7 km/s to reach and remain
in Earth
orbit -- something unattainable for rock of ordinary strength.
> [uw]: So, also the "fission" hypothesis is not
completely wrong. None
of the classic models can stand on its own, of course, but
aspects of
every hypothesis are required to explain what happened at the
beginning.
This is best unified in the giant impact theory to date.
O'Keefe was the first to solve the angular momentum problem, and
he did
it in support of the fission model. Wanke was the first to report
that
the Tungsten deficiency anomaly for the Earth's crust was shared
by the
Moon, and he did that in support of the fission model as well.
Runcorn's
work resolved other compositional signatures of either or both
bodies in
support of fission. Work by my late colleague, Robert Harrington,
and I
at the U.S. Naval Observatory (summarized in my book, Dark
Matter,
Missing Planets and New Comets, North Atlantic Books, 1993; 2nd
ed.
1999) showed that, of the four models for lunar origin, only the
fission
model can describe the whole scenario without need of miracles
and
without needing to ignore some key observation or to suspend some
law of
physics or dynamics. But I'll save that story for another day and
concentrate on the giant impact hypothesis here.
> [uw]: So, you cannot use oxygen isotopes to decide between
the
"classic" models because an identical oxygen isotopic
composition of
Earth and Moon is consistent with all three hypotheses.
This result is broadly consistent with all three models. But to
have the
oxygen isotopes identical could only have been predicted in
advance with
confidence by the model that asserted the Moon and Earth were
formed
entirely from one body -- the Earth. Any of the models except
fission
could rationalize a small or large difference in oxygen isotope
ratios
as easily as they can assimilate identical ratios because they
have no a
priori reason to require one or the other. Only the fission model
put
itself at risk of falsification by requiring that the ratios had
to be
identical -- and they were. Under the rules of scientific method
to
avoid the bias of everyone interpreting all data in terms of a
favored
model, all models are required to make predictions that
distinguish
themselves from competitor models and place themselves at risk.
Fission
earned credibility points for surviving this test, whereas the
other
models did not.
Other factors that can decide between models are existing
observations
and consistency with the laws of physics and dynamics. Survival
of a
lunar mass during the impact of Theia on Earth requires some
fine-tuning
and substantially more than a Mars-sized body for Theia. The
relative
velocities between Theia and Earth at the point of collision
cannot be
less than 11 km/s, the escape velocity, and is more likely to
exceed 13
km/s because close similarity of orbits is forbidden. The bulk of
the
mass from Theia potentially going into Earth-orbit is the part
that
misses the Earth by more than the distance to the Roche limit
during the
grazing collision [Icarus, v. 126, pp. 126-137 (1997)], but is
ripped
from Theia's body as a major portion of Theia collides with
Earth. It
must be slowed by cohesional forces to a forward speed of less
than 11
km/s, but more than 7 km/s, the speed necessary to stay in orbit.
Fragments that lose too much speed don't stay in orbit; and that
lose
too little speed escape the Earth's gravity. So only fragments
gently
(so as not to vaporize) decelerated to forward speeds in a 4 km/s
range
can stay intact in Earth orbit. This would be a small fraction of
Theia.
In [Nature, v. 389, pp. 327-328 & 353-357 (1997)], we learn
that Theia
must be at least twice the size of Mars, and the computer
simulation
still does not have enough angular momentum to match
observations.
Moreover, material deep inside Theia cannot survive because it is
under
such great pressure that the rock would vaporize when that
pressure was
suddenly released. (For example, inside Earth, rock of the
strength of
Moon rocks at depths below just 40 km would vaporize if suddenly
ejected
into space at any speed.) This factor was not considered in the
computer
simulations, but further increases the required pre-impact size
of
Theia.
