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(meteorobs) Excerpts from CCNet (Some OT)



CCNet 84/2002 - 17 July  2002
-----------------------------


   "There was a great storm and hail and flashes of lightning in the
   darkened, blackened sky and a great and crashing 'thunder-noise'
   everywhere. ... There were also a great shaking, jumping and trembling
   of the earth beneath and a rolling-up of the great waters."
     --Hoh Indians from the Forks area of Washington's Olympic Peninsula 


   "Thus by my count for the 20th century we have one confirmed 60-m 
   impactor (Tunguska) and no evidence of anything else approaching this 
   size (although of course we would miss most impacts since they would 
   occur in the ocean; absence of evidence in this case is not evidence 
   of absence). For comparison, the latest estimated frequency of impact 
   of 60-meter projectiles is only about once per millennium, rather 
   lower than the older estimates of once every couple of hundred years."
         --David Morrison, 15 July 2002


(1) AN IMPACT TRIGGERED MEGA-TSUNAMI IN 1700? 
    The Seattle Times, 14 July 2002


(3) THE NIGHT THE TEKTITES FELL ON GEORGIA
    Space Daily, 16 July 2002

(4) EXPLODING ASTEROIDS MIMIC NUCLEAR ATTACKS
    Die Welt, 17 Juli 2002


(6) BRIGADIER GENERAL PETE WORDEN'S STATEMENT ON THE NEO THREAT
    SIMON P. WORDEN, BRIGADIER GENERAL, USAF

(7) REGARDING THE SMALLER, HIGHER-FREQUENCY IMPACT HAZARD 
    Drake A. Mitchell <PlanetaryDefence@Netscapedot net>

(1) AN IMPACT TRIGGERED MEGA-TSUNAMI IN 1700? 

>From The Seattle Times, 14 July 2002

LEGENDS VALIDATE QUAKE THEORY 
By Elizabeth Murtaugh
The Associated Press

When scientists figured out that seawater drowned groves of tall trees
up and down the coast of Washington state the same year a tsunami hit
Japan, they theorized that a massive earthquake in the Pacific most
likely triggered both events.

Based on Japanese records, scientists were able to pinpoint a date -
Jan. 26, 1700 - and estimate that the rupture of a long stretch of
seafloor had caused a magnitude 9 quake, which would be the largest
known temblor to strike what is now the contiguous United States.

But Ruth Ludwin, a University of Washington geophysics professor, wanted
to know more.

There appeared to be no accounts of cataclysmic earth-shaking in the
stories and legends of the only North Americans who would have witnessed
the quake: Indians.

"When you talk about a very large earthquake in 1700, for that to be
really convincing to me, I really need to have evidence from people who
were there," Ludwin said. "I was looking for a more comprehensive
story."

Ludwin began to search obscure volumes of tribal folklore, where she
found that for centuries, Indians from British Columbia's Vancouver
Island to the coast of Northern California had been telling strikingly
similar tales of mudslides, of plains that suddenly became oceans and
other stories that strongly suggest tribes bore witness to tsunamis like
the one in 1700.

Many of the legends involve a mythic battle between a thunderbird and a
whale.

One tale told by generations of Hoh Indians from the Forks area of
Washington's Olympic Peninsula contains what Ludwin considers the
clearest description of a concurrent earthquake and tsunami yet
discovered in tribal legend.

As the story goes, "There was a great storm and hail and flashes of
lightning in the darkened, blackened sky and a great and crashing
'thunder-noise' everywhere. ... There were also a great shaking, jumping
and trembling of the earth beneath and a rolling-up of the great
waters."

The Makah Indians, whose reservation at Neah Bay sits at the northwest
tip of Washington state, also have a version - one that ends with a
thunderbird delivering a whale inland to the mouth of a river, giving
the giant beast to a tribe that had been starving during a winter
thousands of years ago. 

Although it's unclear exactly how long the story has been told, it
formed the basis of the tribe's centuries-old whale hunt and could be
linked to one of the seven "megathrust" quakes scientists believe have
occurred during the past 3,500 years.

Many legends contain no time elements. Others that were never written
down have been lost entirely, so Ludwin's work can seem like trying to
solve a puzzle with most of the pieces missing. But she says it's worth
it.

"The work that I've done is not extremely important from a scientific
point of view, but it's important from the point of view of
understanding and believing," Ludwin said. "It's another piece of the
puzzle."

The megathrust quake believed to have occurred in 1700 ruptured the
Cascadia subduction zone, where two of the tectonic plates that form the
Earth's crust - the Juan de Fuca and the North America plates - overlap.

>From its northern end, off the western coast of Vancouver Island, the
subduction zone stretches about 600 miles south to Cape Mendocino in
Northern California, then runs into the San Andreas fault.

The Japanese first theorized that an enormous earthquake in the Pacific
caused what they called their "orphan tsunami," so named because there
was no local temblor that accompanied the torrent of 6-foot-high waves
that crashed along 500 miles of coastline.

