PLEASE NOTE:
*
CCNet 69/2002 - 17 June 2002
----------------------------
"If a huge meteor similar to one that struck Earth 100 years
ago
were to fall on New York City, it could bankrupt every insurance
company in the world, said Bob Hartwig, chief economist for the
Insurance
Information Institute in New York. "The reason for that is
because the
damage can range from the little pieces that hit the roofs of
houses every
night to something that wipes out the species, in which case
we're off the
hook," he said. "I could think of a lot of bad things
that could
happen, but this is No. 1. You can't rule it out."
--Walter C. Jones, The Augusta Chronicle, 16 June 2002
"Dr Steel said that astronomers want to understand the
sudden
outbursts of vapour emitted by comets as they approach the sun,
which
can nudge a comet off a safe orbit around the sun and onto
collision
course with Earth. "These make it virtually impossible to
predict when an
impact with a comet could take place," he said. Dr Steel
added that studies
of the comet core are also crucial for preparing plans to deflect
threatening comets away from Earth. "Some theories predict
that the core
is covered with a black, tarry substance," said Dr Steel.
"It may be
possible to puncture this with projectiles, and release vapour
that can
deflect the comet."
--Robert Matthews, The Sunday Telegraph, 16 June 2002
(1) NASA MISSION TO FIND WHAT LIES AT A COMET'S HEART
The Sunday Telegraph, 16 June 2002
(2) PRESTO, CHANGE-O! COSMIC IMPACTS TRANSFORM EARTH'S SURFACE IN
AN INSTANT
Science News, 15 June 2002
(3) IMPACT CRATERING: BRIDGING THE GAP BETWEEN MODELING AND
OBSERVATIONS
Ron Baalke <baalke@jpl.nasa.gov>
(4) JAPAN INVITES THE MASSES TO LAND ON ASTEROID
CNN, 14 June 2002
(5) SCIENTISTS GATHER THIS FALL TO STUDY PREVENTING AN ASTEROID
STRIKE ON
EARTH
Pittsburgh Post-Gazette, 17 June 2002
(6) GOOD NEWS FOR PLANETARY DEFENSE: ANTI-MISSILE TECHNOLOGY
IMPROVING
STEADILY
BBC News Online, 14 June 2002
(7) MISCELLANEOUS ITEMS AND COMMENT ON CONTOUR
E.P. Grondine <epgrondine@hotmail.com>
(8) AND FINALLY: DOOMSDAY ASTROLOGERS GET IT WRONG - FOR NOW
The Daily Telegraph, 8 June 2002
===============
(1) NASA MISSION TO FIND WHAT LIES AT A COMET'S HEART
>From The Sunday Telegraph, 16 June 2002
http://www.telegraph.co.uk/news/main.jhtml?xml=/news/2002/06/16/ncomet16.xml&sSheet=/news/2002/06/16/ixhome.html
By Robert Matthews, Science Correspondent
Nasa scientists are to launch their most ambitious attempt to
investigate a
comet in a mission that could help to defend Earth against
catastrophic
impacts with matter from deep space.
An unmanned space probe will blast off next month in an effort to
take the
first ever samples of material from a comet's core, affording
scientists a
greater understanding of the mysteries of the mountain-sized
chunks of
primordial matter.
The £100 million probe, called Contour, will come within 50
miles of the
core of Encke, a comet that orbits the Sun between Jupiter and
Mercury and
cuts across the Earth's path twice each year.
Astronomers believe that debris from Encke has struck the Earth
with the
violence of a nuclear explosion several times in the past. The
most recent
impact is thought to have occurred in June 1908, devastating
hundreds of
square miles of Siberia.
Some also argue that Encke is just one fragment of a massive
"mother comet"
which disintegrated thousands of years ago: other fragments may
also have
struck Earth with devastating effect in prehistoric times.
Unlike asteroids, which are made up largely of rock and orbit
mainly between
Mars and Jupiter, comets appear in the Solar System almost at
random.
Mystery surrounds their composition and the internal explosions
which can
tear them apart or cause them suddenly to change direction.
Exploring these phenomena will help researchers to devise methods
to destroy
or deflect comets that are headed towards Earth. "Comets are
the Solar
System's smallest bodies, but among its biggest mysteries,"
said Dr Joseph
Veverka, the principal investigator for the mission.
"We believe they hold the most primitive materials in the
Solar System and
that they played a role in shaping some of the planets, but we
really have
more ideas about comets than facts. Contour will change that by
coming
closer to a comet nucleus than any spacecraft before."
The probe's four scientific instruments will take pictures
showing features
on the comets as small as four yards across, and take
measurements and
samples to show scientists the composition of comet cores.
Samples will be
remotely analysed on board and the results sent back to Earth by
radio
transmission.
After its rendezvous with Encke in November next year, Contour
will travel
on to an encounter with a second comet, Schwassmann-Wachmann 3 in
June 2006.
Unlike Encke, which has orbited the sun for centuries,
Schwassmann-Wachmann
3 was discovered only 70 years ago, and then broke apart,
probably exposing
pristine material from deep inside its core.
According to Dr Duncan Steel, an authority on comets at Salford
University,
Contour's findings from these two comets will play a key role in
defending
the Earth from future impacts. He said: "If we are going to
protect
ourselves, we need to know the nature of these beasts."
Dr Steel said that astronomers want to understand the sudden
outbursts of
vapour emitted by comets as they approach the sun, which can
nudge a comet
off a safe orbit around the sun and onto collision course with
Earth. "These
make it virtually impossible to predict when an impact with a
comet could
take place," he said.
