PLEASE NOTE:
*
CCNet 34/2001, 2 March 2001
---------------------------
THE METEOR-WRONG SONG
By Matthew Genge
Meteor-rite or meteor-wrong?
Here are some clues to go along.
If it was hot to touch, or glowed bright red;
if it smoked or spat, or sizzled or cracked;
if it made a little hole not a great big crater;
then a meteor-wrong you can expect a bit later.
It if fell from the sky, then when all is said,
its usually been thrown from the neighbour's shed.
If it was black as coal, and crumbles like cake,
then don't bet on it being the next Tagish lake.
If it scared their granny in the middle of the night,
with a bang and a flash of strange coloured light;
if they saw it fall as a great glowing ball,
then it probably wasn't a real meteor-rite fall.
Matthew Genge
Natural History Museum
M.Genge@nhm.ac.uk
"Awful weather, an horrific train crash, a rampant disease
threatening the farming industry, an earthquake in Seattle;
whatever
could happen next in this litany of doom? A meteorite hitting the
Earth?
Well, yes. Happily, the extraterrestrial rock that landed
yesterday
morning at the edge of a field in Hopgrove, near York, was not
quite as
large as the one which, 65 million years ago, crashed into what
is
now the Yucatan Peninsula and wiped out the dinosaurs."
--Charles Arthur, The (truly) Independent, 2 March 2001
http://www.independent.co.uk/news/Uk/Science/2001-03/impact020301.shtml
"AMID a winter of national emergencies, perhaps the last
thing that
Britain needed was a visitor from outer space. [...] Dr Phillip
Manning,
keeper of Geology at the Yorkshire Museum in York, said:
"I've never
seen anything like it. It was all caused by an electrical fire
deep
underground. We all thought it was a meteorite - even the Army
said the hole
was from an impact from above not something below ground. We are
quite
happy to have got to the bottom of it and that people have shown
such
an interest. At least if it happens again, we will know what we
are
looking at."
--Nigel Hawkes, The Times, 2 March 2001
http://www.thetimes.co.uk/article/0,,2-92870,00.html
"I'm quite disappointed to discover I've not survived a
meteorite
falling from the skies at the speed of sound. But it will give
someone
a laugh to discover we were all fooled."
--Sylvia Mercer, 1 March 2001
(1) 'METEORITE' FEVER COMES DOWN TO EARTH WITH A BANG
Daily Telegraph, 2 March 2001
(2) GAMMA-RAY READINGS FROM EROS
Andrew Yee <ayee@nova.astro.utoronto.ca>
(3) POOR SCIENCE REPORTING: NEO COMMUNITY RIDICULED FOR JOB WELL
DONE
Andrew Yee <ayee@nova.astro.utoronto.ca>
(4) NEAR-EARTH 'ASTEROID' SURPRISES ASTRONOMERS
Space.com, 1 March 2001
(5) A WORD OR TWO FOR THE FRIENDS OF PLUTO: DEBATE IS OVER
The New York Times, 2 March 2001
(6) BUCKBALLS AND GASES *MAY* MARK MASSIVE EXTINCTION
PSRD DISCOVERIES, 28 February 2001
(7) DOUBTS EMERGE ABOUT P/T IMPACT HYPOTHESIS
Benny J Peiser <b.j.peiser@livjm.ac.uk>
(8) NEW TASK FORCE ON EUROPEAN STATEGY FOR SPACE
ESA <esaweb@esa.int>
(9) THE YORK "METEORITE" AND OTHERS
Andrei Ol'khovatov <olkhovatov@mtu-net.ru>
(10) GEOLOGY KEEPER RUSHED CONCLUSIONS
Ron Baalke <baalke@zagami.jpl.nasa.gov>
(11) "BACKGROUND RADIATION": ANOTHER FALSE ALARM?
Phil Plait <badastro@badastronomy.com>
(12) THE "CHRISTMAS" COMET
Jonathan Shanklin <jdsh@bas.ac.uk>
(13) PALEOECOLOGY & MAMMOTHS
Bas van Geel <vangeel@bio.uva.nl>
=============
(1) 'METEORITE' FEVER COMES DOWN TO EARTH WITH A BANG
From Daily Telegraph, 2 March 2001
http://www.telegraph.co.uk/et?ac=002549632124328&rtmo=weAiMMib&atmo=rrrrrrrq&pg=/et/01/3/2/nufo02.html
By Robert Uhlig, Technology Correspondent
WITH a supersonic boom, a whoosh and a plop, meteorite hysteria
fell to
Earth in a sleepy suburb yesterday morning, leaving a
smouldering, fizzing
hole a few feet from a startled woman walking her dogs.
Sylvia Mercer had her close encounter with an unidentified
heavenly object
in a quiet country lane in Hopgrove, York. "I was walking my
dogs when I
heard two bangs," she said.
"Then there was a rush of wind whistling past my head and a
plopping noise.
I froze in terror and thought my last moments had come. When I
looked at the
ground I saw a smouldering hole.
"There was smoke and noise coming from it and it was making
strange and
frightening sounds. You don't usually expect to get attacked from
outer
space while you are out for a stroll. It is absolutely
amazing." She ran
home to raise the alarm and then returned to cover the 12in-wide
and
5ft-deep hole with a dustbin lid.
Within minutes, police, the Army Bomb Disposal Squad from
Catterick,
university geologists and museum experts from York were rushing
to the
scene. As police sealed off the crater and prepared to evacuate
the area,
meteorite experts at the Natural History Museum in London were
commandeering
cars, ready to race to York to examine what they were promised
was a
brain-sized 12lb lump of primordial space rock.
Phil Manning, keeper of geology at the Yorkshire Museum, was one
of the
first specialists on the scene. He said it was the biggest
meteorite to hit
Britain for 100 years. "The bangs Sylvia heard were sonic
booms. The
meteorite would be travelling at the speed of sound and the
hissing and
popping were caused by the heat it discharged," he said.
A policewoman who was ordering locals to keep away told reporters
that the
hole had certainly been caused by a meteor impact. "We just
cannot attribute
it to anything else." While bomb disposal experts peered
into the hole,
scientists developed theories to explain its strange blue
colouration.
Only the meteor and planetary experts at the Natural History
Museum in
London urged caution at the growing meteorite hysteria. A
mechanical digger
brought in to excavate and retrieve the rock found nothing. And
nine hours
after Mrs Mercer's narrow escape, experts told her that it was
nothing more
than a low-flying clod of earth.
A high-powered electricity cable, buried 3ft deep, had split,
shorted and
blown - causing the gurgling and popping noises. A spokesman for
City of
York council said: "The hole was caused by the earth being
blown out, not by
an object going in at high speed and burying itself. What flew
past Mrs
Mercer's head was nothing more than a big clod of earth."
