PLEASE NOTE:


*

CCNet 104/2002 - 9 September 2002
---------------------------------


"One might initially think, by the way, that the expressed military
interest is only in NEOs and not other minor objects. However, you can't
sort out dangerous from safe objects without tracking them all. Searching
for NEOs sweeps up many others, anyway; witness how NEAT routinely
discovers Centaurs out past Jupiter. And, since one of the most dangerous
gaps in NEO warning has to do with unknown inbound comets, it would only be
a short leap of purpose to extend the U.S. Air Force's mandate all
the way to the Oort Cloud, halfway to the next star."
--Asteroid/Comet Conmnection, 8 September 2002


"[Clark] Chapman says that with some modification, the Torino Scale
for impact risk seems to hold up well, and he suggested it should be used
consistently in communicating with the public about new possibly-hazardous
asteroids. And, he says, astronomers should avoid references to the
Palermo Scale - whose usage figured prominently in the reports six weeks
ago about a low-probability possible impact in 2019 by asteroid 2002 NT7."
-- David L. Chandler, Sky & Telescope, 6 September 2002



(1) ASTEROID THREAT TO EARTH 'REMOTE'
    The Associated Press, 6 September 2002

(2) NEAR-EARTH OBJECTS POSE THREAT, GENERAL SAYS
    Air Force Link, 6 September 2002

(3) PETE WORDEN: "THE BILLY MITCHELL OF NEOS"
    Asteroid/Comet Connection, 8 September 2002

(4) SCIENTISTS STUDY HOW TO AVOID ASTEROID STRIKE
    Florida Today, 6 September 2002

(5) SCIENCE WORKSHOP REVEALS EVOLVING PERSPECTIVE ON ASTEROID THREAT
    Ron Baalke <baalke@jpl.nasa.gov>

(6) NEAR-EARTH OBJECT RESEARCH DEEMED VITAL
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(7) IAU, ASTRONOMERS URGED TO AVOID MENTIONING 'PALERMO SCALE' IN PUBLIC
    Sky & Telescope, 6 September 2002

(8) LARGE METEOR MAY HAVE STRUCK AUSTRALIA
    Space.com, 6 September 2002

(9) METEOR BRIGHTENS SKIES FROM COLORADO TO NEBRASKA
    The Denver Post, 8 September 2002

(10) 9/11 AND ITS PREDICTED OCCURRENCE
     Charles Cockell <csco@bas.ac.uk>

(11) AND FINALLY: ONE AP WIRE - TEN HEADLINES

=============
(1) ASTEROID THREAT TO EARTH 'REMOTE'

>From The Associated Press, 6 September 2002
http://cgi.wn.com/?action=display&article=15548007&template=worldnews/search.txt&index=recent
 
WASHINGTON (AP) - A space rock big enough to cause widespread damage and
death will hit the Earth only about once every 1,000 years, but experts say
the destruction would be so extreme that nations should develop a joint
defense against asteroids.

Participants at a NASA-sponsored conference on the hazards of comets and
asteroids smashing into Earth estimated Friday that the planet probably
would be hit about once each millennium by a space rock big enough to
release about 10 megatons of explosive energy.

Such a rock, estimated at 180 feet across, scorched through the atmosphere
over Tunguska in Siberia in 1908 and flattened trees across 800 square miles
of forest land. No crater was found and experts believe the damage came from
atmospheric shock.

Bigger space rocks, which would cause considerably more damage, would hit
the Earth even more rarely.

An object of about 1,000 feet ``would flatten everything in an area the size
of New Jersey and kill everybody there,'' said Erik Asphaug of the
University of California, Santa Cruz. The planetwide effects of such a
catastrophe are unknown, he said, but debris thrown into the atmosphere
could diminish sunlight and perhaps affect agriculture for months.

If such a rock should hit the ocean, it could trigger tsunamis, giant waves
hundreds of feet high, to roll through and destroy coastal cities.

A planet-killer asteroid, big enough to destroy whole species, would be
rarest of all. The last came 65 million years ago when a six-mile-wide rock
wiped out the dinosaurs and about 70 percent of all species.

Although scientists can estimate the odds of an impact, they can't really
pinpoint when it could happen.

``We don't know when these accidents will occur,'' said Duncan Steel of the
University of Salford in England. ``There could be one sometime in the next
100 years. We don't know.''

Asphaug, the meeting's organizer, said scientists recognized the risk to the
planet of asteroids and comets in the last few decades and only now are
beginning to shape proposals to protect the planet.

``This is the only major natural hazard which can, in principle, be made
predictable and even eliminated if we find the dangerous ones and learn how
to modify their orbits over time,'' he said.

The National Aeronautics and Space Administration, under a congressional
mandate, started an organized effort in 1998 to find and plot the orbital
paths of every Near Earth Asteroid larger than three-fifths of a mile
across. Six international observatories are scanning the skies. More than
600 such asteroids have been found, out of an expected 1,000. None
represents a threat.