Dr Steel added that studies of the comet core are also crucial
for preparing
plans to deflect threatening comets away from Earth. "Some
theories predict
that the core is covered with a black, tarry substance,"
said Dr Steel. "It
may be possible to puncture this with projectiles, and release
vapour that
can deflect the comet."
The results from Contour's encounter with Encke are also eagerly
awaited by
Prof William Napier, a comet expert at Armagh Observatory in
Northern
Ireland. In the 1980s, Prof Napier and his colleague Dr Victor
Clube of
Oxford University suggested that Encke was just a small fragment
of a far
larger comet that entered the solar system thousands of years
ago.
Evidence for the existence of this 50-mile-wide "mother
comet" first emerged
in 1983, when a satellite detected a vast trail of dust and
debris around
the orbit of Encke. Computer simulations showed that the trail is
consistent
with the break-up of a giant comet about 20,000 years ago, with
the debris
spreading out under the gravitational pull of the sun and
planets.
The Earth runs into this trail every June and November. According
to Prof
Napier these encounters have had dramatic consequences. He said:
"There is
evidence that dust from this comet may have played a role in the
last Ice
Age, and also caused climatic change during the Dark Ages."
A comparison of dust found in ice cores from these periods could
help to
confirm such theories.
© Copyright of Telegraph Group Limited 2002.
=============
(2) PRESTO, CHANGE-O! COSMIC IMPACT TRANSFORM EARTH'S SURFACE IN
AN INSTANT
>From Science News, 15 June 2002
http://www.sciencenews.org/20020615/bob9.asp
Extraterrestrial impacts transform Earth's surface in an instant
Sid Perkins
Most geological processes unfold at less than a snail's pace. The
tectonic
plates that cover Earth's surface slog along, crashing into and
sliding over
one another at rates of only a few millimeters per year. Over
millions of
years, however, these unhurried liaisons raise mountain ranges.
Wind, rain,
and natural chemical erosion gradually rework the mountains into
silt, clay,
and dissolved minerals. Slowly, this inorganic detritus wends its
way to the
sea, where it joins a languid rain of dead marine organisms to
form thick
layers of ocean-floor ooze.
Every now and again, however, things happen in a flash.
Asteroids, comets,
and smaller objects smack into the planet at clips of thousands
of
kilometers per hour. When this happens, the impacts can gouge
sizable holes
in Earth's outer crust. Within milliseconds, rocks at the impact
site
vaporize. The rapid expansion of this superheated gas blows
melted and
pulverized material into the atmosphere or back into space.
The immense seismic vibrations from an impact can create
temperatures high
enough to melt or demagnetize some rocks in and near the crater.
Farther
away, the sudden changes in pressure triggered by shock waves
shatter and
otherwise transform mineral crystals as no other geological
process does.
Although these planetary bruises and black eyes have
significantly shaped
the planet's surface, many have remained hidden. Scientists are
taking
advantage of the magnetic and gravitational scars of these
impacts to
identify the sites of the most dramatic bombardments this planet
has ever
experienced.
When worlds collide
Many of the smallest objects on a collision course with Earth
burn up in the
atmosphere before they reach the surface. A meteoroid-an
interplanetary
object ranging in size from a dust grain up to a mountain-needs
to be at
least the size of a child's marble to blaze all the way to
Earth's surface.
Anything that survives the fall is, by definition, a meteorite.
The kinetic
energy of the meteorite when it strikes the ground-a function of
the mass of
the space rock and its velocity-strongly influences the size of
the hole or
the splash it creates.
Tiny meteorites are slowed by the atmosphere so much that they
simply drop
to the ground, sometimes making no more than a dent. When these
dark objects
fall on frozen, snow-covered terrain, they're particularly easy
to find.
Residents of Canada's Yukon Territory recovered pieces of a rare
carbon-rich
meteorite soon after it fell in January 2000 (SN: 4/8/00, p.
235), and
scientists visiting Antarctica routinely use snowmobiles to hunt
for the
extraterrestrial rocks.
More-massive meteoroids are slowed less by air resistance and
therefore pack
a bigger punch when they land. They typically gouge out classic,
bowl-shaped
craters. Arizona's Meteor Crater-also known as Barringer Crater,
after the
Philadelphia mining engineer who began studying the site in
1902-is the
best-preserved terrestrial example of such a so-called simple
crater.
The impact scar, located about 20 kilometers west of Winslow,
Ariz., was
formed nearly 50,000 years ago when an iron-nickel meteorite
about 45 meters
in diameter punched through the region's rocky plain. The impact
energy of
20 million tons of TNT was roughly equivalent to the power of a
hydrogen
bomb. The sudden collision vaporized the meteorite, pulverized
rocks at
ground zero, and heaved large blocks of limestone, some the size
of small
homes, out of a 200-m deep, 1.2-km-diameter hole. That debris
formed an
elevated rim that still rises above the Arizona plain.
On Earth, craters that range up to about 5 km across have this
simple
structure, says Harrison H. Schmitt, a geologist and retired
astronaut who
trained at Meteor Crater before walking on the moon during the
Apollo 17
mission.
Meteoroids larger than 200 m or so across create a different type
of impact
scar when they slam into Earth, says Thomas Kenkmann, a geologist
at
Humboldt University in Berlin. These complex craters have a flat
floor
marked with a central uplift, which typically is either a single
or ring
peak. This uplift forms as the rocks beneath the deepest portion
of the
crater floor rebound from the compressive shock of the
meteorite's impact.