Last night Mrs Mercer said: "I'm quite disappointed to
discover I've not
survived a meteorite falling from the skies at the speed of
sound. But it
will give someone a laugh to discover we were all fooled."
Copyright 2001, Daily Telegraph
========
(2) GAMMA-RAY READINGS FROM EROS
From Andrew Yee <ayee@nova.astro.utoronto.ca>
Applied Physics Laboratory
Johns Hopkins University
Laurel, Maryland
NEAR image of the day for 2001 Mar 01
Gamma-Ray Readings from Eros
[ http://near.jhuapl.edu/iod/20010301/
]
This chart shows the gamma-ray spectrum from the surface of Eros.
These
scientific data -- the first ever collected on the surface of an
asteroid --
result from 7 days of measurements following NEAR Shoemaker's
historic
landing on February 12.
The gamma-ray instrument has two detectors -- marked above by the
red and
blue traces -- which picked up clear signatures of key elements
in the
composition of Eros. These data, which surpass in quality all the
data
accumulated by this instrument from orbit, will help NEAR
scientists relate
the composition of Eros to that of meteorites that fall to Earth.
Built and managed by The Johns Hopkins University Applied Physics
Laboratory, Laurel, Maryland, NEAR-Shoemaker was the first
spacecraft
launched in NASA's Discovery Program of low-cost, small-scale
planetary
missions. See the NEAR web site for more details, http://near.jhuapl.edu/ .
=========
(3) POOR SCIENCE REPORTING: NEO COMMUNITY RIDICULED FOR JOB WELL
DONE
From Andrew Yee <ayee@nova.astro.utoronto.ca>
[Extracted from inScight, Academic Press,
http://www.academicpress.com/inscight/03012001/graphb.htm
This item is supplied by the AAAS Science News Service.]
Thursday, 1 March 2001, 5 pm PST
Wind Startles Scientists
By MARK SINCELL
The Spacewatch Project, which monitors the ether for possible
Earth-threatening objects, found just what they were looking for,
and
dreading, on 19 February. A telescope on Arizona's Kitt Peak
captured a
bright streak of light in the night sky: an unidentified
automobile-sized
object motoring straight toward Earth. An analysis of the
object's path
showed that it would pass within 0.0039 astronomical units -- or
a scant
500,000 km -- from the home planet.
The Minor Planet Center (MPC) in Cambridge, Massachusetts,
promptly named
the threatening interloper MPEC 2001-D47 and alerted the
astronomical
community, sending several international teams scampering to
their
telescopes.
As the data flowed in, Jon Giorgini and Lance Benner, astronomers
at the Jet
Propulsion Laboratory in Pasadena, California, decided to run the
orbit
analysis backward to figure out where the object had come from.
Judging from
its orbit, 2001-D47 was not a recently arrived asteroid;
rather, it had to
have already made several loops around the Earth-moon system,
including a
near collision with the moon on 19 August 2001.
"At that point we suspected it was manmade," says
Benner. But what? "That
was an easy one," says Jonathan McDowell, an astronomer and
space history
buff at the Harvard-Smithsonian Center for Astrophysics in
Cambridge,
Massachusetts, who pegged it as the WIND satellite, launched in
1994 to
study the solar wind. Scientists sling WIND around the moon to
place it in
different orbits. "It regularly confuses the Near Earth
Object people," says
McDowell, "but this is the first time it ever got [an MPC]
designation."
© 2001 The American Association for the Advancement of Science
==========
(4) NEAR-EARTH 'ASTEROID' SURPRISES ASTRONOMERS
From Space.com, 1 March 2001
http://www.space.com/scienceastronomy/solarsystem/no_asteroid_010301.html
Near-Earth 'Asteroid' Surprises Astronomers
By Robert Roy Britt
While searching for space rocks on Feb. 19, 2001, Robert McMillan
made a
routine discovery of a streak of light in the sky that appeared
to be a
relatively nearby object. McMillan hunts for asteroids that might
collide
with Earth. So following normal procedure, he reported the object
to the
International Astronomical Union's Minor Planet Center.
"I didn't know what the object was at the time of discovery,
only that the
Minor Planet Center's Web site did not list any known minor
planet at that
location," said McMillan, who scans the skies as part of the
Spacewatch
program at the University of Arizona's Lunar and Planetary
Laboratory.
It is important work. If an asteroid is heading our way, we want
to know.
Scientists at the Minor Planet Center were immediately intrigued
by the
object. They calculated where it was headed. The object was about
1.5 lunar
distances from Earth. Anything this close needed to be watched
carefully.
But the scientists were suspicious. Something wasn't right. The
orbit was a
very unlikely one. It even seemed to share characteristics with
Earth's
orbit around the Sun.
"When you have small objects in orbits that resemble the
Earth, there is
always a suspicion that an object is artificial," said
Gareth Williams,
associate director of the Minor Planet Center.
Still, Williams gave the object an official space rock stamp of
approval:
Asteroid 2001 DO47.
Williams said yesterday that in the past, scientists have
complained about
how long it sometimes took to get an object listed, a critical
step to
circulating information so others can turn their telescopes
toward the
potentially dangerous rock and make orbital calculations. Efforts
have been
made to speed up the process since a new staff member was added
midway
through last year.
E-mails flew from coast to coast as researchers discussed the
object's
strange orbit and scrambled to pin it down.
After 2001 DO47 was announced, Jon Giorgini of NASA's Jet
Propulsion
Laboratory looked at the object's orbit. He ran some orbital
solutions on
his computer and determined that it had passed within 6,064 miles
(9,782
kilometers) of the Moon last August. Giorgini also noted that the
orbit was
"difficult to obtain by accident." (Williams called it
"weird.")
It looked like the object might be captured in a temporary Earth
orbit. Sort
of a second moon.
More data arrived on Friday, Feb. 23, and researchers were
anxious. The
object was not behaving as predicted. Nobody needs a near-Earth
asteroid
behaving erratically. But Giorgini and others became more and
more
suspicious that the object might not be a real space rock.
Calculations
continued.
On Sunday at the Minor Planet Center, Williams finally got word
on the true
nature of the object from the local satellite expert Jonathan
McDowell. He
broke the news to his boss, Brian Marsden: "2001 DO47 has
switched on its
engine!"
Williams suggested that confirmation of the presumed engine
firing be
obtained from Giorgini before announcing anything. Giorgini
agreed that an
engine had been activated, and the announcement was made that
2001 D047 was
a machine.
Asteroid 2001 DO47 is actually NASA's WIND spacecraft, launched
in 1994.