Astronomers now propose a special observatory, called the Large Synoptic
Survey Telescope, that would be able to detect much smaller asteroids. It is
estimated the proposed instrument, with a 27 1/2 -foot primary mirror, would
be able to find and plot the path of space rocks down to a diameter of 820
feet.

While the search continues, experts are studying ways to prevent any object
from hitting the planet.

It is believed that most asteroids that pose catastrophic danger would be
spotted decades before they could endanger Earth. This makes it
theoretically possible to deflect the speeding space rock and send it into a
new, safer direction.

Unlike Hollywood films that have had crews blowing up such asteroids, the
most promising method of deflection would be to change the path of the
asteroid slowly, over decades, using small rockets or other devices, Asphaug
and other experts believe. Some have suggested that solar concentrators
placed precisely on an asteroid could heat and vaporize enough rocky
material to provide a thrust that would reshape the object's orbit to spare
Earth.

Before such engineering techniques can be developed, the experts said they
need to know more about the asteroids.

Most of the space objects, astronomers believe, are aggregates of rock and
dust, held together loosely by gravity. About one in six of the discovered
large asteroids have moons, which complicates any effort to change their
orbital paths. 

Copyright 2002, AP

===========
(2) NEAR-EARTH OBJECTS POSE THREAT, GENERAL SAYS

>From Air Force Link, 6 September 2002
http://www.af.mil/news/Sep2002/90602255.shtml

by Staff Sgt. A.J. Bosker
Air Force Print News

09/06/02 - WASHINGTON -- This summer, much of the world watched as India and
Pakistan faced-off over the disputed Kashmir region, worried that the
showdown could escalate into a nuclear war.

Coincidentally, U.S. early warning satellites detected an explosion in the
Earth's atmosphere June 6, at the height of the tension, with an energy
release estimated to be 12 kilotons.

Fortunately the detonation, equivalent to the blast that destroyed
Hiroshima, occurred over the Mediterranean Sea. However, if it had occurred
at the same latitude a few hours earlier, the result on human affairs might
have been much worse, said Brig. Gen. Simon P. Worden, U.S. Space Command's
deputy director for operations at Peterson Air Force Base, Colo.

Had the bright flash, accompanied by a damaging shock wave, occurred over
India or Pakistan, the resulting panic could have sparked a nuclear war,
Worden recently told members of the congressionally mandated Commission on
the Future of the U.S. Aerospace Industry in testimony here.

Although U.S. officials quickly determined that a meteor caused the
explosion, neither India nor Pakistan have the sophisticated sensors that
can determine the difference between a natural near-Earth object impact and
a nuclear detonation, Worden said in written testimony.

This is one of many threats posed by NEOs, especially as more and more
nations acquire nuclear weapons, said Worden, who appeared before the
commission as a scientist who has studied NEOs and as a space expert
familiar with the technologies that can be used to address the NEO threat.

In recent years, the Department of Defense has been working to provide data
about asteroid strikes to nations potentially under missile attack and to
the scientific community; however, it takes several weeks for the data to be
released since much of it is gathered from classified systems.

Worden suggested that a NEO warning center be established that can assess
and release this data as soon as possible to all interested parties while
ensuring sensitive data is safeguarded.

He recommended to the commission that a natural impact warning clearinghouse
could be formed by adding no more than 10 people to current U.S. Space
Command early warning centers.

This organization would catalog and provide credible warning information on
future NEO impact problems, as well as rapidly provide information on the
nature of an impact.

In order for this clearinghouse to provide accurate information, NEOs must
first be detected, cataloged and their orbits defined.

Current ground-based systems are already cataloging large kilometer-sized
objects but have a difficult time finding smaller NEOs. Most sail by the
earth unnoticed until they have passed, he said.

"Just about everyone knows of the 'dinosaur killer' asteroids," Worden said.
"These are objects, a few kilometers across, that strike on time scales of
tens of millions of years. While the prospect of such strikes grabs people's
attention and makes great catastrophe movies, too much focus on these events
has been counterproductive. We need to focus our energies on the smaller,
more immediate threats."

The smaller strikes, while not exactly commonplace, have occurred on several
occasions over the past century, with potentially devastating results, he
said.

"An object probably less than 100 meters in diameter struck Tunguska in
Siberia in 1908, releasing the energy equivalent to a 10-megaton nuclear
blast," Worden said. "In 1996, our satellite sensors detected a burst over
Greenland equal to a 100-kiloton yield. Had any of these struck over a
populated area, perhaps hundreds of thousands might have perished."

An even worse catastrophe would be an ocean impact near a heavily populated
shore by one of these Tunguska-sized objects.

"The resulting tidal wave could inundate shorelines for hundreds of miles
and potentially kill millions," Worden explained.