The above-mentioned collision-avoidance problem with accreting
bodies in
general, and bodies in similar orbits such as Theia and Earth in
particular, applies in spades to re-accreting the Moon once its
pieces
are ejected into Earth orbit in the giant impact model. The
tendency to
avoid close approaches and to librate basically means that
objects in
similar orbits tend to evolve toward a configuration of
"least
interaction action", to use the name coined by Ovenden. Like
the
particles in Saturn's rings, multiple particles orbit at a
maximal
distance from one another, avoiding all interactions to the
extent
possible. Indeed, the natural tendency of orbital debris is to
reach the
configuration of maximum dispersal -- quite the opposite of a
tendency
to accrete. It would be fair to say that maximum
"entropy" is the
natural order, and that discrete objects in an orbiting ring are
no more
likely to assemble into a single body than are the air molecules
in a
jar. This is further supported by calculations by Canup and
Esposito
[Icarus, v. 119, pp. 427-446 (1996)] showing some of the
difficulties in
forming the Moon by re-accretion. They conclude that
high-angular-momentum collisions seem required, and that the
process
"remains challenging" for theoreticians.
Of course, the proto-Moon fragments following a major collision
are more
likely to have high-eccentricity orbits than circular orbits
anyway, in
which case collisions can routinely occur. However, these are
necessarily collisions at high relative speeds, and are therefore
more
often destructive than accretive. Again, the visible evidence in
the
solar system is numerous cases of planetary rings and asteroid
belts
(inner and outer main belts, Trojan asteroids, and
Trans-Neptunian
Objects), with no visible tendency to reassemble into a single
parent
body. By contrast, fission processes may operate more generally
than
just for the origin of Earth's moon. They have been argued as a
general
formation mechanism for all planets, moons, meteoroids, belts,
and rings
at:
< http://metaresearch.org/solar%20system/origins/original-solar-system.asp
>.
Tom Van Flandern
Meta Research
2001-10-18
============
(12) EDINBURGH'S GREAT CONTRIBUTION TO SPACE PROMOTION
>From Andy Nimmo <andy-nimmo@ntlworld.com>
ESA's Press Release says, "ESA has recently created the
"European Space
City" award to honour a city for exceptional contributions
to the
promotion of European space activities."
Having for some 45 years now, been involved in the
promotion of space
activities in Glasgow (only 40 miles from Edinburgh), very much
including European space activities since the birth of ESA, I
regret
that I am unaware of one of those exceptional contributions made
by
Edinburgh. On many occasions during that time, one or more of the
half
dozen or more pro-space societies based in Glasgow have attempted
to
open branches in Edinburgh, but all such attempts have failed. So
far as
I am aware, there is as yet, not a single space promotion
organization
based in Edinburgh, a city that gives us the impression of having
no
interest in space whatsoever.
It is true that scientific contributions have been made by both
the
Royal Observatory and by Universities in both Edinburgh and
Glasgow, but
most of these seem to have had little to do with either space
promotion
or Europe as such.
With best wishes, Andy Nimmo.
===========
(13) CORRECTIONS/WEB DIRECTIONS/SUGGESTION
>From Andy Smith <astrosafe@yahoo.com>
Hello All,
Please change the ACE number associated with Hale-Bopp
(CCNet108/2001/17
Oct/Item 12/Para 4) from 1 to 10.
Also, here are some additional instructions for locating the
AIAA/UN
Workshop Report....Go to the Web site. Click to your language
flag.
Click to Item V. Scroll to the Report (6th.....), which is near
the end
of the scroll. Click to the Report. Scroll to the Asteroid/Comet
Group
Report.
Notes to NASA JPL/NEO, NASA Ames/NEO, Spaceguard (and all the
little
SG's), Space Shield and other outstanding NEO Web pages....This
would be
a good report to link.
Cheers
Andy Smith
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*
ASTEROID DISCOVERIES MAY OUTPACE ABILITY TO ASSESS THREAT TO
EARTH
>From Space.com, 19 October 2001
http://www.space.com/scienceastronomy/solarsystem/asteroid_toomany_011019-1.html
By Robert Roy Britt
Senior Science Writer
After hunting asteroids for two centuries, astronomers achieved a
minor
milestone earlier this month when the tally of known space rocks
whose
orbits are well established surpassed 30,000, three times the
total less
than 3 years ago.