NASA says the craft was to go into a "sun-ward, multiple
double-lunar
swing-by orbit ... followed by a halo orbit at the Earth-Sun L-1
(Lagrangian) point."
No wonder it confused researchers.
"We would have liked to check out the artificial possibility
before
announcing the object, but our local ... satellite expert,
Jonathan McDowell
... was away observing in Arizona," Williams said in an
electronic posting
after the object's true identity was revealed.
WIND has tricked scientists before, Williams said, but the last
time around
it didn't undergo any official name changes.
"Part of the problem," Williams told SPACE.com on
Wednesday, is that "many
artificial satellites with highly elliptical orbits [making it
easy to
confuse them with asteroids at certain points in their orbits]
are not
tracked and so orbital elements are not available for them."
Copyright 2001, Space.com
=========
(5) A WORD OR TWO FOR THE FRIENDS OF PLUTO: DEBATE IS OVER
From The New York Times, 2 March 2001
http://www.nytimes.com/2001/03/02/science/02PLUT.html
By KENNETH CHANG
The American Museum of Natural History plans to install a plaque
today to
answer a question often asked by visitors to its Rose Center for
Earth and
Space: "Where's Pluto?"
They're missing Pluto because it has been mentioned only in
passing in the
museum's exhibits. The scientists don't consider it a planet - in
fact, they
don't even consider the term "planet" scientifically
useful.
The scientists hope to clear up any confusion among visitors by
adding the
plaque, and by updating the video kiosks with a discussion of the
current
scientific debate on whether Pluto is a planet or something else.
"The fact people are so interested in it means we have to
answer their
questions and put out more information," said Dr. Michael
Shara, curator of
the museum's astrophysics department. "If it makes people
think, it's a
positive thing."
But the changes do not mean the astrophysicists have changed
their opinions.
"Absolutely not," Dr. Shara said. "What can I tell
you? I don't think Pluto
is a planet."
The Rose Center's "scale walk," which depicts the
relative sizes of objects
in the universe, includes models of the solar system's four inner
terrestrial planets mounted on the handrail and the four gas
giant planets
hanging from the ceiling.
Pluto, an icy body at the outer edge at the solar system and far
smaller
than the eight planets, did not fit into either category and was
left out
when the Rose Center opened a year ago. To some visitors who
recall school
lessons about nine planets in the solar system, the omission has
been
confusing and even distressing.
The new plaque, to be mounted next to the photographs of the
planets, notes
that Pluto shares a similar orbit and composition with a ring of
icy bodies
beyond Neptune known as the Kuiper Belt.
"Some astronomers regard Pluto as a Kuiper Belt object, some
call it a
planet, and others think of it as both," the plaque says.
"This confusion
arises because a consensus has yet to emerge on the scientific
definition of
`planet.' "
A 1.75-inch-wide circle on the plaque shows the relative size of
Pluto,
which is smaller than the Earth's moon.
The kiosk display offers additional information about Pluto and
the Kuiper
(pronounced KY-per) Belt, and presents arguments on both sides.
Dr. Frank Summers, one of the museum's astrophysicists, begins
the segment
by saying that this isn't the first time that scientists have had
to change
their minds about whether an object really is a planet. He
recounts the
story of how the asteroid Ceres was initially counted as a planet
until more
and more asteroids were discovered, and Ceres had to be
recognized for what
it was.
The International Astronomical Union, the pre-eminent
professional society
of astronomers, calls Pluto a planet, as do other major
planetariums and
science museums. Some opponents are quite critical of the Rose
Center
exhibits and even point out that the latest additions reflect
some change in
its position.
"They're doing a little papering over, but they haven't
fixed their
problem," said Dr. S. Alan Stern, director of the Southwest
Research
Institute's space studies department in Boulder, Colo. "You
can see them
breaking into a sweat trying to retain their position and yet
backpedal.
It's a mixed and confusing signal to the public."
The decision not to call Pluto a planet because it does not fall
into
terrestrial and gas giant categories "is really skirting a
very fine line
with the facts," he said.
But "planet" does not have a well-defined scientific
meaning, said Dr. Neil
deGrasse Tyson, director of the museum's Hayden planetarium. For
example,
some suggest that planets are bodies large enough for their
gravity to pull
them into spherical shapes but not large enough to become stars.
But that
definition would include some of the larger asteroids and Kuiper
Belt
objects.
"Our view here is the concept of planet has little to no
scientific meaning
or pedagogical value," Dr. Tyson said.
Instead, the exhibits group the solar system into families: the
terrestrial
planets of Mercury, Venus, Earth and Mars, the asteroid belt
between Mars
and Jupiter, the gas giant planets of Jupiter, Saturn, Uranus and
Neptune,
the Kuiper Belt and the even more distant Oort Cloud of comets.
"Don't count planets," Dr. Tyson said. "Count
families." He said many
prominent planetary scientists, including Dr. Scott Tremaine,
chairman of
the astrophysics department at Princeton University, agree with
the museum's
presentation of the solar system.
"I think the Rose Center has done a real service by focusing
the public's
attention on the fuzzy boundaries between the different
constituents of the
solar system," Dr. Tremaine said.
Both Dr. Shara and Dr. Tyson say they expect that over the next
few years,
surveys of the outer solar system will turn up Kuiper Belt
objects larger
than Pluto.
"By the time they find the 10th one," Dr. Shara said,
"the debate will
become uninteresting."
Copyright 2001, The New York Times
==========
(6) BUCKBALLS AND GASES *MAY* MARK MASSIVE EXTINCTION
From PSRD DISCOVERIES, 28 February 2001
http://www.psrd.hawaii.edu/Feb01/permianImpact.html
Written by G. Jeffrey Taylor
Hawai'i Institute of Geophysics and Planetology
The Permian period ended with a massive extinction event that
might have
lasted only several thousand years. Over 90% of marine species,
70% of
vertebrate land dwellers, and most land plants perished.
Scientists have
proposed several hypotheses to explain this environmental
catastrophe,
including massive volcanic eruptions, meteoroid impact, large
changes in sea
level, and severe climate changes. A huge volcanic complex in
Siberia
occurred at about the time of the extinction (251 million years
ago). Now a
group of scientists led by Luann Becker (University of
Washington, Seattle)
report evidence for an asteroid impact. They discovered
fullerenes
(nicknamed "buckyballs"), which are cage-like carbon
compounds consisting of
60 or more carbon atoms, at the boundary between the Permian and
Triassic
periods. The buckyballs at the Permian-Triassic boundary contain
trapped
helium and argon with isotopic compositions like those in
meteorites called
carbonaceous chondrites, and very different from those on Earth.