"There are hundreds of thousands of objects this size that come near the
Earth," he said. "We know the orbits of just a few. New space-surveillance
systems capable of scanning the entire sky every few days are needed. They
could enable us to completely catalog and warn of objects (less than 100
meters in diameter)."

According to Worden, this does not mean other groups, in particular the
international scientific community, should not continue their independent
efforts. But the United States is likely, for the foreseeable future, to
have most of the required sensors to do this job. He added that DOD has the
discipline and continuity to ensure consistent, long-term focus.

"I believe various aspects related to NEO impacts, including the possibility
that an impact would be misidentified as a nuclear attack, are critical
national and international security issues," he said. "The focus of NEO
mitigation efforts should shift to smaller objects. The near-term threats
are much more likely to come from these 'small' objects, and we might be
able to divert such objects without (resorting) to nuclear devices."

The National Defense Authorization Act for Fiscal Year 2001 established the
Commission on the Future of the U.S. Aerospace Industry. The commission was
formed to study the future of the U.S. aerospace industry in the global
economy, particularly in relationship to national security, and provide
recommendations to the president and Congress.

Copyright 2002, Air Force Link

===============
(3) PETE WORDEN: "THE BILLY MITCHELL OF NEOS"

>From Asteroid/Comet Connection, 8 September 2002
http://www.hohmanntransfer.com/news.htm

Brigadier General (and PhD astronomer) Pete Worden is beginning to look like
the "Billy Mitchell of NEOs," although apparently without Mitchell's
legendary abrasiveness. Most news reporting until now has portrayed Worden's
opinions on NEO subjects as only personal thoughts and not positions of the
U.S. Space Command, where he is a deputy director. So it is interesting to
visit the U.S. Air Force's home page at http://www.af.mil, where, in the top
right-hand "Air Force News" column, you will currently find, "Near-Earth
objects pose threat, general says"
(http://www.af.mil/news/Sep2002/90602255.shtml).

This Air Force-written story, dated 6 September, centers not on last week's
NASA hazards mitigation workshop, where Worden also participated, but on
testimony by Worden to the "congressionally mandated Commission on the
Future of the U.S. Aerospace Industry." It doesn't appear that this
testimony has been posted yet to the commission's Web site, but the general
was on the agenda for its 22 August meeting, and there is another meeting
coming up on 17 September (see the commission's reports and meetings pages).

The article says that Worden recommended to the commission that a natural
impact warning clearinghouse could be formed by adding no more than 10
people to current U.S. Space Command early warning centers. This
organization would catalog and provide credible warning information on
future NEO impact problems, as well as rapidly provide information on the
nature of an impact. In order for this clearinghouse to provide accurate
information, NEOs must first be detected, cataloged and their orbits
defined.

Such an activity would at a minimum seem to overlap, if not duplicate, the
work of the International Astronomical Union Minor Planet Center, NASA/JPL
NEO Program, and University of Pisa NEODyS program, which among themselves
have almost ten full-time employees. But, According to Worden, this does not
mean other groups, in particular the international scientific community,
should not continue their independent efforts. But the United States is
likely, for the foreseeable future, to have most of the required sensors to
do this job. He added that DOD has the discipline and continuity to ensure
consistent, long-term focus.

His clearinghouse concept is what has been getting the attention, but, to
accomplish its goals, Worden will also have to push for the ground- and
space-based military resources needed to find the "hundreds of thousands" of
NEOs of a size on the order of 100 meters/yards wide. This is well beyond
the current official NEO cataloging goals (and abilities) of the IAU,
Congress, NASA, and wider NEO community.

Involving the military wouldn't be anything new, of course. Most NEO
discoveries today are already being made from U.S. military installations
with military hardware, mainly LINEAR in New Mexico as well as the Hawaiian
telescope used by JPL's NEAT program. And most atmospheric event detections
are being made with U.S. military ground sensors, and with satellites that
were under Worden's command during 1994-96.

Will we someday be talking about military-designated minor objects? Doing
its own cataloging would allow the Space Command to publish discoveries and
orbits as "sanitized" information without having to divulge details about
the classified "technical means" used to gather the data. One can speculate
this might include giving the military a way to employ already existing
resources that have immediate potential for NEO searches but, for security
reasons, won't report data to civilian astronomers.

It does seem a stretch to imagine today's informal worldwide network of
professional and amateur astronomers all uploading their nightly
observations to Cheyenne Mountain instead of Harvard. However, if the
military doesn't take on some cataloging duties, how will the civilian
cornerstones of today's NEO monitoring deal with doublings of the number of
known minor objects? NEODyS and the JPL NEO Program currently watch NEOs
counted by hundreds. And the underfunded IAU MPC is already on overload from
keeping track of fewer than 50,000 fully cataloged comets and asteroids plus
several hundred thousand partially cataloged objects.