When they learned that groves of red cedars and Sitka spruces along
Washington's coast had dropped several feet, drowning in saltwater
sometime in the late 1600s or early 1700s, they theorized that one huge
quake must have been responsible for both the Japanese tsunami and this
state's "ghost forests."

Radiocarbon dating of spruce stumps narrowed the timeline of the tree
drownings to somewhere between 1680 and 1720, said Brian Atwater, a U.S.
Geological Survey scientist in Seattle.

That was too big of a window, so scientists went back to one of the
estuaries where roots of red cedars had survived and could be dated by
their rings.

At that grove, near the Copalis River in Grays Harbor County, tree-ring
dating showed the red cedars died sometime between August 1699 and May
1700.

"If we had found that those red cedars died in 1697 or 1703, we would
say, 'Well, we're not sure your tsunami came from our earthquake,' "
Atwater said. "We knew there was an earthquake or a series of
earthquakes. The question was how big and exactly when."

Although the geological evidence of the 1700 megathrust seemed solid,
there were still some skeptics before Ludwin started finding Indian
tales that supported the science.

"People understandably want human evidence as well as physical
evidence,"Atwater said.

Copyright ? 2002 The Seattle Times Company

================
===============
(3) THE NIGHT THE TEKTITES FELL ON GEORGIA

>From Space Daily, 16 July 2002
http://www.spacedaily.com/news/deepimpact-02k.html

by Louis Varricchio
Middlebury - Jul 16, 2002

The Moon is not the geologically dead world that most astronomy
textbooks claim, according to Hal Povenmire, a Florida Institute of
Technology astronomer, long-time meteorite hunter and former NASA
Project Apollo engineer.

In February, NASA officials announced new evidence that the Moon has an
active, molten core. Povenmire concurs with NASA and believes that there
are signs of geologically recent lunar volcanism right here on Earth.

The most recent eruption on the Moon, he claims, showered a portion of
Asia and Australia with many tons of volcanic glass. This so-called
Australasian event occurred within the past million years.

Povenmire's interest in tektites was aroused long before he discovered
both the Upsilon Pegasid meteor shower and a new asteroid, officially
named 12753 Povenmire.

In 1970, realizing that 34.5 million year-old tektite stones found in
Georgia were extremely rare and that their strewn field had never been
mapped, he undertook a monumental effort to learn more about them.

To date, thanks to Povenmire's fieldwork, the size of the Georgia
tektite zone has been expanded from 500 square miles to over 7,000
square miles. The number of Georgia tektites he discovered increased
from 200 to over 1,300.

Povenmire said thousands of tektites might have fallen on prehistoric
Georgia in a single day or night.

Povenmire believes that these natural glass stones are volcanic material
blown off the Moon by eruptions, an idea first proposed by a European
geologist around 1900.

Many scientists disagree with Povenmire's theory, but the Florida
researcher is now convinced that the Moon belches and hurls tons of
obsidian-like debris into Earth's gravity well every few million years.

Tektite falls may also cause climate change and extinctions on Earth, he
said.

Armed with his Georgia fieldwork data, Povenmire refutes the current
theory that tektites were formed when asteroids or comets hit the Earth
and melted sediments and rocks. Tektites, a dry homogeneous natural
glass, he noted, do not resemble wet inhomogeneous impact glass found
around many meteor craters.

Povenmire notes that the slow way tektite glass formed, and the volcanic
features some researchers have observed within chunky, layered tektites,
can't be explained by the widely accepted terrestrial-impact theory.

Ablation studies also prove that the infall velocities of tektites
reached 6 km per second or greater-an unlikely speed for terrestrial
ejecta to attain going up through the atmosphere.

Povenmire likes to point out that cosmic-ray traces inside tektites show
they couldn't come from beyond the Earth-Moon system implying that they
didn't spend a long time in space.

Based on still more circumstantial evidence-such as the fact that
Apollos 12 and 14 astronauts found several lunar highland and subcrustal
rocks with tektite-like chemistry-Povenmire believes the space-science
community needs to drastically rethink what mechanisms caused the
ancient stones to fall to Earth.

Louis Varricchio is a science writer living in Vermont and can be
contacted via (morbius@togetherdot net)

Copyright 2002, SpaceDaily

==============
===================================================

(6) BRIGADIER GENERAL PETE WORDEN'S STATEMENT ON THE NEO THREAT

MILITARY PERSPECTIVES ON THE NEAR-EARTH OBJECT (NEO) THREAT
SIMON P. WORDEN, BRIGADIER GENERAL, USAF
Deputy Director for Operations
United States Space Command
Peterson AFB, CO
July 10, 2002

The opinions and concepts expressed are those of the author and do 
not necessarily represent the position of the Department of Defense 
or the United States Space Command

Introduction

A few weeks ago the world almost saw a nuclear war.  Pakistan and 
India were at full alert and poised for a large-scale war - which 
both sides appeared ready to escalate into nuclear war.  The 
situation was defused - for now!  Most of the world knew about this 
situation and watched and worried.  But few know of an event over the 
Mediterranean in early June of this year that could have had a 
serious bearing on that outcome.  U.S. early warning satellites 
detected a flash that indicated an energy release comparable to the 
Hiroshima burst.  We see about 30 such bursts per year, but this one 
was one of the largest we've ever seen.  The event was caused by the 
impact of a small asteroid - probably about 5-10 meters in diameter 
on the earth's atmosphere.  Had you been situated on a vessel 
directly underneath the intensely bright flash would have been 
followed by a shock wave that would have rattled the entire ship and 
possibly caused minor damage.