This led
Becker and her colleagues to conclude that impact of a
9-kilometer asteroid
deposited the buckyballs. An unanswered question is whether this
impact
caused the mass extinction by itself or did so in collaboration
with the
Siberian volcanism and possibly unrelated climate changes.
Reference:
Becker, Luann, Robert J. Poreda, Andrew G. Hunt, Theodore E.
Bunch, and
Michael Rampino (2001) Impact event at the Permian-Triassic
boundary:
evidence from extraterrestrial noble gases in fullerenes.
Science, vol. 291,
p. 1530-1533.
Impacts and Extinctions: The Dinosaur-Killing Example
Fossil experts recognize the end of the Cretaceous Period by the
extinction
of about half the species on Earth, including the dinosaurs.
Scientists
still debate the cause of this mass extinction, but we now know
that two
dramatic events took place at about the same time, 65 million
years ago:
massive volcanic eruptions and the impact of a large (about 10
kilometers)
asteroid.
The volcanic event took longer than the asteroid impact, but is
nevertheless
very impressive. Layers of lava cover over 500,000 square
kilometers of
India. They might have covered three times as much before
erosion. The total
volume of the lava was an astonishing 8 million cubic kilometers.
That's
enough to cover the state of Texas under a layer of lava about 10
kilometers
thick or the entire surface of the Earth under a meter and a half
of lava.
Rock ages indicate that most of the lava erupted over a period of
about a
million years beginning before and ending after the big
extinction event 65
million years ago.
In 1980, Walter Alvarez and his colleagues at the University of
California,
Berkeley, advanced the idea that an asteroid whacked into the
Earth causing
the end of the Cretaceous Period. They had found exceptionally
high
concentrations of the element iridium at the boundary between the
Cretaceous
and Tertiary periods. Iridium is rare in the crust of the Earth,
but much
higher in abundance in meteorites. This led Alvarez to propose
that the
enrichment is due to an asteroid or comet impact. Since then
geochemists
have found iridium anomalies at the Cretaceous-Tertiary boundary
worldwide.
It is often accompanied by shock-damaged quartz, an unequivocal
indicator of
meteorite impact. To top it off, in 1991 A. R. Hildebrand and his
colleagues
identified the crater buried under a kilometer of sediments.
Called
Chicxulub, it straddles the Yucatan peninsula and the Gulf of
Mexico.
Samples of the impact melt collected by drilling into the crater
give an age
of 65 million years. (For more information about Chicxulub, go to
the
Chicxulub Scientific Drilling Project.)
Last year, Luann Becker (then at the University of Hawai`i),
Robert Poreda
(University of Rochester), and Ted Bunch (NASA Ames Research
Center)
reported finding fullerenes at the Cretaceous-Tertiary boundary.
Fullerenes
are unique carbon molecules with structures that resemble
geodesic domes.
Because of this they were named
"buckministerfullerenes" after R.
Buckminster Fuller, inventor of the geodesic dome. The long name
is usually
shortened to fullerenes or buckyballs. Buckyballs have two
important
properties: they seem to be very stable, even surviving arrival
by impact;
and they have a large volume in their interiors that can trap
gases.
The soccer-ball structures of fullerenes allow the molecules to
trap gases
inside. Luann Becker and her coworkers have found that the gases
in
buckyballs from the Cretaceous-Tertiary and Permian-Triassic
boundaries are
similar to those in extraterrestrial buckyballs.
Measurements of the gases in Bob Poreda's laboratory showed that
the
Cretaceous-Tertiary samples contain helium and argon with
isotopic
abundances like those in meteorites. The compositions are much
different
from those in typical Earth rocks or sediments. In fact, Becker
and her
coworkers argue that the isotopes and the buckyballs that house
them must
have formed in stars, long before our star and its Solar System
formed. In
any case, the discovery of buckyballs and unusual isotopes at the
Cretaceous-Tertiary boundary, where an asteroid impact definitely
took
place, indicates that buckyballs and their gases can be used as a
fingerprint for cometary or asteroidal impact.
Impact at the Permian-Triassic Boundary?
Whatever happened at the end of the Permian Period nearly wiped
out all life
on Earth. Over ninety percent of ocean-dwelling species perished.
Seventy
percent of land species died off. Paleontologists call it
"The Great Dying."
It was Armageddon. It may have been fast, too. Recent work
suggests that it
might have taken only several thousand years, or less--a snap of
the fingers
in geologic time. Some scientists disagree, arguing that it took
half a
million years.
The Permian ended 251 million years ago, at the same time the
huge Siberian
flood basalts formed. These lava flows are not quite as
voluminous as the
Deccan lavas that erupted at the Cretaceous-Tertiary boundary.
Their volume
is a mere 1.5 million cubic kilometers versus 8 million for the
Deccan.
Nevertheless, if spread evenly on the surface of the Earth, they
would make
a layer about 30 centimeters thick. You'd be up to your knees in
lava. Like
the Deccan episode, most of the Siberian lavas erupted during an
interval of
about a million years.
Could there have been an impact at the Permian-Triassic boundary,
too?
Geochemists have searched carefully for iridium anomalies in
places where
the boundary is accessible, but they did not find any enrichments
in
iridium. Nor has anyone found other indicators of impact, such as
shocked
quartz. This has led many investigators to favor volcanism as a
major
contributor to the massive extinction event, but Becker and her
colleagues
put impact back in the running by finding buckyballs with
extraterrestrial
noble gases in them.
To search for the buckyballs, Becker crushed each sample and used
acids to
dissolve most of the rock. She then used organic solvents to
extract
fullerenes from the residue. She found not only buckyballs with
60 carbon
atoms, but those with 70 to 160 carbon atoms as well.
The detection of buckyballs by themselves is ambiguous. They can
be made on
Earth by forest fires. Analysis of samples from just above and
below the
boundary in Japan, China, and Hungary indicate that the
buckyballs are
concentrated there. More importantly, there is a sharp increase
in the
abundance of helium-3 at the boundary. The ratio of helium-3 to
helium-4 is
typical of helium trapped in carbonaceous meteorites, and much
different
from Earth rocks or atmosphere. The ratio of argon-40 to argon-36
is well
below that measured in our atmosphere, and trends towards values
typical of
buckyballs in meteorites. Becker and colleagues conclude that the
gases and
their buckyball containers are extraterrestrial. A big impact
spread them
all over the world.
Buckyballs extracted from sediments at the Permian-Triassic
boundary have
very different abundances of the isotopes of helium and argon
than Earthly
materials, such as the atmosphere. They appear to fall on a line
between
abundances in carbonaceous meteorites and air.
A Tangled Web of Processes?
Becker and her collaborators make an excellent case for an impact
having
taken place at the end of Permian, 251 million years ago.