Complex craters also have terraced rims, which form when the
initially steep
walls of the crater collapse downward and inward. An analysis of
twisted
rocks taken from the central uplift of the 7-km-wide Crooked
Creek crater in
Missouri suggests that this collapse is very quick, says
Kenkmann.
The roughly 320-million-year-old impact occurred in sediments
composed of
mineral grains 10 to 100 micrometers in diameter bound into rock.
As many as
40 percent of the boundaries between individual grains were
fractured, and
rock deformation typically took place in bands between 10 and 500
micrometers wide. None of the grains seem to have been stretched
before they
broke. All these clues point to the crater collapsing in less
than 30
seconds, says Kenkmann. His analyses of several complex craters
between 5
and 15 km in diameter suggest that their rims collapsed within a
minute of
the impact. He reports his findings in the March Geology.
The pressure's off
Thick sheets of melted rocks line the bottom of many large meteor
craters.
Some of these impact melts derive from the kinetic energy of the
impact, a
large part of which is converted to heat when the meteorite
smacks Earth and
grinds to an abrupt stop. However, the sudden excavation of a
large crater
probably plays a bigger role in forming impact melts, says
Schmitt.
Rocks lying kilometers deep within Earth are often on the verge
of melting
but are prevented from doing so by the immense pressure of all
the material
above them. When meteorites blast that weight away, the pressure
in the
rocks beneath the crater floor drops precipitously and the
underlying
minerals melt. The impact melts may not fully cool for hundreds
of thousands
of years. In the meantime, water from the environment and the
heat from the
newly exposed rocks can combine to form hydrothermal systems in
the heavily
fractured rocks in and around the crater. Scientists believe such
warm,
mineral-rich venues could have played a role in the early
development of
life on Earth (SN: 3/9/02, p. 147: Available to subscribers at
http://www.sciencenews.org/20020309/fob2.asp).
The 200-m-thick impact melts found within an ancient crater
surrounding the
town of Sudbury in central Ontario are more than a sign of
extraterrestrial
impact: They're a treasure trove of minerals. More than $1
billion of metal
ores including those bearing nickel, platinum, and copper are
mined from the
melts each year, says Richard Grieve, a geologist at Natural
Resources
Canada in Ottawa. Isotopic analyses show that the metals come
from Earth's
crust, not from the meteor that fell from space. Before the
impact melts
solidified, the deep, thick blend of light silicates and dense
metal
ores-which didn't mix well with each other-separated into two
layers,
according to density, just like oil and vinegar do. This ancient
segregation
makes mining today much easier.
The hydrothermal system created by the Sudbury impact also
dissolved
minerals containing copper and other metals from a broad area and
then
concentrated them in rich veins. One large outcrop of ore alone
holds
minerals valued around $100 billion, says Grieve. The economic
interest in
the area has proven a boon to scientists, who have attained
access to deep
rock cores originally extracted to determine the best locations
to sink
mining shafts.
Radioactive dating of the melts and the hydrothermal deposits
indicates the
Sudbury impact occurred about 1.85 billion years ago. The
original crater
probably was between 250 and 300 km across, says Grieve. It's
tough to tell
because erosion, including the ravages of several ice ages, has
scraped away
up to 4 km of Earth's surface from the crater site. That has
erased many of
the impact's effects.
A somewhat older impact crater provides a deeper view. The
Vredefort impact
structure, named after the city in South Africa that was built in
the center
of the ancient bull's-eye, was created by a collision about 2.02
billion
years ago. The rocks now at Earth's surface there were once
between 7 and 10
km belowground, says Roger Gibson of the University of the
Witwatersrand in
Johannesburg. That much overlying material, including all of the
crater's
impact melts, has eroded away since the crater formed. However,
that loss is
science's gain: The erosion has made it easy for geologists to
get samples
of rock that formed deep within the crater's central peak, now a
dome of
exposed material.
Most of the crystalline mineral grains in the dome's rocks
measure between 1
and 5 millimeters across, which matches the grain size for
similar rocks in
the area. However, rocks found within 5 km of the center of the
Vredefort
dome typically have grains no more than 100 micrometers across.
Because
grain size is related to the length of time that the crystal took
to grow,
Gibson contends that the rocks in the center of the dome
experienced a short
burst of terrific heat before they rebounded toward Earth's
surface.
His analyses indicate that the rocks were between 15 and 20 km
below ground,
at around 400°C, before the impact occurred. Then, during the
strike from
space, temperatures in the rocks directly beneath the impact
briefly rose to
between 1,000°C and 1,400°C, primarily due to intense shock
waves. At sites
about 25 km from the impact, shock waves had dissipated somewhat,
and the
rocky material there got only a small boost in temperature,
Gibson says. His
team's analyses appear in the May Geology.
New finds, old tools
Extraterrestrial impacts leave distinct calling cards. For
instance, when a
rock's temperature rises above its so-called blocking
temperature, any
magnetic fields in the minerals are disrupted and then realign to
match the
strength and direction of the magnetic fields in the rock's
environment.
This phenomenon takes place in molten rocks spewing from
volcanoes and
undersea ridges, but it also takes place in the wake of meteor
strikes. If
the magnetic field at the location of an extraterrestrial impact
is
significantly different from the one in place when those rocks
last cooled,
then the cosmic bruise will produce magnetic anomalies.
Those irregularities can be quite extensive, says Jasper Halekas,
a
geophysicist at the University of California, Berkeley. He and
his
colleagues have analyzed data collected from lunar craters during
the Apollo
moon missions and the more recent Lunar Prospector probe. Those
studies show
magnetic anomalies that often extend up to several crater radii
from an
impact site. That finding implicates temperature boosts from
seismic shock
rather than exposure to vaporized material from the meteorite.