The event of this June caused little or no notice as far as we can 
tell.  But had it occurred at the same latitude, but a few hours 
earlier, the result on human affairs might have been much worse. 
Imagine that the bright flash accompanied by a damaging shock wave 
had occurred over Delhi, India or Islamabad, Pakistan?  Neither of 
those nations have the sophisticated sensors we do that can determine 
the difference between a natural NEO impact and a nuclear detonation. 
The resulting panic in the nuclear-armed and hair-trigger militaries 
there could have been the spark that would have ignited the nuclear 
horror we'd avoided for over a half-century.  This situation alone 
should be sufficient to get the world to take notice of the threat of 
asteroid impact.

The Threat

I've just relayed the aspect of the near-earth objects (NEO) that 
should worry us all.  As more and more nations acquire nuclear 
weapons - nations without the sophisticated controls and capabilities 
build up by the United States over the 40 years of Cold War - we must 
first and foremost ensure that the 30-odd impacts on the upper 
atmosphere are well understood by all to be just what they are.

A few years ago those of us charged with protecting this nations 
vital space system, such as the Global Positioning System (GPS) 
became aware of another aspect of the NEO problem.  This was the 
Leonid meteor storm.  This particular storm occurs every 33 years. 
It is caused by the debris from a different type of NEO - a comet. 
When the earth passes through the path of a comet, it can encounter 
the dust thrown off by that comet through its progressive passes by 
the Sun.  This dust is visible on the Earth as a spectacular meteor 
storm.  But our satellites in space can experience the storm as a 
series of intensely damaging micrometeorite strikes.  We know about 
many of these storms and we've figured out their parent comet 
sources.  But there are some storms arising from comets that are too 
dim or spent for us to have seen that can produce "surprise" events. 
One of these meteor storms has the potential of knocking out some or 
even most of our earth-orbiting systems.  If just one random 
satellite failure in a pager communications satellite a few years ago 
seriously disrupted our lives, imagine what losing dozens of 
satellites could do!

Most people know of the Tunguska NEO strike in Siberia in 1908.  An 
object probably less than 100 meters in diameter struck over Siberia 
releasing the equivalent energy of up to 10 megatons.  It leveled a 
forest 50 miles across.  But most people don't know that we have 
evidence of two other strikes during last Century.  One occurred over 
the Amazon in the 1930s and another over central Asia in the 1940s. 
Had any of these struck over a populated area, thousands and perhaps 
hundreds of thousands might have perished.  Experts now tell us that 
an even worse catastrophe that a land impact of a Tunguska-size event 
would be an ocean impact near a heavily populated shore.  The 
resulting tidal wave could inundate shorelines for hundreds of miles 
and potentially kill millions.  There are hundreds of thousands of 
objects the size of the Tunguska NEO that come near the earth.  We 
know the orbits of but a handful.

Finally, just about everyone knows of the "dinosaur killer" 
asteroids.  These are those objects a few kilometers across that 
strike on timescales of tens of millions of years.  While the 
prospect of such strikes grab people's attention - and make great 
catastrophe movies - too much focus on these events has in my opinion 
been counterproductive.  In my organization, the Department of 
Defense, I have tried to raise our concern and interest in addressing 
the very real threats outlined above.  However I get the predictable 
response. "General, if this threat only hits every 50 million years, 
I think we can focus our attention of more immediate threats!"  In 
short the "giggle factor" in the professional scientific and national 
security community has meant that we have gotten little done on this 
problem.

What Should We Do?

First and foremost we must know when an objects strikes the earth 
exactly what it is and where it hit.  Fortunately our early warning 
satellites already do a good job of this task.  And our next 
generation system, the Space-Based Infrared System (SBIRS) will be 
even better.  The primary difficulty here is that this data is also 
used for vital early warning purposes and its detailed performance is 
classified.  However, in recent years the U.S. DoD has been working 
to provide extracts of this data to nations potentially under missile 
attack with cooperative programs known as "Shared Early Warning." 
Some data about asteroid strikes has also been released to the 
scientific community.  Unfortunately this data takes several weeks to 
get released.  Thus my first recommendation is that the United States 
DoD make provision to assess and release this data a soon as possible 
to all interested parties - exercising proper cautions of course to 
ensure that sensitive performance data is safeguarded.

We have begun to scope what an NEO warning center might look like. 
We believe adding a modest number of people, probably less than 10 
all told, to current early warning centers and supporting staffs 
within Cheyenne Mountain could accomplish this.   A Natural Impact 
Warning Clearinghouse has been scoped to do this job.

