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

    The Sunday Telegraph, 16 June 2002

    Science News, 15 June 2002

    Ron Baalke <>

    CNN, 14 June 2002

    Pittsburgh Post-Gazette, 17 June 2002

    BBC News Online, 14 June 2002

    E.P. Grondine <>

    The Daily Telegraph, 8 June 2002


>From The Sunday Telegraph, 16 June 2002
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

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.


>From Science News, 15 June 2002

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

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

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

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 400C, before the impact occurred. Then, during the strike from
space, temperatures in the rocks directly beneath the impact briefly rose to
between 1,000C and 1,400C, 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 1,300C.

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.


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.

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,

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

Perkins, S. 2002. Space Rocks' Demo Job: Asteroids, not comets, pummelled
early Earth. Science News 161(March 9):147. Available to subscribers at

__. 2002. Mangled microfossils may mark impact sites. Science News 161(June
15):382. Available to subscribers at

Copyright 2002 Science Service. All rights reserved.


>From Ron Baalke <>


Houston, Texas
February 7-9, 2003

First Announcement
June 2002

Sponsored By
Lunar and Planetary Institute

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

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.

in the context of observations necessary to evaluate impact models or how
particular observations constrain the impact process.

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

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

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.

Some funds will be allocated to provide travel assistance to invited
speakers, students and recent PhDs.

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.


Robert Herrick                     Elisabetta Pierazzo
Lunar and Planetary Institute      Planetary Science Institute
e-mail:       e-mail:

   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

>From CNN, 14 June 2002
By Richard Stenger

(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

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:

Copyright 2002, CNN


>From Pittsburgh Post-Gazette, 17 June 2002

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. 


>From BBC News Online, 14 June 2002
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



>From E.P. Grondine <>

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.


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 (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.


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:

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.


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.


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 -



>From The Daily Telegraph, 8 June 2002

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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