The team
presented its results last December at a meeting of the American
Geophysical
Union in San Francisco.
Impacts also can produce gravitational anomalies. Even long after
an impact
scar becomes heavily eroded, the pulverized rock that fills the
crater
bottom is much less dense than the solid rock from which it's
derived. The
precise force of gravity at any location depends, in part, on the
density
and amount of material in the neighborhood. Impact melts and a
central
uplift, if any, also can affect local gravitational patterns.
Other geological processes can produce magnetic and gravitational
anomalies,
but when these two hallmarks occur together, or are backed up
with other
geologic evidence, it's a strong hint that scientists may have
found an
ancient impact site. At the meeting in San Francisco, Dallas
Abbott and her
colleagues at Lamont-Doherty Earth Observatory in Palisades,
N.Y., described
a possible impact crater southeast of Hawaii. They found two
strong magnetic
anomalies, possibly related to impact melts, inside an unusually
shallow,
150-km-diameter crater that lies in water about 3.8 km deep.
The team also found small spherules of glassy material in
sediments all
around the proposed impact site. The tiny orbs ranged up to 200
micrometers
in diameter, a size characteristic of those produced by
meteorites that
create craters 55 km or more across. The crater may be
uncharacteristically
shallow for a couple of reasons, the researchers say. First, the
deep water
probably cushioned the blow of the meteorite. Also, chemical
analyses of the
spherules, which are high in potassium and low in silicon,
suggest that the
impact landed on an undersea mountain rather than flat ocean
floor.
A group of scientists from the University of South Carolina in
Columbia says
that they've used geological anomalies, as well as clues from
rock samples,
to identify an ancient crater buried beneath the piedmont
sediments of their
state. A magnetic anomaly about 10 km across is nearly
superimposed on a
12-km-diameter gravitational irregularity near the town of
Johnsonville,
says geologist Christopher D. Parkinson. A 290-m borehole,
drilled when
other scientists were studying the area's aquifers, shows that
sediments at
the proposed impact site are about 275 m thick. The deepest
sediments were
laid down about 90 million years ago, and they lie directly on
top of
basement rock that is a little less than 300 million years old.
Shocked quartz and other metamorphic changes in the basement
rocks indicate
the minerals were subjected to the intense pressures and strong
seismic
waves generated by a meteorite impact, says Parkinson. Some of
the changes
suggest that temperatures in the rocks rose to at least 1,300°C.
Other boreholes drilled in the area during the aquifer study were
spaced 20
to 50 km apart and, like the Johnsonville borehole, extended all
the way to
the basement rocks. All these other sediment cores include a
layer of
volcanic basalt, dozens of meters thick, that was laid down about
200
million years ago.
Parkinson suggests that the Johnsonville core doesn't contain
this basalt
because it was blown away by an impact that occurred between 90
million and
200 million years ago. The team is now conducting detailed
analyses of the
melt glasses in the sediments, which should provide a more
specific date for
one of the Piedmont's worst days in the last few thousand
millennia.
So far, scientists have identified fewer than 200 impact craters
on our
planet. However, one look at the pockmarked moon-which shares
Earth's orbit
around the sun-suggests that many of our planet's scars have
faded or remain
hidden. Finding ancient craters and unveiling their geophysical
histories
will help fill in the blanks of Earth's continuing story.
References:
Abbott, D.H., et al. 2001. Ewing structure: A possible abyssal
impact crater
(Abstract P22D-04). American Geophysical Union Fall Meeting.
December 10-14.
San Francisco.
Gibson, R.L., et al. 2002. Metamorphism on the moon: A
terrestrial analogue
in the Vredefort dome, South Africa? Geology 30(May):475-478.
Abstract
Grieve, R., and A. Therriault. 2000. Vredefort, Sudbury,
Chicxulub: Three of
a kind? Annual Review of Earth and Planetary Science 28:305.
Halekas, J.S., et al. 2001. The role of shock in lunar
paleomagnetism
(Abstract GP32A-0191). American Geophysical Union Fall Meeting.
December
10-14. San Francisco.
Kenkmann, T. 2002. Folding within seconds. Geology
30(March):231-234.
Abstract
Parkinson, C.D., P. Talwani, and E. Wildermuth. 2002. The
Johnsonville
Impact Crater, South Carolina: Petrologic evidence of shock
metamorphism
from core samples (Abstract T21A-10). American Geophysical Union
Spring
Meeting. May 28-31. Washington, D.C.
Wildermuth, E., P. Talwani, and C.D. Parkinson. 2002. Potential
field
analysis of the Johnsonville Impact Crater, South Carolina.
Presentation
T21A-09 at American Geophysical Union Spring Meeting. May 28-31.
Washington,
D.C.
Further Readings:
Cowen, R. 2000. Rocks on the ice. Science News 157(April 8):235.
__. 2001. A meteorite's pristine origins. Science News 160(Sept.
29):203.
Available to subscribers at http://www.sciencenews.org/20010929/note12.asp.
Perkins, S. 2002. Space Rocks' Demo Job: Asteroids, not comets,
pummelled
early Earth. Science News 161(March 9):147. Available to
subscribers at
http://www.sciencenews.org/20020309/fob2.asp.
__. 2002. Mangled microfossils may mark impact sites. Science
News 161(June
15):382. Available to subscribers at
http://www.sciencenews.org/20020615/note14.asp.
Copyright ©2002 Science Service. All rights reserved.