Perhaps the most urgent mid-term task has already been begun.  This 
is the systematic observation and cataloguing of close to all 
potentially threatening NEOS.  We are probably about halfway through 
cataloging "large" NEOS (greater than a kilometer in diameter).  It's 
interesting to note that the most effective sensor has been the MIT 
Lincoln Lab LINEAR facility in New Mexico.  This is a test bed for 
the next generation of military ground-based space surveillance 
sensors.  But this ground-based system, however effective, can only 
really address the "large", highly unlikely threats.  We find out 
every few weeks about "modest" asteroids a few hundred meters in 
diameter.  These are often caught as they sail by the earth, often 
closer than the Moon, unnoticed until they have nearly passed.  Most 
recently the object 2002MN had just this sort of near miss - this 
time only a few tens of thousands of kilometers from the earth! 
Moreover, ground-based systems such as LINEAR are unable to detect 
one of the potentially most damaging classes of objects, those such 
as comets that come at us from the direction of the sun.  New 
space-surveillance systems capable of scanning the entire sky every 
few days are what's needed.

New technologies for both space-based and ground based surveys of the 
entire space near the earth are available.  These technologies could 
enable us to completely catalog and warn of objects as small as the 
Tunguska meteor (less than 100 meters in diameter).  The LINEAR 
system is limited primarily by the size of its main optics - about 1 
meter in diameter.  By building a set of three-meter diameter 
telescopes equipped with new large-format CCD-devices, the entire sky 
could be scanned every few weeks.  But more important the follow-up 
observations necessary to accurately define orbits, particularly for 
small objects could be done.

The most promising systems for wide-area survey - particularly to 
observe close to the sun to see objects coming at up from that 
direction - are space-based surveillance systems.  Today the only 
space-based space surveillance system is the DoD's "MSX" Satellite. 
This was a late 1990s missile defense test satellite and most of its 
sensors have now failed.  However one small package weighing about 20 
kg and called the "SBV" sensor is able to search and track satellites 
in Geosynchronous orbit using visible light.  This has been a 
phenomenally successful mission having lowered the number of "lost" 
objects in GEO orbit by over a factor of two.  MSX is not used for 
imaging asteroids, but a similar sensor could be.  The Canadian Space 
Agency, in concert with the Canadian Department of National Defense 
is considering a "microsatellite" experiment with the entire 
satellite and payload weighing just kg.  This Near-Earth Surveillance 
System (NESS) would track satellites in GEO orbit, as MSX does today. 
However, it would also be able to search the critical region near the 
sun for NEOs that would be missed by conventional surveys.

The U.S. DoD is planning a constellation of somewhat larger 
satellites to perform our basic satellite-tracking mission.  Today 
our ground-based radars and telescopes, and even MSX only track 
objects that we already know about.  These systems are not true 
outer-space search instruments as the LINEAR system is.  However, the 
future military space surveillance system would be able to search the 
entire sky.  As an almost "free" byproduct it could also perform the 
NEO search mission.  Corresponding, larger aperture ground based 
systems could then be used to follow up to get accurate orbits for 
the NEOs discovered by the space-based search satellites.  Again, I 
believe there is considerable synergy between national security 
requirements related to man-made satellites and global security 
related to NEO impacts.

Regardless of how well we know NEO orbits and how well we can predict 
their impacts the fact remains that today we have insufficient 
information to contemplate mitigating an impact.  We do not know the 
internal structure of these objects.  Indeed, we have reason to 
believe that many, if not most are more in the nature of  "rubble 
piles" than coherent objects.  This structure suggests that any 
effort to "push" or divert a NEO might simply fragment it - and 
perhaps turn a single dangerous asteroid into hundreds of objects 
that could damage a much larger area.

What are needed are in-situ measurements across the many classes of 
NEOs, including both asteroids and comets.  This is particularly the 
case of small (100meter) class objects of the type we would most 
likely be called upon to divert.  Until recently missions to gather 
these data would have taken up to a decade to develop and launch and 
cost 100s of millions of dollars.  However, with the rise of 
so-called "microsatellites" weighing between 50-200 kg and which are 
launchable as almost "free" auxiliary payloads on large commercial 
and other flights to GEO orbit, the situation looks much better. 
These missions can be prepared in one-two years for about $5-10M and 
launched for a few million dollars as an auxiliary payload.  Such 
auxiliary accommodation is a standard feature on the European Ariane 
launched and should be, with proper attention, here in the United 
States on our new EELV launcher systems.

With a capable microsatellite with several kilometers per second 
"delta-V" (maneuver capacity) launched into a GEO transfer orbit (the 
standard initial launch orbit for placing systems into GEO) the 
satellite could easily reach some NEOs and perform in-situ research. 
This could include sample return and direct impact to determine the 
internal structure and potential to physically move a small object. 
Indeed, NASA is planning several small satellite missions.  The key 
point here, however, is that with missions costing $10M each, we can 
sample many types of objects in the next decade or so to gain a full 
understanding of the type of objects we face.