Certainly more
research needs to be done, especially a search for independent
evidence such
as an enrichment in iridium or the presence of impact-damaged
minerals.
Nevertheless, the case seems strong.
But does it have anything to do with the great extinction at the
Permian-Triassic boundary? That's the big question. It appears
that huge
volcanic eruptions occurred around the same time as the huge
impact. Other
studies show that the end of the Permian was accompanied by an
astonishing
change in sea level--a drop of about 100 meters. Could all these
have
combined to cause life to be almost wiped out? Perhaps the
largest
extinction events happen only when two or more dramatic geologic
events
coincide, such as huge outpourings of lava and the impact of a
large
asteroid.
Impacts of multi-kilometer asteroids are not very common. Neither
is the
formation of flood basalts. Nevertheless, the two could happen at
the same
time surprisingly often. There have been ten huge flood basalt
eruptions on
the continents starting with the Siberian eruptions 251 million
years ago.
Each lasted about one million years (actually somewhat longer,
but the
majority of the lava squirted out in a relatively short span of
time). This
means that for the past 251 million years, large eruptions have
been going
on for 10/251, or 1/25 (4%), of the time. For any random large
impact there
is a 4% chance it will hit during a huge eruption. For two
impacts, the
chance of one of them hitting is double that, 8%.
Studies of the ages of impact craters on Earth and the number of
asteroids
in orbits that cross Earth's orbit indicate that impactors 10
kilometers or
larger hit the Earth once every 100 million years. Thus, during
the past 250
million years, Earth would have been smacked by two or three
10-kilometer
asteroids. The chances are 8 to 12% that one of them would have
corresponded
to a flood basalt eruption. Five-kilometer asteroids hit once
every 6
million years. In this case, it is extremely likely that one will
happen
during a flood basalt eruption. However, impacts of
five-kilometer asteroids
have a much smaller affect on Earth than do larger ones (roughly
in
proportion to the cube of the radius).
This means that we should not be too surprised that both the
Permian-Triassic and Cretaceous-Tertiary extinction events have
both huge
volcanic eruptions and large impacts associated with them. (It
also means
that the impacts did not cause the volcanism, though it does not
rule that
out, of course.) Possibly the largest extinctions occur when two
or more
geologic processes operate at the same time. This would not occur
frequently, and neither do immense extinction events--fortunately
for us.
Acknowledgement: PSRD would like to thank Gerald Fryer and Ralph
Moberly
(both at the University of Hawai`i) for an enlightening email
discussion
about the probabilities of impacts and huge volcanic eruptions
occurring
together.
================
(7) DOUBTS EMERGE ABOUT P/T IMPACT HYPOTHESIS
From Benny J Peiser <b.j.peiser@livjm.ac.uk>
In his presentation at the recent Liverpool Symposium, Iain
Gilmour (Open
University) pointed out that there is no hard evidence for the
existence of
fullerenes at the K/T boundary. A lack of fullerenes in a
confirmed impact
boundary, however, raises serious doubts about whether or not
fullerenes are
an impact signature at all. What is more, according to Iain,
there are
serious doubts about the reliability of the analytical approaches
adopted in
the K/T fullerenes studies as well as in Luann Becker's Laser
Ablation (P/T
and Sudbury). A much more rigorous method, mass spectrometric
analysis,
recently used by R. Taylor and A.K. Abdul-Sada to test the
fullerenes-impact
connection for the K/T event, did not find any support for the
hypothesis:
"Careful re-examination of the Cretacous-Tertiary boundary
layer material
that was reported earlier to contain C-60, confirms that there is
a peak in
the HPLC of the extract having a retention time similar to that
of C-60 (the
basis of the earlier claim). However, mass spectrometric analysis
shows this
to be merely a mixture of hydrocarbons. No traces of either C-60
or C-70 are
present under conditions capable of detecting as little as 50 pg
(0.001 part
per billion in the original material), this sensitivity being
four times
greater than that given in the earlier report. These findings are
entirely
consistent with the known high oxidative instability of
fullerenes." (R.
Taylor and A.K. Abdul-Sada (2000), There are no fullerenes in the
K-T
boundary layer, Fullerene Science and Technology 8(1-2), 47-54).
I think Iain Gilmour is right to ask for more convincing evidence
- in
particular evidence of shocked materials - before he is prepared
to accept
the rather weak P/T impact hypothesis.
BJP
=========
(8) NEW TASK FORCE ON EUROPEAN STATEGY FOR SPACE
From ESA <esaweb@esa.int>
ESA Press Release, Nr. 12-2001 - Paris, 1 March 2001
ESA-EC Joint Task Force on European Strategy for Space meets for
the first
time in Brussels
Today ESA and the EC have set up a Joint Task Force to implement
the
European Strategy for Space endorsed by the European Research
Council and by
ESA's Council at Ministerial level in Brussels on 16 November
2000 (see ESA
press release N° 74-2000 of 16/11/2000).
The main objectives of the European Strategy for Space - jointly
prepared by
the EC and ESA - are (1) to strengthen the foundation for space
activities
in Europe, (2) to enhance scientific knowledge for a better
understanding of
our planet, the solar system and the Universe, and (3) to reap
the benefits
for markets and society through exploitation of technical space
capabilities.
The main missions of the Joint Task Force are to monitor the
implementation
of this strategy, to propose a framework enabling ESA to act as
implementing
agency with respect to EU policy on space, and to prepare a
report on
European space activities for submission to the EU and ESA
Councils and the
European Parliament by the end of 2001.
At today's meeting the work plan for the coming year was
endorsed. The
group's first concrete activities consist of a thorough analysis
of the
present situation concerning the Galileo project and a common
effort to
deepen the initiative for Global Monitoring for Environment and
Security
(GMES).
On this occasion, Antonio Rodotŕ, Director General of ESA, made
the
following statement: "The Joint Task Force is continuing and
developing our
shared effort in 2000, effort which led to joint endorsement of
the European
Strategy for Space by the ESA and EU Councils. With the Joint
Task Force,
Europe is taking another step towards a new era in which space
systems will
become an integral part of the overall political and economic
drive to
promote the interests of Europe's citizens".
On the EU side the Research Commissioner, Philippe Busquin,
declared :"The
set-up and work of this Joint Task Force illustrate the role that
I see for
the Commission in developing a true space policy for Europe and
in getting
everyone to work together around common goals. It is a concrete
step in
building a European Research Area, in a field that is of
strategic interest
to Europe and can bring concrete benefits to citizens, for
example in
improved monitoring of our environment or a more efficient
transport system".