There was no press release. The people who do the counting are
too busy
for ballyhoo.
And soon they will be busier. The tally is expected to double in
a
matter of months and likely soar a startling six-fold or more
within 3
years. And these are just the well-studied rocks. Roughly 150,000
more
have been spotted but need further study before their orbits can
be
known well enough to put them in the books.
Why the bounty? Telescopes are getting bigger and better, and the
high-tech electronic cameras that record the observations are
able to
see things that were invisible just a few years ago.
As a result, asteroids are being found at such a dramatically
increasing
rate that some astronomers say the discoveries may soon overwhelm
the
ability to properly catalogue the objects and do critical
follow-up
observations that could reveal if an asteroid is on a collision
course
with Earth.
Astronomers stress that there is almost no immediate threat that
the
planet will be hit.
Any large asteroids bearing down on Earth would likely be
discovered
decades in advance, experts say. But smaller objects often go
undetected
and could destroy a city. And no one can say if or when a
surprise
impact might occur.
For now, however, it is the data load that most worries some
astronomers.
Looming bottleneck
Several leading asteroid researchers interviewed by SPACE.com
warned of
a looming bottleneck in the worldwide network of computers and
researchers who determine the future paths of thousands of
asteroids
that are detected every month. One crucial link in the process
depends
mostly on amateur astronomers who help to put together
painstaking
details of an asteroid's path after it has been first spotted.
"The increasing number of new asteroids will eventually
overwhelm
observers who do the follow-up," said Benny Peiser, an
expert on the
threat of asteroids at Liverpool John Moores University in the
United
Kingdom.
The flood of data also could overload the computers and staff of
the
primary international clearinghouse for asteroid information, the
Minor
Planet Center in Cambridge, Massachusetts.
The global asteroid monitoring system is a sometimes-loose
collaboration
of private institutions and government agencies, along with the
amateur
astronomers and several dozen professional asteroid researchers
around
the globe.
The amateur component has developed rapidly over the past decade,
often
on an ad hoc basis.
The professional side of things is marked by frequent
disagreement
between its most fervent and productive asteroid hunters. They
argue
over how much information should be provided to the public and
how
quickly it should be released. They debate definitions,
procedures, and
the fine points of risk assessment.
But the scientists all agree on one thing: Earth will one day be
targeted by a potentially devastating asteroid, and they aim to
avert
disaster by spotting it in advance.
The most worrisome rocks are the big ones: Asteroids larger than
1
kilometer (0.62 miles) across suspected of hitting Earth every
100,000
to 300,000 years, says Michael Paine, a volunteer with Planetary
Society
in Australia. Paine tracks the varying estimates of asteroid
impact
risks made by several research groups. A collision from an object
this
large would rock the planet, disrupt the global climate for years
and
could render some species extinct.
Asteroids 100 meters (328 feet) across or larger slam into the
planet
every 1,000 to 3,000 years, Paine says. Such an event could
eliminate a
city or create a tsunami that might inundate shore communities
and even
large cities along multiple coastlines.
If and when such a calamity is foreseen, precautions could
include
evacuating areas to avoid any local disaster that might be
rendered by a
small asteroid. In the future, a spacecraft might be sent to
destroy or
deflect a larger incoming object, saving the planet Hollywood
style.
Good hunting
The first priority of business on everyone's list is to find more
space
rocks. Lately, this is not a problem, and the success of asteroid
hunters grows more stunning by the month.
The first asteroid, Ceres, was discovered in 1801. It took nearly
200
years -- until 1999 -- for astronomers to find and number the
next 9,999
cousins of Ceres. But with advances in telescope technology and
additional human and optical resources devoted to the task, the
count
has tripled since then. On Oct. 2, it reached 30,716.
"I'm guessing we ought to be up to 200,000 in 2004,"
said Brian Marsden,
who serves in a part-time capacity as director of the Minor
Planet
Center, "assuming we can physically keep up with it."
The center, which operates under the auspices of the
International
Astronomical Union, processes the world's asteroid observations
and
connects major observing programs to the individuals who do
follow-up
observations.