There is an interesting concept to consider.   If we can find the 
right small object in the right orbit we might be able to nudge it 
into an orbit "captured" by the earth.  This would make a NEO a 
second natural satellite of earth.  Indeed, there is at least one NEO 
that is close to being trapped by the Earth now, 2002 AA29.  If such 
an object were more permanently in earth orbit it could not only be 
more closely studied but might form the basis for long-term 
commercial exploitation of space.  Moreover, a very interesting next 
manned space flight mission after the Space Station would be to an 
asteroid, maybe even one we put into earth's gravity sphere.

The key of each of these proposed actions on developing the ability 
to mitigate NEO impacts is that they are all items our national 
security community and we in the United States are likely to do for 
other reasons.  If these efforts can be adapted to the NEO threat 
problem, this would add minimal additional expense.

One of the most important aspects of NEO mitigation is often 
overlooked.  Most experts prefer to focus on the glamorous 
"mitigation" technologies - diverting or destroying objects.  In 
fact, as the military well knows the much harder part is what we call 
"command and control."  Who will determine if a threat exists?  Who 
will decide on the course of action?  Who will direct the mission and 
determine when mission changes are to be made?  Who will determine if 
the mission was successful?  And there are hosts more.

  These command and control issues are those that the military has 
long struggled with.  The NEO community has not faced this essential 
issue.  Indeed, the United States Space Command has just completed a 
concept of operations for the first step in NEO mitigation - a 
Natural Impact Warning Clearinghouse.  This operation is a command 
and control function.  It would be able to catalog and provide 
credible warning information on future NEO impact problems as well as 
rapidly provide information on the nature of an impact.

International Issues

Much discussion has been expended suggesting that any NEO impact 
mitigation should be an international operation.  I would 
respectfully disagree.  International space programs such as the 
International Space Station fill many functions.  An NEO mitigation 
program would have only one objective.  In the latter case a single 
responsible nation and organization would have the best chance of a 
successful mission.  Moreover, the nation responsible would not need 
to worry about giving up national security sensitive information and 
technology as it would build and control the entire mission itself. 
For as pointed out the means to identify threats and mitigate them 
overlap considerably with other national security objectives.

It does, however make considerable sense that the data gathered from 
surveys and in-situ measurements be fully shared among all.  This 
will maximize the possibility that the nation best positioned to 
perform a mitigation mission would come forward.  One of the first 
tasks of the Natural Impact Warning Clearinghouse noted above would 
be to collect and provide a distribution point for such data.

Summary

NEO Mitigation is a topic whose time has come.  Various aspects 
related to NEO impacts, including the possibility than an impact 
would be misidentified as a nuclear attack, are critical national and 
international security issues.  The focus of NEO mitigation efforts - 
both in finding and tracking them and in exploring and moving some 
should shift to smaller objects.  Not only are the near-term threats 
much more likely to come from these "small" objects (100 meters in 
diameter or so), but we might also be able to divert such objects 
without recourse to nuclear devices.

After a suitable class of NEOs are found, microsatellite missions to 
fully explore and perhaps perform test divert operations should 
commence.  The technologies for low-cost NEO missions exist today.

The necessary command and control, sensor and space operations 
technologies and equipment are all "dual use" to the military.  We 
have similar, and in some cases almost identical requirements.  It 
thus stands to reason that strong military involvement and even lead 
in the decades ahead on NEO mitigation is in order.   As the U.S. 
Government considers how to proceed on this critical issue, the major 
role that the military and the technologies it controls should be 
carefully integrated into our overall national work.

===============================================

ON IMPACT FREQUENCY AND NEED FOR A WARNING CENTER

David Morrison

Impact Frequency

In his written statement (above) Pete Worden mentions three large 
impacts during the 20th century, and in his oral testimony he called 
all three of these 100-m class impacts. He wrote: "Most people know 
of the Tunguska NEO strike in Siberia in 1908. An object probably 
less than 100 meters in diameter struck over Siberia releasing the 
equivalent energy of up to 10 megatons. It leveled a forest 50 miles 
across. But most people don't know that we have evidence of two other 
strikes during last Century. One occurred over the Amazon in the 
1930s and another over central Asia in the 1940s. Had any of these 
struck over a populated area, thousands and perhaps hundreds of 
thousands might have perished". Others have made similar comments, 
sometimes also including the dramatic Sikhote-Alin iron meteorite 
fall of February 12, 1947.

Of these four events, the Tunguska impact (June 30, 1908) of an 
asteroidal object nominally 60 m in diameter was by far the most 
dangerous, producing an airburst releasing 5-15 megatons energy. 
Sikhote-Alin was well observed and studied, and more than 40 tons of 
iron were recovered from multiple craters, but the estimated diameter 
of the projectile was no more than 3 meters. The Amazon impact in the 
1930s has been discussed but is based on scattered human reports with 
no supporting physical evidence, and most researchers suspect that 
this impact is spurious. I have not heard anything about the 
Kazakastan impact of the 1940s, and I suspect that is spurious also.