=============
(3) IMPACT CRATERING: BRIDGING THE GAP BETWEEN MODELING AND
OBSERVATIONS
>From Ron Baalke <baalke@jpl.nasa.gov>
http://www.lpi.usra.edu/meetings/impact2003/impact2003.1st.html
IMPACT CRATERING: BRIDGING THE GAP BETWEEN MODELING AND
OBSERVATIONS
Houston, Texas
February 7-9, 2003
First Announcement
June 2002
Sponsored By
Lunar and Planetary Institute
Conveners
Robert Herrick, Lunar and Planetary Institute
Elisabetta Pierazzo, Planetary Science Institute
Scientific Organizing Committee
Bevan French, Natural History Museum
Keven Housen, Boeing Corporation
William McKinnon, Washington University
Michael Zolensky, NASA Johnson Space Center
SCOPE AND PURPOSE
This workshop will address how physical observations of craters,
both on
Earth and on other solid bodies of the solar system, can be
combined with
the results from modeling of impact cratering for a better
understanding of
the impact cratering process.
The main goals of the workshop are to reconcile physical
observations with
theoretical and experimental modeling of impact processes, and to
point out
areas that future studies should focus on to improve the
observation/modeling connection.
A technical report that includes workshop overviews and a
synopsis of the
results of the meeting will be produced and distributed in
electronic
format. Authors will be allowed to submit revised versions of
their
abstracts during a limited time period. Another potential product
of the
workshop is the production of a journal special issue with
invited synthesis
papers and additional submitted papers.
ALL ABSTRACT SUBMISSIONS MUST DISCUSS BOTH MODELING AND
OBSERVATIONS, either
in the context of observations necessary to evaluate impact
models or how
particular observations constrain the impact process.
TENTATIVE WORKSHOP SCHEDULE
The morning sessions will run from 8:30 a.m. until 12:15 p.m.,
and afternoon
sessions will run from 1:30 until 5:15 p.m.
The opening session will include two 45-minute opening
presentations (35-40
minutes plus questions), one by a prominent model-oriented
scientist and the
other by an observation-oriented scientist, under the broad topic
of "What I
Hope to Get Out of this Workshop."
A 4-hour session on "Rock Properties that Need to be Known
for Theoretical
Modeling" will follow the opening session and will have two
30-minute
invited talks introducing the topic. A panel-led discussion will
follow on
samples that need to be taken in the field, sample analyses that
need to be
done, and what geologists should be looking for in the field.
The five remaining workshop sessions will include the topics
below. There
are obviously more potential topic possibilities than available
sessions, so
some combining of topics will be necessary. This list is subject
to change
based on submissions and input from attendees.
* Thermodynamics of impact cratering: shock-wave
passage,
melt/vapor production, post-impact
thermal state.
* Can the mass and composition of the impactor
really be
determined for a terrestrial crater?
* How is the structure of a complex crater created?
* Oblique impact effects, and ejecta emplacement.
Can the
direction of impact really be determined
for a
terrestrial crater?
* The effects of target properties on the cratering
process. Topic includes target layering
and target
composition.
For each of these sessions we envision two invited talks of 30
minutes, one
by a modeler and one by an observationalist, with the remainder
of the talks
as contributions. Each invited talk will be followed by 10
minutes for
discussion, and a 30-40 minute general discussion session at the
end of each
session.
A two-hour poster session is scheduled for the evening of the
first day, but
posters will remain on display throughout the entire meeting.
The workshop will be closed by a three-hour wrap-up session
consisting of a
panel-moderated discussion.
TRAVEL ASSISTANCE
Some funds will be allocated to provide travel assistance to
invited
speakers, students and recent PhDs.
INDICATION OF INTEREST
To subscribe to a mailing list to receive electronic reminders or
special
announcements relating to the meeting via e-mail, please submit
the
Electronic Indication of Interest form by July 31, 2002. This
will also
serve to facilitate meeting planning by the conveners.
CONTACTS
Robert
Herrick
Elisabetta Pierazzo
Lunar and Planetary Institute
Planetary Science Institute
e-mail: herrick@lpi.usra.edu
e-mail: betty@psi.edu
SCHEDULE
July 31,
2002 Indication of
Interest forms due to LPI
September 18, 2002 Second announcement,
including call for abstracts
and preregistration form, available on Web site
November 14, 2002 Deadline for
electronic submission of abstracts
December 18, 2002 Final
announcement, preliminary program, and
abstracts available on Web site
January 23, 2003
Preregistration deadline
February 7-9, 2003 Workshop held at LPI
===========
(4) JAPAN INVITES THE MASSES TO LAND ON ASTEROID
>From CNN, 14 June 2002
http://www.cnn.com/2002/TECH/space/06/14/japan.asteroid/index.html
By Richard Stenger
CNN
(CNN) -- Want to land on an asteroid with a legion of fellow
explorers? You
can, thanks to a Japanese space mission that launches later this
year. But
the achievement will be in name only.
The Muses-C spacecraft, the first designed to visit a space rock
and return
to Earth with geological samples, is slated to depart in November
or
December.
The Planetary Society of Japan hopes that at least a million
names from all
over the world will go along for the ride. The group of space
enthusiasts
recently kicked off a campaign to collect names and will continue
to do so
until July 6.
"The mission to return a sample of the asteroid to Earth is
a bold and
scientifically valuable undertaking," said Louis
Friedman, executive director of the Planetary Society, in a
statement this
week. The Pasadena, California-based group maintains close ties
with the
Planetary Society of Japan.
The names will be etched on an aluminum foil sheet inside a
softball-sized
ball that will accompany the probe. The sphere, a target marker,
will help
the robot ship land when it reaches asteroid 1998 SF36 in 2005.