The future workload growth isn't coming just from possible military
surveillance, but also from new observation capabilites of many kinds. ESA's
Gaia mission, set to begin in eight years, for instance, is alone predicted
to be capable of discovering 30 to 40,000 new objects per year for five
years.

The chair of the IAU Working Group on NEOs, David Morrison, is on record
(SpaceRef.com 16 July 2002) as completely dismissing any urgency in
searching for the same objects that Worden says are actually the biggest
near-term threat and represent "critical national and international security
issues." Which brings us back to this: Who was Billy Mitchell? He was a
distinguished but controversial U.S. Army Signal Corps Brigadier General who
campaigned in the 1920s for reorganizing the U.S. military around air power.
He sank a few U.S. Navy battleships and then his own career, but his
campaign ultimately helped lead the U.S. military and aviation establishment
to be better prepared for WW-II, even if caught by surprise when the attack
on Pearl Harbor happened much like Mitchell had warned. (Here is a good
starting (http://www.airpower.maxwell.af.mil/airchronicles/cc/mitch.html)
place for learning more about Mitchell.)

One might initially think, by the way, that the expressed military interest
is only in NEOs and not other minor objects. However, you can't sort out
dangerous from safe objects without tracking them all. Searching for NEOs
sweeps up many others, anyway; witness how NEAT routinely discovers Centaurs
out past Jupiter. And, since one of the most dangerous gaps in NEO warning
has to do with unknown inbound comets, it would only be a short leap of
purpose to extend the U.S. Air Force's mandate all the way to the Oort
Cloud, halfway to the next star.

For more on these topics, see several reports archived under Planetary
defense (http://www.hohmanntransfer.com/news/0207.htm#defense), and also
Space.com's 5 August report on an outside study done for the U.S. Space
Command about setting up a clearinghouse.

Copyright 2002, Asteroid/Comet Connection

==========
(4) SCIENTISTS STUDY HOW TO AVOID ASTEROID STRIKE

>From Florida Today, 6 September 2002
http://www.floridatoday.com/!NEWSROOM/localstoryA29153A.htm

By Kelly Young
FLORIDA TODAY

CAPE CANAVERAL - Scientists in Virginia this week determined that research
being done on potentially-dangerous asteroids and comets is good, but not
enough.

If any large object veered toward Earth, the consequences could be deadly
for much of civilization. Scientists blame either a comet or asteroid impact
for wiping out the dinosaurs.

About 70 scientists and engineers met in Arlington, Va. for Tuesday through
Friday to discuss how to avoid that fate at the Workshop on Scientific
Requirements for Mitigation of Hazardous Comets and Asteroids.

After the meeting, they will draft a timeline for NASA to follow to divert
an asteroid or comet heading Earth's way.

Currently, astronomers are trying to hunt down most of the asteroids and
comets larger than six-tenths of a mile that could pose a danger to Earth in
the future.

"There's a lot of consensus we need to keep doing the surveys, the census,"
said conference attendee Dan Durda, who works for Southwest Research
Institute. "You have to know the enemy."

The good news, Durda said, is that the information that needs to be gathered
in order to put together a plan of defense for an asteroid attack is similar
to the work being done strictly for scientific purposes.

"Unlike volcanoes or earthquakes, the (Near Earth Object) hazard was only
recently identified, and we have just begun to understand its implications,"
said meeting organizer Erik Asphaug of the University of California at Santa
Cruz. "This is the only major natural hazard which can, in principle, be
made predictable and even eliminated if we find the dangerous ones and learn
how to modify their orbits over time."

More needs to be done to understand the surface and interiors of asteroids,
they said.

Recent research indicates that some asteroids might be held together
loosely, so an explosive detonated on or near it might not have the desired
effect.

Durda said that better propulsion systems must be designed.

A small but constant force applied to a space object could be enough to move
it over time. Also better engines could get to an approaching asteroid
quickly.

Durda supported human exploration of asteroids.

He said they could serve as a stepping stone to a larger mission to Mars.

Copyright 2002 FLORIDA TODAY.

=============
(5) SCIENCE WORKSHOP REVEALS EVOLVING PERSPECTIVE ON ASTEROID THREAT

>From Ron Baalke <baalke@jpl.nasa.gov>

http://www.noao.edu/outreach/press/pr02/pr0208.html

FOR IMMEDIATE RELEASE: Friday, September 6, 2002
RELEASE NO: NOAO 02-08

Science Workshop Reveals Evolving Perspective on Asteroid Threat

For More Information:

Douglas Isbell
Public Information Officer
National Optical Astronomy Observatory
Phone: 520/318-8214
E-mail: disbell@noao.edu

Prof. Erik Asphaug
University of California at Santa Cruz
Phone: 831/459-2260
E-mail: asphaug@es.ucsc.edu

Direct measurements of the surface properties and interior structures of
asteroids and comets should be fundamental elements of future spacecraft
missions to these primitive solar system bodies, according to participants
in a scientific workshop held in Arlington, VA, from September 3-6.