Thus by my count for the 20th century we have one confirmed 60-m 
impactor (Tunguska) and no evidence of anything else approaching this 
size (although of course we would miss most impacts since they would 
occur in the ocean; absence of evidence in this case is not evidence 
of absence). For comparison, the latest estimated frequency of impact 
of 60-meter projectiles is only about once per millennium, rather 
lower than the older estimates of once every couple of hundred years.

Call for an NEO Warning Center

Several participants in the NEO Roundtable called for establishing a 
NEO coordination and warning center. In the summaries by the 
panelists this was a nearly unanimous recommendation. Worden wrote 
above that "We [USAF Space Command] have begun to scope what an NEO 
warning center might look like. We believe adding a modest number of 
people, probably less than 10 all told, to current early warning 
centers and supporting staffs within Cheyenne Mountain could 
accomplish this. A Natural Impact Warning Clearinghouse has been 
scoped to do this job."

It would be interesting to me to understand better what is meant by 
such a warning center. I think everyone can share Worden's concern 
about misidientification of meteors that hit the atmosphere and 
explode with kiloton-scale energies. I certainly support his proposal 
that this information be disseminated more widely and quickly. 
However, these are not what I call "warnings" -- they are timely 
reports on events that have already happened and been observed from 
space.

The only warnings I know of would concern asteroids or comets 
discovered to be on possible impact trajectores. Over the past 6 
years there have been several short-lived "warnings" of possible 
future impacts that were quickly withdrawn as new data and/or better 
orbital calculations became available. Today with multiple 
international centers for calculating orbits and improved data 
sharing, it is likely that there will be fewer such public warnings. 
In fact, the only legitimate warning (if you want to call it that) on 
the books today is NEA 1950DA, with a nominal chance of 1 in 300 of 
an impact in March 2880.

As the NEA surveys increase in power, there will almost certainly be 
additional cases of newly-discovered NEAs that appear for a short 
time to have a possibility of colliding with the Earth. These will 
all be predictions for far in the future, probably at least several 
decades. Some will be reported in the press, but most will be quietly 
checked out and their orbits refined without the glare of publicity. 
Astronomers in several countries today have this computational 
capability. I therefore wonder what is the purpose of the proposed 
warning center, and just what sort of warnings it anticipates issuing?

Perhaps it is worth repeating that none of the proposed surveys is 
designed to look for any NEA on its final plunge to collision with 
the Earth. Indeed, it would be very difficult and non-cost-effective 
to try to design such a "last minute warning" system. The approach 
first articulated a decade ago is to survey the sky, discover NEAs, 
determine their orbits, and predict their future paths. Any potential 
impactor should be picked up decades (or more) in advance. We can do 
this because orbital dynamics is an exact science, and asteroids do 
not change orbits capriciously. This approach will apply as well to 
the smaller NEAs that are discovered in the future as it does to 
those being found today. "Warning" is a word that conveys the wrong 
impression: In my opinion, what we should be talking about are 
long-term predictions, based on a comprehensive survey of NEAs.

+++++++++++++++++++++++++++++++++++++++++++

NEO News is an informal compilation of news and opinion dealing with 
Near Earth Objects (NEOs) and their impacts.  These opinions are the 
responsibility of the individual authors and do not represent the 
positions of NASA, the International Astronomical Union, or any other 
organization.  To subscribe (or unsubscribe) contact 
dmorrison@arc.nasadot gov.  For additional information, please see the 
website: http://impact.arc.nasadot gov.  If anyone wishes to copy or 
redistribute original material from these notes, fully or in part, 
please include this disclaimer. 

MODERATOR'S NOTE: It is interesting to see just how unhappy Dave is about
the recent U.S. Senate Space Roundtable. He has been trying hard to minimise
the threat of smaller impacts with the Earth for much of the
last two decades. It does not come as much of a surprise that he also
tries to rubbish the research of others into small impacts reported
during the 20th century. According to Dave's "count for the 20th century
we have one confirmed 60-m impactor (Tunguska) and no evidence of
anything else approaching this size." He even claims that Tunguska-size
objects (50-60m) hit the Earth's atmosphere on average only once in 1000
years. These claims seem untenable to me given that we are *frequently*
bombarded by small asteroids close in size to the Tunguska object. In
fact, in the last 10 years alone, two asteroids between 30 and 40 metres
across have been detected after exploding in the Earth's atmopshere. It's
time for Dave to wake up and smell the smoke of these recent impacts. BJP

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

(7) REGARDING THE SMALLER, HIGHER-FREQUENCY IMPACT HAZARD 

>From Drake A. Mitchell <PlanetaryDefence@Netscapedot net>

Dear Benny,

As I was under the impression that this is a "scholarly network", I have
tried to be diligent with references to the literature, especially with
references that are links to such documents and other information freely
available on the Web. It is sad to me that such "web links" and even
the many search engines still seem to be a novelty for a Conference in
an
electronic millennium, but then I suppose allowances have to be made -
even for the fact that indispensable volumes in our field, some that are
already many years old, seem to be rarely read in their entirety even
once.