For additional information:
Géraldine Naja
ESA, Directorate of Strategy
Tel: +33.1.53.69.69.75
Fax: +33.1.53.69.7382
e-mail : geraldine.naja@esa.int
For more information on ESA, visit our web site at : www.esa.int
============================
* LETTERS TO THE MODERATOR *
============================
(9) THE YORK "METEORITE" AND OTHERS
From Andrei Ol'khovatov <olkhovatov@mtu-net.ru>
Dear Dr. Peiser, and All,
I would like to make a methodological comment regarding the
latest York
"meteorite" story.
Besides magic power of electric phenomena, the story reveals some
tendency
of practically automatically attribution of almost every
event associated
with "something flew or exploded" to a "meteorite
fall". Another good
example is the Dec.7, 1999 Guyra, Australia "meteorite
fall", which later
was discovered to be terrestrial origin (see:
www.geocities.com/olkhov/gr1997.htm#13).
Initially just a few experts
doubted that it was a meteorite fall. It is also possible to
recall the
Dec.4, 2000 Salisbury, USA "meteorite" fall, having
nothing to do with a
meteorite. Our Nature is much more complex (and interesting), and
we should
not forget about this.
Sincerely,
Andrei Ol'khovatov
Moscow, Russia
=============
(10) GEOLOGY KEEPER RUSHED CONCLUSIONS
From Ron Baalke <baalke@zagami.jpl.nasa.gov>
> SPACE ROCK FALLS ON YORK
>
> >From BBC, 1 March 2001 (16.00 GMT)
> http://news.bbc.co.uk/hi/english/sci/tech/newsid_1196000/1196688.stm
>
> A meteoroid has landed in a field in York, UK, narrowly
missing a woman
> walking her two dogs.
> Officials from the Yorkshire Museum have confirmed it was
made by a rock
> falling from space. It is almost 10 years since any such
similar event
> has been recorded on the UK mainland.
Hmmm...I'm curious how they confirmed it was a meteorite when no
rock was
recovered. Also, they have now determined that the hole was
created when an
underground electrical cable short-circuited. See the updated BBC
article:
from BBC, 1 March 2001 (16.06 GMT)
http://news.bbc.co.uk/hi/english/sci/tech/newsid_1196000/1196688.stm
===========
(11) "BACKGROUND RADIATION": ANOTHER FALSE ALARM?
From Phil Plait <badastro@badastronomy.com>
AHA! The electric cable snapping would explain the smoke too.
That was
bothering me; meteorites are usually cold when they hit, so there
shouldn't
be smoke.
I am still baffled by the claim of "background
radiation", and why that
would make a sound. Another flase alarm?
-Phil
The Bad Astronomer
================
(12) THE "CHRISTMAS" COMET
From Jonathan Shanklin <jdsh@bas.ac.uk>
Dear Benny,
Readers might also like to look at
http://cfa-www.harvard.edu/cfa/ps/Ephemerides/Comets/2000WM1.html
and the
associated magnitude estimates. This ephemeris uses m = 6.5 + 5
log d + 10
log r (ie n = 4) and predicts that the comet will be closest to
the Earth on
December 2 at a distance of 0.32 AU; it also predicts that the
comet will be
brightest at 4th magnitude, on January 18 a few days before
perihelion.
Recent CCD magnitude estimates are broadly consistent with the
ephemeris, at
around 17th magnitude. It should also be noted that the IAU
are considering
using n=3 for routine prediction of comet brightness. It is
unusual for a
long period comet to brighten as rapidly as n=7, though some
comets do have
an even higher coefficient. Generally CCD magnitudes for distant,
well
condensed comets are in good agreement with visual estimates,
though this is
not the case for diffuse objects that are closer to the Earth.
I appreciate that in order to attract media attention it is
necessary to
give objects a catchy title, however this object is not brightest
at
Christmas, it is not most easily visible at Christmas, it was not
discovered
at Christmas, it is not closest to the Earth at Christmas and it
is not
closest to the Sun at Christmas. The phase angle is greatest
within a week
of Christmas, but this is unlikely to be of significance to the
public.
Given that it will be another six months before we can begin to
say with any
confidence how it might behave, and that it is not impossible
that other
objects will be discovered, it is a little premature to give the
comet the
title 'Christmas comet'.
I quoted comet Kohoutek at least in part because this is the best
known
example of media hype. It would be unfortunate if the same
thing happened
with this comet.
Jonathan Shanklin
j.shanklin@bas.ac.uk
British Astronomical Association, Comet Section
http://www.ast.cam.ac.uk/~jds
===========
(13) PALEOECOLOGY & MAMMOTHS
From Bas van Geel <vangeel@bio.uva.nl>
Dear colleagues,
March 11th (20.00 or 21.00) the film 'Land of the Mammoth' will
be aired by
Discovery Channel. Part of the film will be about the environment
of the
'Jarkov Mammoth' (reconstruction based on the study of fossil
pollen, seeds
and mosses by Bas van Geel, Jan Peter Pals and Guido van Reenen).
The Jarkov
Mammoth (which lived ca 24000 years ago) was recently found in
permafrost on
the Taymyr Peninsula (N-Siberia). The main conclusions of the
study were:
the climate in N-Siberia during the coldest part of the last Ice
Age was
very dry. The mammoth and contemporaneous large herbivores were
living in a
steppe, dominated by grasses and Artemisia. The reconstruction of
the
vegetation is confirmed by palynological studies of lake
deposits, published
by colleagues in Potsdam.
Best wishes,
Bas van Geel
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*
THE COMET/ASTEROID IMPACT HAZARD: A SYSTEMS APPROACH
From David Morrison <dmorrison@arc.nasa.gov>
NEO News (01/03/01) Chapman White Paper
Dear Friends & Students of NEOs:
This edition of NEO News features a new "white paper"
on the NEO
impact hazard by Clark Chapman, Dan Durda, and Robert Gold. I
have
reproduced here only the Executive Summary, Introduction, and
Recommendations. The full paper, including table and references,
is
available on the Web at
(http://www.boulder.swri.edu/clark/neowp.html).
Also included in this message is an announcement of a community
forum
this month on the proposed NASA Dawn mission to orbit main-belt
asteroids Ceres and Vesta.
David Morrison
================================================
THE COMET/ASTEROID IMPACT HAZARD: A SYSTEMS APPROACH
Clark R. Chapman and Daniel D. Durda
Office of Space Studies
Southwest Research Institute
Boulder CO 80302
Robert E. Gold
Space Engineering and Technology Branch
Johns Hopkins University Applied Physics Laboratory
Laurel MD 20723
24 February 2001
EXECUTIVE SUMMARY
The threat of impact on Earth of an asteroid or comet,
while of very low probability, has the potential to create public
panic and -- should an impact happen -- be sufficiently
destructive
(perhaps on a global scale) that an integrated approach to the
science, technology, and public policy aspects of the impact
hazard
is warranted. This report outlines the breadth of the
issues that
need to be addressed, in an integrated way, in order for society
to
deal with the impact hazard responsibly. At the present
time, the
hazard is often treated -- if treated at all -- in a haphazard
and
unbalanced way.