It will be dropped onto the asteroid, where it will serve as a
navigation
landmark for the descending craft, according to the Planetary
Society.
Asteroid 1998 SF36 orbits the sun about once every 1.5 years and
is about
2,300-by-1,000 feet (700-by-300 meters). It is on average about
84 million
miles (134 million km) from Earth, but can swing as close as 1.3
million
miles (2.1 million km) or closer, according to scientists.
The space rock is considerably smaller than the asteroid Eros,
which a NASA
probe touched down on in February 2001. The NEAR-Shoemaker had
nearly
exhausted its power supply after orbiting and studying the
Manhattan-sized
space rock for a year.
Mission engineers guided the craft to the impromptu landing to
squeeze as
much scientific data from the mission as possible.
But Muses-C is designed to return home. After scooping up several
asteroid
samples, it should head back in our direction and send its cargo
to Earth in
a capsule that parachutes down to Australia in 2007.
The Planetary Society of Japan has more details about the
asteroid campaign
at the following English-language site:
http://www.planetary.or.jp/muses-c/pc/en/
Copyright 2002, CNN
==========
(5) SCIENTISTS GATHER THIS FALL TO STUDY PREVENTING AN ASTEROID
STRIKE ON
EARTH
>From Pittsburgh Post-Gazette, 17 June 2002
http://www.post-gazette.com/healthscience/20020617asteroids0617p2.asp
Monday, June 17, 2002
By Michael Woods, Post-Gazette National Bureau
The federal government is summoning the world's top scientists to
plan
defenses against an attack that could wipe out an American city
or disrupt
the whole country's infrastructure.
No, it's not global terrorism.
The scientists will map ways to combat an asteroid impact like
the collision
that killed the dinosaurs 65 million years ago and flattened a
Siberian
forest in 1908.
While the world's attention is focused on the real threat of
terrorism, the
theoretical asteroid menace has been garnering behind-the-scenes
attention.
It was the topic for an international meeting hosted by Britain's
Royal
Astronomical Society in December. In March, NASA activated
Sentry, an
automated system to monitor near-Earth asteroids and assess their
threat.
And NASA will gather scientists in September in Washington, D.C.,
to talk
about how an incoming asteroid might be deflected and what sort
of research
would be required to design and build a system to do that.
"We've had a couple of close shaves during the past few
months," said Brian
G. Marsden, with the Harvard-Smithsonian Center for Astrophysics
in
Cambridge, Mass.
One asteroid caused jitters when discovered March 12. Named 2002
EM7, it
came from the direction of the sun but was hidden by the sun's
glare.
Astronomers didn't detect 2002 EM7 until four days after it came
within
288,000 miles of Earth, which they regarded as a close encounter.
The asteroid was about 200 feet in diameter -- big enough to fill
two-thirds
of a football field -- and could have flattened a city,
unleashing the
energy of a 5-megaton nuclear bomb.
"I think Mother Nature has given us yet another wake-up
call," said Donald
K. Yeomans, manager of NASA's Near-Earth Object Program Office.
"Objects the
size of 2002 EM7 pass as close as this one did every two weeks or
so. We
just haven't found them all yet."
A similar scare occurred in January, when a 1,000-foot-diameter
asteroid
came within 375,000 miles of Earth. Astronomers had detected the
mountain-sized rock, named 2001 YB5, only a few weeks earlier.
We can expect more close-encounter stories.
"It is simply a matter of our increasing prowess in
detection that objects
like 2001 YB5 are now being seen," said Richard P. Binzel of
the
Massachusetts Institute of Technology.
NASA, the European Space Agency, and universities have been
tracking
near-Earth objects with great precision.
"The goal is to track NEOs well in advance of any
Earth-threatening
encounters so that a mitigation plan could be put into
effect," said
Yeomans, with NASA's Jet Propulsion Laboratory in Pasadena,
Calif. "No
objects that we know about threaten us, and we're well on the way
to finding
the majority of the entire population of large NEOs."
Finding the smaller ones, like 2002 EM7, will take years longer
and require
bigger telescopes than those used in asteroid search-and-tracking
efforts.
"That said, NEOs are not something to lose sleep over,"
Yeomans added.
Gareth Williams, of the Smithsonian center, cited the importance
of
detecting small asteroids when they're visible -- not hidden in
the sun's
glare -- so they can be tracked and monitored.
Objects the size of 2002 EM7 make similarly close approaches to
Earth
several times a month, Williams said. They hit Earth every 30 to
100 years,
but usually burn up in the atmosphere.
Such impacts, however, create an air burst, or powerful shock
wave, that can
cause great damage on the ground.
"The 1908 Tunguska event was an example of the local damage
that would occur
under and around the air burst of such an object," Williams
explained. In
that incident near the Stony Tunguska River in Siberia, a
mysterious air
explosion -- now believed to be an asteroid impact -- leveled a
section of
forest half the size of Rhode Island. Scientists estimate it
caused as much
destruction as a 15-megaton nuclear bomb.
"Impacts by such objects are not likely to cause major loss
of human life,"
Williams said. "About 70 percent of the world's surface is
water, and much
of the land mass is either uninhabited or very sparsely
populated."
Using the 1,000-foot diameter 2000 YB5 asteroid as an
illustration, Binzel
said there is about a 1-in-10,000 chance of an impact with Earth
each year
or a 1-in-100 chance of an impact sometime during the 21st
century.
Binzel said 2001 YB5 and 2002 EM7 were essentially no-risk
asteroids.