Anyway, although the text appended below is more than six months old, it
does represent some of the latest understanding in the unclassified
literature of the smaller sized impactors, per 15Jul02's topical
inquiry. Regarding non-terrestrial empirical verifications of such
impact
modeling efforts, with a dedicated program we could actually begin
smaller
deflection-based impact experiments on Mars within a decade (sooner for
the Moon). Contrary to widespread misconception, this would be entirely
economically justified by an approach to the NEO hazard that finally
dispensed with our currently interminable "adhocracy."

If Russia's proposal two weeks ago [1] for a $20B human mission to Mars
by 2015 was enhanced, say by a) including their improved particle-bed
reactor rockets using twisted-ribbon mixed-carbide fuel [2] for much
faster travel times, and b)their giving up on NASA and accepting a more
gung-ho China as the third partner to Russia and Europe, we might even
have humans in Mars orbit [3] in time to witness these first impact
events (incidentally, it might also be prudent to test deflections into
Mars-orbit before we try to deflect NEAs into Earth-orbit for proposed
resource harvesting).

Regardless, more encouraging are the recent proposals for increased
instrumentation infrastructure on this planetary body:

"Advocated by the SSES is establishment of a Mars Long-Lived Lander
Network. This grid of Mars science stations would run for at least one
Martian year from spots around the planet. The armada of stations would
complement a suite of planned French NetLander packages, a system
limited in number and spaced across Mars's equatorial region.
Additionally, a Mars upper Atmosphere Orbiter is promoted by the SSES.
This small, dedicated mission can help reconstruct the evolution of the
Red Planet's atmosphere" [4].

It may be rather hard to believe, especially for those in our field that
still live and breathe in a ground-based telescopic paradigm, but the
most recent cost estimate for X2 to detect all the Potentially Hazardous

Asteroids (PHAs) down to 110m is less than $300M, including launches and
seven years of operation. Perhaps even harder to believe is that
detecting the more monstrous number of PHAs down to 10m, which include
the still hazardous ~3% of Iron PHAs, represents an additional
incremental cost on the  order of only ~$70M. These estimates do assume
an adequate telemetry infrastructure.

This text below [5] was reference "[33]" in the most recent CCNet Essay;
I hope it is helpful to Mr. Ebisch and others.

Best,
DAM
--------------------------------
DPS 2001 meeting, November 2001
[41.05] The Role of Asteroid Strength in Impact Damage
J.G. Hills, M.P. Goda (Los Alamos National Lab)

The fragmentation and dispersal of an asteroid in the atmosphere help
determine the damage it can cause (Hills and Goda, 1993, Astronomical J.
105, 1114-1144). Large asteroids are suspected to be rubble piles with
little overall strength. This lack of strength causes them to break up
higher in the atmosphere than would be the case if they had the same
material strength as normal meteorites. The higher elevation breakup
causes them to spread apart more at a given elevation in the atmosphere,
so less of their energy is available for ground impact.

We made computer simulations of such dispersal using asteroids of normal
strength and those with much reduced strength to see if the more
fragmented asteroids produce less damage. We find that these differences
are much greater for irons than for stones, which is not surprising
given
the greater material strength of the irons. Irons with radii less than
about 20 meters lose most of their energy before they reach sea level if
they are of normal strength. If they are rubble piles, they produce
little ground impact damage unless their radii exceed 70 meters. Iron
asteroids have to have radii above these critical values to allow them
to
produce significant craters on land and tsunami in water. If the radius
of an iron asteroids exceeds 200 meters, the size of the crater it
produces is nearly independent of its material strength. Solid-stone
asteroids with radii greater than about 100 meters produce significant
craters. This critical limit is only about 20% larger for rubble-pile
stone asteroids.

Blast damage from stony asteroids is not very sensitive to their
strength. Small iron asteroids, with radii less than about 20 meters,
produce more blast damage if they are solid, because their energy is
dissipated lower in the atmosphere. If their radii exceed this value,
the
weaker asteroid produces more blast damage than the stronger one because
the stronger one loses less of its energy in the atmosphere and more of
it on ground impact.
------
[1] http://www.cnn.com/2002/TECH/space/07/07/russia.mars.ap/index.html
[2] Gehrels et al, 1994, "Hazards...", pp. 1097-1098
[3] http://sepp.org/scirsrch/PhD.html
[4] http://space.com/scienceastronomy/solar_system_020711.html)
[5] http://www.aas.org/publications/baas/v33n3/dps2001/538.htm

==============
(8) RE: ASTEROIDS 'COLD SPARK A NUCLEAR WAR' 

>From John Michael Williams <jwill@AstraGatedot net>

Hi Benny.

RE: ASTEROIDS 'COULD SPARK A NUCLEAR WAR'
 
> >From Press Association, 14 July 2002
> http://www.theherald.codot uk/news/archive/15-7-19102-0-29-1.html
> 
> A SMALL asteroid exploding in the Earth's atmosphere could
> accidentally cause a nuclear war if "trigger-happy" nations mistook it
> for a first strike attack, experts have warned. This has led to
> scientists and military chiefs calling for a new warning centre that
> would make asteroid detections available to governments around the
> world....