Most analysis so far has emphasized telescopic searches
for large (>1 km diameter) near-Earth asteroids and
space-operations
approaches to deflecting any such body that threatens to
impact.
Comparatively little attention has been given to other essential
elements of addressing and mitigating this hazard. For
example, no
formal linkages exist between the astronomers who would announce
discovery of a threatening asteroid and the several national
(civilian or military) agencies that might undertake
deflection.
Beyond that, comparatively little attention has been devoted to
finding or dealing with other potential impactors, including
asteroids smaller than 1 km or long-period comets. And
essentially
no analysis has been done of how to mitigate other repercussions
from
predictions of impacts (civil panic), how to plan for other kinds
of
mitigation besides deflection (e.g. evacuation of ground zero,
storing up food in the case of a worldwide breakdown of
agriculture,
etc.), or how to coordinate responses to impact predictions among
agencies within a single nation or among nations.
We outline the nature of the impact hazard and the
existing ways that a predicted impact would be handled at the
present
time. We describe potential solutions to existing gaps in
the
required approaches and structures (both technical and
governmental)
for dealing with impacts, including the kinds of communications
links
that need to be established and responsibilities assigned.
We recommend crafting, adoption, and implementation of
improved procedures for informing the broader society about the
impact hazard, notifying the public and relevant
officials/agencies
about an impact prediction, and putting in place (in advance of
such
predictions) procedures for coordination among relevant agencies
and
countries. We recommend that pro-active steps be taken,
perhaps
through a high-visibility international conference and other
types of
communication, to educate the broader technical community and
public
policy makers about the impact hazard and the special aspects of
mitigating this atypical hazard. For example, the most
likely
international disaster that would result from an impact is an
unprecedentedly large tsunami; yet those entities and individuals
responsible for warning, or heeding warnings, about tsunamis are
generally unaware of impact-induced tsunamis. We also
recommend that
additional attention be given to certain technical features of
the
hazard that have not received priority so far, including the need
to
discover and plan mitigation for asteroids smaller than 1 km and
for
comets, study of the potential use of space-based technologies
for
detection of some kinds of Near-Earth Objects, study of chemical
rockets as an approach to deflection that is intermediate between
bombs and low-thrust propulsion, and further evaluation of the
risks
of disruption (rather than intended deflection) of an oncoming
object.
Finally, we believe that international human society (and
elements of it, like the U.S. government) needs to make an
informed,
formal judgement about the seriousness of the impact hazard and
the
degree to which resources should be spent toward taking steps to
address, and plan for mitigation of, potential cosmic
impacts. The
existing unbalanced, haphazard responses to the impact hazard
represent an implicit judgement; but that judgement does not
responsibly address the extraordinary and unusual consequences to
nations, or even civilization, that could result from leaving
this
hazard unaddressed in such an arbitrary, off-hand way. For
example,
we believe it is appropriate, in the United States, that the
National
Research Council develop a technical assessment of the impact
hazard
that could serve as a basis for developing a broader consensus
among
the public, policy officials, and governmental agencies about how
to
proceed. The dinosaurs could not evaluate and mitigate the
natural
forces that exterminated them, but human beings have the
intelligence
to do so.
{This SWRI White Paper is also available at:
www.boulder.swri.edu/clark/neowp.html}
INTRODUCTION
The impact hazard from near-Earth asteroids and comets
has evolved from a science fiction scenario to a serious societal
issue during the past twenty-five years. The scientific
community
began to understand the implications for life on Earth of errant
small bodies in the inner solar system in 1980 when Nobel
Laureate
Luis Alvarez and his colleagues published an epochal paper in
Science
(Alvarez et al. 1980) advocating asteroid impact as the cause of
the
great mass extinction 65 million years ago that led to the
proliferation of mammal species. The same year, the NASA
Advisory
Council advocated study of a modern-day cosmic threat to
civilization, leading to a formal study (The Spacewatch Workshop,
chaired by Eugene Shoemaker) the following year.
A decade later, these scientific issues first received
significant public consideration when lobbying efforts by the
American Institute of Aeronautics and Astronautics (AIAA) and
others
resulted in action by the U.S. House of Representatives, which
directed NASA to study the impact hazard. NASA responded by
organizing an International Conference on Near-Earth Asteroids
and
two study workshops, one (chaired by David Morrison) leading to
recommendations (Morrison 1992) for a telescopic "Spaceguard
Survey"
of the larger Near Earth Asteroids (NEAs) and the second (chaired
by
John Rather) evaluating a host of potential approaches to
mitigation
of an impending hazard should an asteroid be found to be on a
collision course with Earth (Rather et al. 1992).
During the 1990s, numerous scientific and engineering
conferences have been held worldwide concerning the impact hazard
(including one held at United Nations headquarters, Remo 1997)
and
public interest groups were established in several nations,
mostly
associated with the Spaceguard Foundation
(http://spaceguard.ias.rm.cnr.it/SGF/).
Despite official notice
being taken by several national and international entities (e.g.
the
Council of Europe), little serious attention has yet been given
by
governments to evaluation of the NEO hazard or preparations for
dealing it (NEO = Near Earth Objects, including comets in
addition to
NEAs). NASA, in collaboration with the U.S. Air Force, is
the major
supporter of NEO research, with a few million dollars per year
devoted almost solely to the use of existing telescopes to search
for, and find by 2008, 90% of the NEAs larger than 1 km diameter
(http://neo.jpl.nasa.gov).
In late 2000, a task force recommended
that the British government consider taking initial steps to
support
efforts to research the impact hazard (Atkinson 2000;
http://www.nearearthobjects.co.uk/index.cfm);
in late February 2001,
however, the government responded not with concrete action but
only
promising to study the matter further and formulate an
international
approach to the issue.
Other major elements of the impact hazard remain
unaddressed. Searches for comets and for smaller NEAs are
in their
infancy. And little or no serious, official actions have
been taken
by governments to be prepared to respond to any announcement of a
specific impact threatened in the years or decades ahead.
For
example, Dr. Brian Marsden, who directs the International
Astronomical Union's Minor Planet Center (where most astronomical
data concerning NEOs is cataloged:
http://cfa-www.harvard.edu/cfa/ps/mpc.html),
recently said that he
had no idea who in the United States government would be
receptive to serious information he might have one day about an
impending impact. Surely some agencies would be interested,
but
communication pathways, responsibilities, and implementation
plans
have yet to be established.