Such information is vitally important for preparing a variety of approaches
for the diversion of Near-Earth Objects which may someday threaten Earth.
Evidence presented at the workshop suggests that gentle thrusts applied for
decades, rather than traditional explosives, are likely to be needed to
change their orbital paths. This will require early detection together with
knowledge of their geologic properties.

Sponsored by NASA, the workshop was designed to find common ground among
researchers on the reconnaissance and exploration of Near-Earth Objects.
"Unlike volcanoes or earthquakes, the NEO hazard was only recently
identified, and we have just begun to understand its implications," said
meeting organizer Erik Asphaug of the University of California at Santa
Cruz. "This is the only major natural hazard which can, in principle, be
made predictable and even eliminated if we find the dangerous ones and learn
how to modify their orbits over time."

Astronomers have determined precise orbits and estimated the sizes of
approximately 1,500 Near-Earth Objects (NEOs), according to conference
presentations. More than 600 of the estimated 1,000 asteroids larger than
one kilometer in diameter (a size that could cause widespread calamity on
Earth) have been detected so far. This represents good progress toward the
goal mandated by Congress for NASA to discover 90% of these objects by 2008.
While no known asteroid is on collision course with Earth, ongoing detection
should alert us to serious threats.

Significant topics of discussion at the workshop included large
uncertainties in the state of scientific knowledge of asteroid surfaces,
despite great advances in recent years. There is increasing evidence that
most asteroids larger than a few hundred meters have complex interiors and
may be loosely bound conglomerates which might resist explosive diversion.
To almost everyone's surprise, about a sixth of NEOs are now observed to
have moons, which would complicate any effort to change their orbits.

While scientific goals of researching the early history of the solar system
and mitigation goals of protecting the Earth are very different, the kinds
of asteroid studies needed to address both goals are largely identical,
several participants noted. "Learning more about them is the first step,"
Asphaug said. Gathering a wide variety of measurements is critical for fully
understanding the history and properties of NEOs, given their great
diversity and their many observed dissimilarities from presumed analogues
like the surface of the Moon.

Because we know so little, physical characterization was seen by researchers
as going hand-in-hand with potentially useful technological developments.
For example, a large, lightweight solar concentrator was discussed that
could vaporize a small surface area for measurements of composition; thrust
from the escaping material could be measured to test concepts for
solar-powered asteroid deflection.

Because close-calls are far more likely than actual impacts, attendees also
discussed the deployment of radio transponders for precision tracking of
dangerous objects. Many researchers expressed the need for high-performance
propulsion systems that could power a spacecraft to a rapid rendezvous with
an NEO.

Ground-based observatories such as the proposed 8.4-meter Large Synoptic
Survey Telescope (a high priority in the most recent Decadal Survey of
astronomy by the National Academy of Sciences) can be effective tools to
detect 80-90% of the NEO population down to a diameter of 300 meters within
about a decade of full-time operations. A spacecraft orbiting close to the
Sun and looking outward in tandem with such a telescope might reduce this
time to five years. NEOs in this size range can cause widespread regional
damage on Earth, although the workshop scientists agreed that the detailed
effects of impacts of any size remain poorly understood.

Ground-based radar observations of close-approaching NEOs will also remain a
uniquely important and flexible method to study a variety of objects,
attendees agreed. Radar is capable of imaging and accurately tracking the
closest Earth-approachers.

Few countries outside of the United States are spending significant
resources on the NEO hazard, and this international imbalance must be
remedied if the threat is to be fully understood within the next few
decades, according to several speakers. For example, there are currently no
active ground-based NEO searches in the Southern Hemisphere. Despite the
spectacular success of NASA's recently concluded Near Earth Asteroid
Rendezvous mission, and excitement surrounding Japan's upcoming MUSES-C
mission (the first-ever sample return from an asteroid, to be launched in
December), researchers agreed that more substantial investigations are
required if we are to learn how to change an asteroid's orbit.

Scientists must take better advantage of opportunities to explain new
detections and their related risks to the media and the public, attendees
agreed. With advanced search systems coming on line, asteroids will be
discovered at an increasing rate, with orbits which may initially appear
dangerous. Only detailed follow-up on a case-by-case basis can prove each
new discovery to be non-threatening. This process must be communicated more
carefully, scientists agreed, in the manner that hurricanes are tracked by
the weather service until the "all-clear" is announced.

The workshop was attended by 70 scientists from the United States,
Australia, Europe and Japan. It was co-sponsored by Ball Aerospace, Science
Applications International Corp., Lockheed Martin Corp., the National
Optical Astronomy Observatory and the University of Maryland. A formal
report on the workshop will be submitted to NASA by the end of 2002.