"Most of these chances are in the 1-in-a-million or
1-in-a-billion range,"
Marsden said. "And it is very likely that that, as we make
further
observations, the impact probabilities will become precisely
zero."
The only nightmare near-Earth object known today is 2002 CU11,
which is
about 2,000 feet in diameter and has a 1-in-9,000 chance of
hitting Earth on
Aug. 31, 2049. It was discovered in February. Scientists think
there are at
least eight other Earth-impact possibilities between 2032 and
2096.
NASA described its September conference as "urgent"
because scientists
believe it will take 70 years to develop mitigation technology
and learn to
use it against an Earth-threatening object.
"The more we know about NEOs, and the longer the advance
notice of possible
impacts, the better off we are," said Marsden. "We can
do it," he added.
"Pity the poor dinosaurs, who couldn't."
Copyright ©1997-2002 PG Publishing Co., Inc. All Rights
Reserved.
=============
(6) GOOD NEWS FOR PLANETARY DEFENSE: ANTI-MISSILE TECHNOLOGY
IMPROVING
STEADILY
>From BBC News Online, 14 June 2002
http://news.bbc.co.uk/hi/english/world/americas/newsid_2044000/2044289.stm
The United States has successfully destroyed a missile in space
with a
rocket fired from a Navy ship, hours after a treaty with Russia
ending a ban
on missile defence systems came into effect.
Pentagon officials said the exercise showed an incoming missile
could be
intercepted by a rocket guided by a warship's radar.
The test gave an important boost to President George W Bush's
plans to build
a protective shield against a foreign missile attack.
Earlier, Mr Bush vowed to speed up work on missile defence to
protect
America from what he called terrorists and rogue states.
Direct hit
In the latest test, an Aries dummy missile was fired from a site
in Hawaii,
and an interceptor rocket was launched from the USS Erie, in the
Pacific.
The interceptor was guided by a warship radar
The ship's radar tracked the dummy missile and guided the rocket
to
intercept it more than 100 miles (161 kilometres) above the
ocean.
Military officials said the test would not have violated the 1972
ABM Treaty
with Moscow because it was conducted under controlled conditions
and did not
prove whether a real intercontinental missile could be brought
down.
The results would, however, be useful in developing a missile
defence
system, they said.
Treaty obsolete
Hours earlier, the United States officially withdrew from the
1972 treaty.
That treaty served as the cornerstone of US-Soviet nuclear
deterrence by
eliminating the incentive to attack the other side because of the
threat of
massive retaliation without protection.
In a statement marking America's withdrawal from the treaty,
President Bush
said modern-day threats created a need for a national defense
system.
"As the events of 11 September made clear, we no longer live
in the Cold War
world for which the ABM Treaty was designed.
"We now face new threats from terrorists who seek to destroy
our
civilisation by any means available to rogue states armed with
weapons of
mass destruction and long-range missiles," he said.
Defence plans
Mr Bush said he was "committed to deploying a missile
defence system as soon
as possible to protect the American people".
Plans for a missile defence system have been criticised by
opponents for
being too expensive and unreliable.
But with five successful missile tests in a row, the Pentagon is
determined
to push ahead with its plans.
Work will begin next weekend on construction of six underground
silos for
missile interceptors, prohibited while the ABM Treaty was in
force.
Military officials say a rudimentary missile defence system
should be in
place over Alaska by the year 2004.
Copyright 2002, BBC
============================
* LETTERS TO THE MODERATOR *
============================
(7) MISCELLANEOUS ITEMS AND COMMENT ON CONTOUR
>From E.P. Grondine <epgrondine@hotmail.com>
Hello Benny -
A number of minor items have recently passed over my desk, none
worthy of a
full piece, but none the less interesting enough to share
with Conference
participants in some detail. This being the case, I have
combined these
items with a few small observations on the CONTOUR spacecraft; a
number of
Conference participants are either working directly on CONTOUR,
or will be
working indirectly with its data, and are far more expert on the
craft than
I am.
A FASCINATING QUESTION
I recently recieved a request for help from W.E. Lamb, a student
at NYU in
New York, who wanted to know "How many large impact craters
are observable
on Earth?".
Note that Lamb did not ask "How many large impact craters
have been observed
on Earth?", an answer to which may be found at the Canadian
Geological
Services interent site http://gdcinfo.agg.emr.ca/crater/index_e.html
(and a
shot of Eisner with a tip of the O'keefe's to them).
No, Lamb asked how many large craters are OBSERVABLE, not how
many large
craters had been OBSERVED. Conference participants are
familiar with both
the current estimates as to the total population of near Earth
asteroids,
estimates which are based on the discovey rates to date, and with
the
estimates as to completeness of the search for the larger of
these, those
say of 1 kilometer diameter and greater. What Lamb's question
amounted to
was a request for similar estimates to be made for work in an
entirely
different field, that of geology, as to the rates of discovery of
an
entirely different class of data, that of large craters.
To my knowledge, no one has ever examined in detail the data on
large crater
discovery rates and formed such an estimate. Using crude linear
mathematical
techniques I estimated that around 186 large impact craters would
ultimately
be observed by the year 2012 or so, versus the roughly 150 large
craters
which have been observed to date. It seems to me that this
question really
deserves detailed consideration by those specializing in this
field.
AN UNDERUTILIZED RESOURCE
As Conference participants are aware, the recent failure of the
Rio Cuarto
features as impact structures have left at least Masse and myself
looking
for the actual site of an impact which features in a number of
Native
American people's myths. The dimensions of the area which
needs to be
searched are staggering, and given the pauncity of remains in the
case of
cometary impact, the difficulties presented in trying to find
that evidence
are great.