The center processes more than 70,000 observations on a busy day,
Marsden said. The tremendous amount of data stems from this fact:
Although a nearby asteroid can often be recognized from data on a
single
night, some must be observed over several months, even years, to
determine their ultimate path or destination.
In September, a record 1,642 asteroids were officially numbered
by the
Minor Planet Center. But there are many more asteroids that have
been
spotted. In all, some 150,000 are already known. Most of these
have not
been observed well enough to determine their orbits precisely.
Only when
an asteroid's path is pinned down with certainty does it get an
official
number.
To keep up with the growing workload, Marsden and his two
colleagues
frequently put in 16-hour days and work six or seven days a week,
he
said.
Looking for killers
Most asteroids pose no threat to Earth, traveling around the Sun
between
the orbits of Mars and Jupiter. But the gravity of Earth and
other
planets can cause an asteroid's path to change with each orbit.
Of
greatest concern are asteroids 1 kilometer or larger that stray
close
enough to our neck of the solar system that they could one day
cross
paths with the Earth.
Researchers disagree on how many of these Near Earth Asteroids
there
might be, but the leading estimates range from 700 to 1,200.
Roughly 500
have been found, none of which poses a threat anytime in the next
century.
But smaller objects are tougher to spot, and some are discovered
just
days before they pass by Earth.
On Oct. 8 of this year, for example, an asteroid thought to be
between
50 and 100 meters in diameter zoomed by our planet at little more
than
twice the distance to the Moon -- a whisker by the standards of
our
solar system's size. The object was first detected just two days
prior.
Its path was determined only the day before the close encounter.
Search programs "red flag" such nearby objects, which
move more quickly
against the background of stars as compared to more distant
asteroids.
Scientists say it is critical to note these fast-movers and
quickly do
follow-up observations to make sure Earth is not in their sights.
That's where the amateurs come in.
Around 100 highly qualified but unpaid astronomers are often well
equipped and are viewed as every bit as capable as professional
astronomers. But there simply won't be enough of them as the
ability of
professionals to spot smaller asteroids improves and the data
load
grows.
"Sooner or later things are going to come to a crunch,"
Marsden says.
Glitches and Bickering
Marsden is confident that his small crew can keep an eye on
things for now,
but he says more funding is required to hire two more people, as
well as
someone to maintain the sometimes-glitchy computer system that
processes
asteroid data and supplies the follow-up observers with the data
they need
to go hunting.
Delays of 24 hours or more have occasionally occurred in the
past, Marsden
said, due either to computer problems or the fact that he and his
two
colleagues are putting in seven-day weeks in an effort to keep
up.
The growing workload has begun to generate tension and cause
workers to snap
at each other -- something that never used to happen, Marsden
said.
Meanwhile, the Minor Planet Center's funding is dropping. The
bulk of its
money has traditionally come from subscriptions to its
publications of
asteroid data. But with the transformation from printed to
electronic
publishing, fewer research institutions, libraries and individual
astronomers are willing to pay for the data.
NASA provides about half of the center's budget (Marsden's own
salary comes
from his position with the Smithsonian Institution). Yet it is
NASA that
funds many of the major search programs that generate the data
that pours
into the Minor Planet Center.
Other solutions
David Morrison, an asteroid researcher and director of the space
program at
NASA's Ames Research Center in California, agrees that the
increasing pace
of discovery may overwhelm the cadre of amateur astronomers doing
follow-up
observations, no matter how well equipped they might be.
Morrison said that any asteroid aiming for Earth can be
discovered decades
before the impact, assuming it is bright enough to be picked up
with current
search telescopes.
"The problem is not that we won't see it soon enough,"
he said. "The problem
is that we won't spot it at all."
But once an asteroid is discovered, Morrison said, there's no
reason it
can't be properly processed. Morrison thinks management of the
growing
bounty of data needs to extend beyond the Minor Planet Center.
"We'll need to distribute the workload among a number of
international
organizations that already have the capability to process these
data,"
Morrison said.