=============
(6) NEAR-EARTH OBJECT RESEARCH DEEMED VITAL

>From Andrew Yee <ayee@nova.astro.utoronto.ca>

[ http://www.upi.com/view.cfm?StoryID=20020906-041410-9963r ]

Friday, September 6, 2002, 5:40 PM EDT

Near-Earth object research deemed vital
By SCOTT R. BURNELL, UPI Science News

ARLINGTON, Va. (UPI) -- Space agencies should devote more resources to
locating and characterizing asteroids and comets that may threaten life on
Earth, members of a scientific workshop urged Friday.

Those resources should focus on objects passing near the Sun in such fashion
that at least some portion of their paths lie within the "tube" traced by
Earth in its orbit, said Erik Asphaug, a professor at the University of
California at Santa Cruz, who organized the meeting.

The National Aeronautics and Space Administration, for example, is
attempting to discover at least 90 percent of the largest near-Earth
asteroids -- or NEOs, as they are called -- those
exceeding 1 kilometer in diameter. An Earth impact involving something that
large would have a legitimate chance of wiping out civilization, but objects
as small as a few hundred meters could pack enough punch to generate massive
tsunamis or devastate a city.

Current research, however, is discovering additional asteroid and comet
variables to consider, said Duncan Steele, an Australian astronomer now
working independently in England.

"We don't know whether we need an elephant gun or an butterfly net to deal
with them, we really are that ignorant," Steele said. "The name of the (risk
mitigation) game at this stage is 'know your enemy;' we know (these objects)
are dangerous, but just how dangerous we don't yet know."

Present theories about asteroid compositions range from solid masses of iron
to loosely bound conglomerations of rubble. Each type of asteroid therefore
would have a different impact effect and could require a unique strategy for
diverting its course.

The methods for such diversions fall well short of Hollywood's usual
solution, the nuclear bomb, the group said. Low-thrust, long-duration rocket
motors, or something as simple as a solar sail to catch the "wind" of
particles streaming out from the Sun, might be enough to do the job, given
enough advance warning.

Existing sky surveys should give decades of lead time before most potential
impacts, said Michael Belton, president of Belton Space Exploration
Initiatives in Tucson, Ariz., and an astronomer emeritus at the National
Optical Astronomy Observatories. The flip side to that good news, however,
is science needs at least another decade to come up with practical diversion
techniques, he said.

The leaders of the Workshop on Scientific Requirements for Mitigation of
Hazardous Comets and Asteroids, the formal name of the meeting, expect to
publish a recommended timeline of research necessary to meet the goal of
diverting NEOs by 2030. Some of the suggestions debated by the group include
defining an initial technology goal, such as a 2015 deadline for altering
the course of a 150-meter object by five or ten centimeters per second. That
modest change in velocity, applied soon enough, could mean the difference
between a benign near encounter and a disastrous impact.

Another idea would add capacity and redundancy to the scientific community's
ability to pick out dangerous objects from the stream of data generated by
NEO trackers and other instruments.

"The NEO hazard was only recently identified, and we have just begun to
understand its implications," Asphaug said. "This is the only major natural
hazard which can, in principle, be made predictable and even eliminated if
we find the dangerous (objects) and learn how to modify their orbits."

International cooperation in the NEO search is essential, the group said,
especially among countries in the Southern Hemisphere, where the night sky
remains largely unmonitored. Funding for such efforts need not exceed a few
million dollars per year at first, devoted primarily to additional search
resources.

If a large influx of tens or even hundreds of millions of dollars became
available, Asphaug said, it might be best spent on launching a monitoring
satellite into orbit between the Earth and the Sun, looking outward into the
solar system to spot NEOs far more effectively than ground stations.

The group also agreed the public needs much more education about the
complexities of the situation. Recent examples of advisories about possible
future collisions have been treated as firm predictions by the media, when
in reality weeks or even months of additional data are needed to determine
if the impact risk is increasing or fading away, they said.

The group started with the assumption that an object's orbit can be altered,
but that is a far cry from the science- fiction idea of "catching" asteroids
to use their raw materials, workshop members said. Gently nudging a rock
sideways for an extended period, for an end change of a few
meters per second, is several orders of magnitude easier than affecting the
Earth-object closing velocity, which can reach kilometers per second, they
said.

About 70 scientists from Australia, Europe, Japan and the United States took
part in the workshop, which was sponsored by NASA, the University of
Maryland, the National Optical Astronomy Observatories, Lockheed Martin,
Ball Aerospace and Science Applications International Corporation.

Copyright 2002 United Press International. All rights reserved.

===========
(7) IAU, ASTRONOMERS URGED TO AVOID MENTIONING 'PALERMO SCALE' IN PUBLIC

>From Sky & Telescope, 6 September 2002
http://skyandtelescope.com/news/current/article_728_1.asp

Assessing and Reporting Impact Risks

By David L. Chandler

Reports of possible impacts by comets or asteroids are not exactly a new
thing. Edmond Halley, long before the comet that bears his name made its
first predicted return, suggested that a comet might eventually strike Earth
with possibly devastating results.