Pondering this problem, I recalled that some work had been done
on pollen in
sediment cores. The extent of my knowledge of this work was
that sediment
core series had been done in the Aegean in the 1970's, and that
Floyd McCoy
had recently been working on a series of cores from off the coast
of Israel.
Inquiring of Dr. McCoy, I was suprised to learn that literally
thousands of
sediment cores have been obtained world wide, including large
numbers of
sediment cores taken off the coasts of South America and Central
America.
Evidence of the burn layer for the 25 October, 2360 BCE impact
which the
Maya reported should show up in these sediment cores; further,
since the
cores are keyed to river outflows, they may enable further
localization of
the impact and thus of the Mayan term "Matawil".
Also, evidence for the ca
1150 BCE Central American mega-tsunami should also appear in
these cores:
http://chht-ntsrv.er.usgs.gov/warmclimates/products/gmexcore.html
To my knowledge, while ice cores and tree rings are currently
under study
with relation to impact events, very few people working with
these sediment
cores have been using them to look for impacts. I expect
that the anomalies
which the researchers are currently finding in their data will
lead more of
them to show up here shortly.
MORE U.S. SCIENCE FUNDING
Acting on his own and a number of his colleagues' concerns,
Congressman
Sherwood Boehlert has been organizing the legislative effort to
dramatically
increase funding for the US National Science Foundation.
Conference
participants should find most encouraging Boehlert's specific
mention of
telescopes in his statement introducing the legislation, as well
as the
legislation's specific language setting up a joint NSF-NASA
advisory
committee on astronomical research. This legislation should
do much to end
the current confusion between the two agencies, my recent reports
of which
are available in the Conference archives.
Even more encouraging, the bill sets up a specific process for
determining
national science priorities, something which has been entirely
lacking so
far; further, it sets up a method for public comment on these
priorities. I
may be biased, but my view is that there is nothing that could
have a higher
priority than finding the next 300 meter continent killer before
it hits and
kills tens of millions of people in an instant, and that thus the
LSST
should do well under this new priority evaluation process.
OBSERVATIONS ON THE CONTOUR PROGRAM
I attended the CONTOUR briefing earlier this week, and I must say
that the
CONTOUR team has designed one tough little bullet of a
spacecraft. The craft
is so rugged and simple that the team expects to put it in
"hibernation"
mode for much of its journeys to both comets Enke and W-S 3.
This ability to "hibernate" probably also explains much
of the teams'
success in moving its project forward: the craft will make no
demands on the
antennas of the Deep Space Network while they are being used for
control of
the upcoming Mars rovers, and thus it can be operated
simultaneously with
them. Researchers should note that this may be a key to having
your research
spacecraft approved: make sure that it operates alongside NASA's
future Mars
craft and that its operation in no way conflicts with them, as
these are
NASA's highest priority.
The resolution for CONTOUR will be 4 meters for Enke and 10
meters for W-S
3, the later reflecting the greater fly-by distance allocated to
the still
active comet. The resolutions will be great enough to measure the
effects of
gravitational differentiation in these comets, a key to
understanding their
formation and evolution with time. Given the extremely high
fly-by speeds,
it may safely be infered that the CCDs and spectrographs of
CONTOUR operate
with extreme rapidity, and that even following the loss of either
gyroscopes
or attitude control rockets CONTOUR would still be able to return
data of
very high quality. I don't expect either of these failures to
happen, but
then bugs in spacecraft always have a way of suddenly appearing
and then
biting you in the fanny.
At the briefing I was also given a date of 10 December for the
one pass
attempt to communicate with the NEAR spacecraft now lying on the
surface of
the asteroid Eros. The collision speed of NEAR with Eros was 5
miles per
hour, and as this force was far less than the forces which the
NEAR
spacecraft experienced and survived in its vibration tests before
launch,
one can be reasonably hopeful for the team's success in this
effort. I wish
them the best of luck.
Well, Benny that's it for now. As usual, with the greatest of
appreciation
for your efforts -
EP
=============
(8) AND FINALLY: DOOMSDAY ASTROLOGERS GET IT WRONG - FOR NOW
>From The Daily Telegraph, 8 June 2002
http://www.telegraph.co.uk/news/main.jhtml?xml=%2Fnews%2F2002%2F06%2F08%2Fwkash308.xml
Stargazers foresee conflict next week
By Rahul Bedi in New Delhi
Indian astrologers are predicting a military conflict with
Pakistan next
week, when their celestial calendars forecast the heavens to be
in "chaotic
ferment" for two days.
They say the period between 11.13 pm on June 13 and 11.18 pm on
June 15 has
a "turbulent" combination of planets presiding over the
two countries.
Delhi's leading astrologer, Acharya Govind, interprets this to
indicate that
a "skirmish" or "limited conflict" is
imminent between the nuclear rivals.
He said the Moon, clashing with the "lethal"
combination of the Sun,
Mercury, Saturn and Rahu (Dragon's Head) made this a "highly
vulnerable and
negative period" for both countries.
But nothing in the planetary configuration indicated a nuclear
exchange, Mr
Govind added.
"India may face border conflict with Pakistan," Suman
Pandit, another Delhi
astrologer predicted. The situation requires "heightened
vigil" by the army
along the border, she added.
The news added to Indians' nervousness as most are firm believers
in
astrology. There are few Indian politicians who do not have
astrologers,
palmists, numerologists or occultists on their payroll,
dominating every
public and private move.
Copyright 2002, The Daily Telegraph
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