This White Paper has been supported primarily by a
Presidential Discretionary Internal Research and Development
grant
from Southwest Research Institute. Its purpose is to
outline
elements of a systematic approach, with various options, for
dealing
with the full breadth of the impact hazard -- starting with
issues
about discovery of potentially dangerous bodies, proceeding
through
societal issues about evaluating the hazard and taking
appropriate
advance measures, to actual mitigation of potentially threatening
impactors. We conclude with some recommendations that might
lead to
a more comprehensive and balanced approach for
twenty-first-century
society to take toward a very real, if low probability, threat
that
could conceivably doom everyone we know and everything we care
about.
DETECTION AND IMPACT EFFECTS (omitted here)
EVALUATION AND WARNING (omitted here)
MITIGATION (omitted here)
RECOMMENDATIONS
Our primary recommendation is that much broader groups of
people need to be educated about impact hazard issues, beyond the
superficial and often incorrect impressions they may have gotten
from
their chief exposures to these matters: exaggerated/retracted
news
stories about impact predictions and "near misses," and
movies like
"Armageddon." A much broader segment of the
technical community,
beyond astronomers and space engineers, needs to appreciate and
become familiar with technical aspects of this hazard.
These
segments include the natural hazards community and experts in
risk
assessment, meteorological storms, seismicity, climate modelling,
etc. In addition, public officials responsible for
mitigation of
(and response to) emergencies and disasters need to understand
the
basic attributes of the impact hazard. These include the
chains-of-command in the military and in the
law-enforcement/civil
defense infrastructures.
Research, planning, and preparation need to commence now,
although it remains to be determined how far such activities
should
go, given the low probabilities of having to address any real,
major
impacts in our lifetimes. We believe that several issues
need to be
addressed in the near future.
* The notification system (concerning a predicted potential
impact)
needs to be cleaned up, expanded, and officially adopted and
implemented.
* Official clearinghouse/s for the best information need do
be
developed (potential nuclei for such functions, including
fledgling
web sites or analogous capabilities, already exist at Jet
Propulsion
Laboratory, NOAA, Spaceguard Foundation, and the IAU Minor Planet
Center, among others).
* Serious connections need to be developed with the hazard
mitigation community, including agencies like FEMA.
* More objective approaches to communications need to be
developed
to minimize misunderstanding of this hazard, which is so
mismatched
to our personal experience base (extreme rarity or low chances of
happening vs. extreme potential consequences). In other
words, the
Torino Impact Hazard Scale needs to be further developed,
extended,
distributed, and explained.
* Official international channels for exchanging
information about
NEO hazard-related issues and events need to be developed.
* Within the United States, an interagency approach, and
assignment
of responsibilities, for dealing with the NEO hazard needs to be
developed; the Global Change Program may provide a
template.
Analogous steps need to be developed in other nations and to
coordinate among nations.
* Education about the NEO hazard would be facilitated by
conducting
a high-visibility, international conference on the NEO hazard,
emphasizing the non-astronomical, non-NEO-deflection issues that
have
so far been treated as backwater concerns in previous NEO hazard
conferences. Perhaps a newsletter should be instituted.
* Given widespread interest in extending the Spaceguard
search down
to bodies much smaller than the 1 km goal of the U.S. search
efforts,
a thorough evaluation of ground- vs space-based approaches needs
to
be made. Although spacebased efforts are usually vastly
more
expensive, they have advantages that may balance the costs in
some
cases; in other cases, the cost of spacebased efforts may not be
relevant (e.g. the searches may be piggy-backed onto other
endeavors
that pay most of the costs).
* We consider the case of comets to be astonishingly
intractable
(they are difficult to detect, there is a short time between
detection and impact so the object can't be studied carefully, a
comet may be difficult or time-consuming to get to so it may not
be
possible to "blast" it until it is almost here, a
comet's motion is
difficult to predict, and the structural nature of comets is
poorly
known -- they break-up independently and unpredictably). So
we
recommend more detailed study of the nature of comets and of
cometary
detection/mitigation strategies. At a minimum, we must
quickly
assess how large a part of the impact hazard comets are.
* Chemical rockets may have quite wide applicability to
deflection
scenarios; we recommend more study of that technology.
* In certain cases of attempted mitigation, disruption is
more
likely than deflection. More research needs to be done in
this area,
including studies of the potential consequences of disruption.
* All of these recommendations are predicated on a
political
decision about the importance of the NEO hazard and about the
level-of-effort that should be expended in addressing it.
The
technical community needs to identify potential criteria (beyond
simple comparisons of death rates from various hazards) for
making
this judgement. We recommend that official, objective
study/ies by
bodies like the National Research Council be done for this
purpose.
Ultimately, society's decision about how seriously to address the
impact hazard will have to involve broad segments of the public,
beyond the technical community.
REFERENCES (omitted here)
TABLE (omitted here)
===============================================
PROPOSED DAWN MISSION TO CERES & VESTA
from Chris Russell
Community Forum - March 11 on Dawn: A Discovery Mission to Vesta
and Ceres
NASA has selected the proposed Dawn Discovery mission for a
concept
study leading to a Step 2 proposal. Dawn uses solar electric
propulsion to fly to both Vesta and Ceres orbiting each for a
period
of nine months. The spacecraft carries a framing camera, a
mapping
spectrometer, a gamma ray/neutron spectrometer, a laser altimeter
and
a magnetometer. Vesta is a dry, differentiated asteroid with a
basaltic crust and is the presumed parent body of the HED
meteorites.
Ceres appears to be wet and have less distinct features. It has
no
known associated meteorites. It has been postulated that Vesta
accreted dry and Ceres wet and that the water kept Ceres cool
enough
to avoid differentiation. Thus these two asteroidal neighbors
represent two quite different end members of solar system
evolution.
The top level science objectives, the measurement suite, and the
science team were approved during the Step 1 selection process.
Over
the next several months the Dawn team will demonstrate to NASA
that
we can safely achieve those objectives within the constraints of
the
Discovery program. It is the intent of the Dawn science team to
engage the scientific community throughout the mission, with
community forums on our plans as we build the spacecraft and
instruments, and with participating scientist programs and data
analysis programs when we are obtaining data. The first community
forum will be held in Houston, TX on Sunday, March 11, 2001 from
1:00
to 4:00 p.m. in Admiral Room A at the Hilton Nassau Bay Hotel
across
from the Johnson Space Center. The purpose of this meeting is
both to
inform the community of our plans and to initiate meaningful
interactions as we execute the various mission phases. If you
wish to
make a formal presentation, please contact amcglynn@igpp.ucla.ed!
u by March 1, 2001.
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