It wouldn't be surprising if, back in 1690, a few press reports blew
Halley's warning way out of proportion, and astronomers worried that their
credibility would be undermined as a result. That's what regularly happens
nowadays. Faced with this problem, some of the astronomers at this
week's Workshop on Scientific Requirements for Mitigation of Hazardous
Comets and Asteroids presented ideas about how to improve public
communications surrounding the increasingly high-profile impact prediction
process.

Today's astronomers use numerical yardsticks to assess impact risk. The
Torino Scale ranks every near-Earth object on a zero-to-ten basis, with zero
representing the risk of impact being lower than that of a random unknown
object hitting Earth in the same time frame. The Torino rankings were
designed with the general public in mind, with higher values representing
both a higher probability of impact and worse damage. By contrast, the
Palermo Scale was created for astronomers' use. It assigns zero to any
object that has the same probability of hitting Earth in a given time period
that a random object would. But it also assigns negative values to objects
that pose less risk than random impacts. And its rankings are assigned
differently too, with no distinction between small impacts and big ones.

Clark Chapman (Southwest Research Institute) and Brendan Mulligan (Queen's
University, Canada) investigated a wide variety of hazard scales that have
been used to communicate everything from hurricanes and forest fires to
nuclear war and terrorism. Chapman says that with some modification, the
Torino Scale for impact risk seems to hold up well, and he suggested it
should be used consistently in communicating with the public about new
possibly-hazardous asteroids. And, he says, astronomers should avoid
references to the Palermo Scale - whose usage figured prominently in the
reports six weeks ago about a low-probability possible impact in 2019 by
asteroid 2002 NT7.

Some of those reports, Chapman says, were "confusing and inappropriate,"
since they stressed the fact that this was the first object ever to get a
positive, greater-than-zero Palermo rating. Since the scale was barely a
year old, he says, that's "like calling the Queens air crash last fall the
worst transportation disaster of the century, when the century was barely a
year old!"

David Morrison (NASA/Ames Research Center) says that on the one hand, such
reports do help raise public awareness of the issue, but they also have
"demeaned the credibility of astronomers in the public's eye." While
astronomers should not suppress information, he suggests, they should
make sure that a good, responsible report of the facts is quickly available
on the Internet, even "in a few sentences, to give our view." But he
criticizes recent suggestions for a military-run warning center for asteroid
impact predictions. Because real, substantiated warnings of a serious
asteroid danger will be so rare - perhaps one every 50 to 100 years - "this
is not a credible option," he says.

Duncan Steel (University of Salford, United Kingdom) suggested his own
analogy to help the public understand the risk and how to put it in
perspective: comparing the asteroid threat to the risk of cancer. For any
individual, the risk is low on any given day, but must be taken seriously;
early detection is crucial - if one is detected, suddenly the high cost of
mitigation becomes irrelevant. And if it is detected early enough, the
treatment can be highly effective.

Copyright 2002, Sky & Telescope

Moderator's Note:


=============
(8) LARGE METEOR MAY HAVE STRUCK AUSTRALIA

>From Space.com, 6 September 2002
http://www.space.com/scienceastronomy/meteor_australia_020906.html

By SPACE.com Staff

Residents of southern Australia reported a large fireball in the sky
Thursday night and inundated local law enforcement offices with phone calls,
according to local media reports.

An astronomer said the cause was likely a boulder-sized space rock crashing
through Earth's atmosphere and possibly hitting the planet's surface.

One witness described a whooshing sound. "It came straight over the top and
left a huge smoke trail and there was two huge sonic booms afterwards," the
person told the Australian Broadcasting Corp. (ABC). 
 
Bryan Boyle from the Anglo-Australian Telescope in New South Wales told ABC
the object probably zoomed down to at least 30 kilometers (19 miles) above
the surface. According to the Reuters news service, residents of Goolwa and
Victor Harbor, south of the state capital Adelaide, inundated police with
reports of a flash of blue light, smoke trails and two sonic booms.

"It does sound like there could well have been an impact like that on the
ground," Boyle told ABC.

Small meteors routinely enter Earth's atmosphere and burn up, creating
"shooting stars." Large objects, from basketball-size to the dimensions of a
small car, enter less frequently and typically burn up or break apart before
reaching the surface.

Asteroids the size of a bus or bigger can generate truly impressive
explosions like the one apparently witnessed yesterday. These objects,
depending on their composition, sometimes survive to the surface. Or they
can break apart and some of their pieces fall to the ground as meteorites.

Scientists hunt for meteorites and use them to learn more about asteroids
and the solar system.

There are no firm records of any human deaths by space rocks in recent
decades, but astronomers warn that the threat is real and that eventually an
asteroid will strike and cause local or regional damage and possibly deaths.