At least three organizations around the world have the needed
computer
programs. One, in Arizona, is called the Lowell Observatory
Near-Earth-Object Search (LONEOS). Lowell scientists used to
process their
own asteroid data, but a grant that funded the effort was not
renewed. So
now they are forced to forward mostly raw data to the Minor
Planet Center.
Bruce Koehn, a research scientist who does the programming for
the LONEOS
effort, said his colleagues would prefer to process their own
data. He said
there are several reasons why distributing the workload is a good
idea.
"The Minor Planet Center can easily become
overwhelmed," Koehn said.
Equally important, he said, is that having multiple groups do the
calculations provides a check and balance for overall accuracy.
It also
creates an environment where new and improved methods will be
developed by
one group and adopted by others.
Regardless, the future might not be as grim as others think,
according to
Koehn.
Most large asteroid survey programs do some of their own
follow-up work, he
said. As the pace of discovery increases, he thinks these survey
teams will
be forced to do more of their own follow-up. And other search
projects
currently in the planning stages have included follow-up
observing as part
of their strategy, he said.
In addition, two groups currently do some calculations that
contribute to
the overall knowledge base and double-checking. One team is at
the
University of Pisa and another at NASA's Jet Propulsion
Laboratory.
Too many hubs?
Some researchers say the Minor Planet Center should remain the
hub of
asteroid information.
"The Minor Planet Center has the expertise, links and
contacts," said
Jonathan Tate, founder and director of Spaceguard UK, an group
that
advocates increased search efforts. "They are a central
node, and to
distribute this would produce further complications, both
practical and
organizational."
Tate agreed that more funding is needed to allow the center to
keep pace.
One way to cope with the increasing workload is to fund and
foster greater
international cooperation and new search projects, several
experts say.
Efforts are under way to establish a multinational professional
search
program in Europe, says Peiser, the UK researcher. The idea was
jumpstarted
last year when a task force set up by the British government
recommended
sweeping changes to how governments should view the threat of
asteroids.
Among the official recommendations of the task force:
"We suggest that the United Kingdom and other governments,
together with the
International Astronomical Union, NASA and other interested
parties, seek
ways of putting the governance and funding of the Minor Planet
Center on a
robust international footing, including the Center's links to
executive
agencies should a potential threat be found."
The Minor Planet Center has not yet benefited from the call to
action.
Small fish in a big cosmic sea
Meanwhile, astronomers around the world grapple with a simple
fact: They
cannot see most asteroids smaller than 1 kilometer until they are
relatively
nearby. The technology exists, but it has not been devoted to the
task. The
reason goes back to decisions made roughly a decade ago.
Early discussions spearheaded by NASA resulted in the goal of
finding 90
percent of all Near Earth Asteroids in a decade's time.
Scientists talked of
setting the limit lower, to include objects down to 100 meters,
but they
knew that would have meant finding a lower percentage of the many
more
objects they'd be looking for. Several scientists involved in the
discussions argued that the bulk of the danger rests with
asteroids larger
than 1 kilometer anyway.
As Morrison puts it: "Only these can create impacts that
could have global
consequences and perhaps end civilization as we know it."
So NASA funding for asteroid search programs today is driven
primarily by
the goal of finding objects 1 kilometer or larger. Many smaller
objects are
found in the course of these searches. But some researchers think
it is time
to begin focusing on the smaller rocks.
"We need bigger telescopes to come down to the 100-meter
limit," Tate said.
"There is a substantial risk from undetected 100-meter sized
objects."
If Tate gets what he wants, then Marsden's prediction of 200,000
numbered
asteroids by 2004 would later be superseded by quantities about
which no one
is willing to venture a guess. Millions of small asteroids are
thought to
exist.
"Then things will really start booming," Marsden said.
Which would, of course, greatly exacerbate the problem of
follow-up
observations.
"The amateurs doing follow-up are doing sterling work,"
Tate said, "but it
is a bit odd that something as important as this is not a matter
for
official interest."
Copyright 2001, Space.com
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