Copyright 2002, space.com

==========
(9) METEOR BRIGHTENS SKIES FROM COLORADO TO NEBRASKA

>From The Denver Post, 8 September 2002
http://www.denverpost.com/Stories/0,1413,36%257E53%257E845005%257E,00.html

By Jim Kehl
 
Sunday, September 08, 2002 - Witnesses from many parts of Colorado and
Nebraska reported seeing a long, bright fireball streaking through the sky
Friday night.

The Denver Museum of Nature and Science confirmed the fireball was a meteor,
which fell to the Earth about 8:30 p.m., according to researcher Andy
Caldwell.

Although people all over the state saw the meteor travel from roughly the
area around Steamboat Springs to Nebraska, it may not have even been over
Colorado at all.

"That's a strong misconception people often have," Caldwell said. "They see
something go behind a building and think it fell there."

Meteors fall to the Earth at anywhere from 25,000 to 45,000 mph, depending
on their angle. They become visible to ground observers when they reach
altitudes where the atmosphere becomes thicker, usually between 11 to 20
miles above the Earth's surface. Below that level, the atmosphere slows them
down, and meteorites stop glowing long before they hit the ground.

The meteor may have been as far north as Wyoming, Caldwell said.

Because of the extreme forces and temperatures meteors experience as they
travel through the atmosphere, they usually break into smaller pieces.

Some witness accounts of Friday night's fireball describe this phenomenon.

"Chances are, if any pieces of the meteorite did make it to the ground, it
would be in Nebraska or possibly even South Dakota," Caldwell said.

Over the next few weeks, researchers will sift through the many witness
accounts of the meteor, interview residents in the area who may have seen
the fireball, attempt to plot its path through the sky and possibly even
determine where the meteorite fell.

However, the chances of finding it are small.

Meteorites are usually about the size of a baseball or smaller, and after
the researchers complete their work, they will have narrowed the meteorite's
landing zone down to few square miles, according to Caldwell.

"It could have fallen on some guy's farm," Caldwell said. "He might find it
years later."

The research team is not taking phone calls, but requests that witnesses
fill out an Internet fireball report form at:
www.cloudbait.com/science/fireballs.html.

Copyright 2002, Denver Post


============================
* LETTERS TO THE MODERATOR *
============================

(10) 9/11 AND ITS PREDICTED OCCURRENCE

>From Charles Cockell <csco@bas.ac.uk>

Dear Benny,

I don't think Sir Arthur Clarke is suggesting that the Sept 11 in Rendezvous
with Rama was a strange prediction of Sept 11, but I think one has to be
careful about making connections of any kind like this. I find it very
worrisome when people (and I've read more alarming 'predictions' of Sept 11
in papers) find correlations between Sept 11 and other 'predictions'. To
find events in the past that spookily fortell or suggest something nasty was
going to happen on Sept 11 is to suggest that the events of Sept 11 were
inevitable. They were a dispicable act of terror and there was no
inevitability or pre-arranged likehood of their occurence. As they might say
in Hollywood, 'any similarity to previous events or predictions is purely
co-incidental'.

I make this point because it's also relevant to this e-mail group - when we
get finally fit by an asteroid or comet, hopefully no one will appear on
this e-mail network to say that the date of catastrophe bears some
similarity to this or that prediction. There is no inevitability of being
hit by such objects on particular days -particularly now that we are rapidly
approaching the time when we can do something about it.

Charles

Dr. Charles Cockell,
British Antarctic Survey,
High Cross,
Madingley Road,
Cambridge.
CB3 0ET. UK
Tel : + 44 1223 221560
e-mail : csco@bas.ac.uk

==========

(11) AND FINALLY: ONE AP WIRE - TEN HEADLINES

* ASTEROID THREAT TO EARTH 'REMOTE' (Newsday, 7 Sep 2002)

* ASTEROID COLLISION A THREAT (The Age (AU), 7 Sep 2002)

* ASTEROID THREAT TO EARTH REMOTE (Detroit News, 8 Sep 2002)

* NEAR-EARTH OBJECTS POSE THREAT, GENERAL SAYS (Air Force Link, 6 September 2002)

* ASTEROIDS A THREAT? GOT 1,000 YEARS? (CBS News, 7 Sep 2002)  

* EXPERTS URGE EARTHLINGS TO PREPARE FOR ASTEROID PERIL (deseretnews.com, 8 Sep 2002)

* EXPERTS FEAR ASTEROID COLLISION (indystar.com, 8 Sep 2002)

* ASTEROID EXPERTS URGE GLOBAL DEFENSE EFFORT (Tacoma Tribune, 7 Sep 2002)
 
* SCIENTISTS: TO AVERT CATACLYSMIC ASTEROIDS, DIVERT THEM
  St. Petersburg Times, 8 Sep 2002
 
* SPACE EXPERTS URGE NATIONS TO CREATE COMBINED DEFENSE AGAINST ASTEROIDS
(Miami Herald, 8 Sep)

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