This will never work, anonymous scientists and military chiefs
notwithstanding. The temptation to lie, or to interpret negative ("not a
bomb") obervations as lies, will be too strong.

Consider India and Pakistan, ten years from now, with high-speed,
unstoppable antiballistic missiles rearmed with nuclear warheads. If
there was a nuclear war, several hundred MILLION lives would be lost.
Now suppose someone launched a nuclear missile, perhaps by accident
or by the malicious act of an individual, crazed scientist or military
chief.  Or, suppose a comet fragment exploded in the lower atmosphere
over one of these countries:

What would the new warning center report? If it reported NOT an
asteroid, hundreds of millions would die. Investments of dozens of
scientists and military chiefs would be vaporized. If it reported an
asteroid, deaths, damage, and destruction would be limited.  Why should
such a center EVER report that an unexpected explosion in the atmosphere
was not an asteroid?

What MIGHT work, would be a system of sharing openly the technology so
that each nuclear nation could build its own asteroid detection system,
under its own, sovereign control.  There then would be no good reason
for
any country to lie to itself--any more than there would be in the
absence
of such a system, of course.

As a case in point, the article you circulated ends by saying, 

> In the case of the El Al jet, the Ukrainian authorities insisted that
> no missiles had been fired near the plane and suggested the flash
might
> have been a meteor explosion. This now seems the most likely
> explanation.

However, as I recall, the cause of the jet explosion WAS an Ukrainian
missile, as reported at the time by the very US defense systems the
article advocates. Several Ukrainian  officials were fired for denying
responsibility (as they would have done, were they manning an asteroid
observation system). At the time, both Russia and the United States
confirmed that that explosion was a Ukrainian antiaircraft missile.

So much for the veracity of scientists and military chiefs of another
nation.

-- 
                         John
                     jwill@AstraGatedot net
                     John Michael Williams

=============
(9) EIGHTH ANNIVERSARY OF THE SL-9/JUPITER IMPACT 

>From Andy Smith <astrosafe22000@yahoo.com>

Hello Benny and CCNet,

It is a pleasure to contemplate the sunrise, on the eighth anniversary
of our great wake-up call.....the impact of Shoemaker-Levy 9 on Jupiter,
which started on the 16th of July 1994. Many of us, who had become
concerned about the asteroid/comet impact danger, as a result of the
near-miss of asteroid 1989 FC and as a result of the many important
international conferences held in the early 1990's,  were beginning to
wish and to pray for a harmless demonstration of this danger.....and
Gene Shoemaker was certainly in that group. 

We could not have had a more impressive and safe demonstration and
Galileo could not have been better positioned to help us see it.  That
demonstration and all of the things we have learned have added a special
new appreciation for every day of bright sunshine. Many of us have also
developed an increased dedication to doing all we can to inform others
(especially our policy makers) of the dangers, the need for meaningful
and adequately funded NEO early-warning, defense and civil emergency
preparedness programs (which should be international, in scope).

On this day, each year, we salute all of you and all of the earlier
pioneers,in this important quest (over the last century). We thought it
especially appropriate that the presentations were made to the U.S.
Senate, this week and that some of our old friends and supporters from
the House of Representatives, we able to participate. We also salute the
many friends and supporters of planetary protection around the World and
especially the CCNet, the Spaceguard and Space Shield Foundations, the
Planetary Society, the Space Frontier Organization and many other
organizations and individuals,  for helping us to continually
communicate and cooperate.

We will toast the future and effective planetary protection, tomorrow
and we will give thanks for the  progress which has been made. We thank
you all for your contributions.

Cheers

Andy Smith and the International Planetary Protection Alliance

=============
(10) ELECTROPHONIC FIREBALLS

>From Mike Baillie <m.baillie@qub.acdot uk>

Benny, 

Oliver Morton's update on electrophonic sounds from fireballs
left out the fact that Colin Keay, from Australia, has been publishing
papers on the subject for decades. A few examples are given below.  

cheers  Mike 

Keay, C.S.L. 1980 Anomalous Sounds from the Entry of Meteor Fireballs.
Science 210, 11-15

Keay, C.S.L. 1993, Progress in Explaining the Mysterious Sounds Produced
by Very Large Meteor Fireballs, Journal of Scientific Exploration 7 (4),
337-54

Keay, C.S.L. 1995, Continued Progress in Electrophonic Fireball
Investigations, Earth, Moon and Planets 68, 361-8

=================
(11) ARCHAIC ENGLAND 

>From Bob Kobres <bkobres@arches.ugadot edu>

More books encoded in the DjVu format that may be of interest to
readers:
http://djvued.libs.ugadot edu/dbooks.html 

Among them:

ARCHAIC ENGLAND: AN ESSAY IN DECIPHERING PREHISTORY 
FROM MEGALITHIC MONUMENTS, EARTHWORKS, CUSTOMS, 
COINS, PLACE-NAMES, AND FAERIE SUPERSTITIONS, 
BY HAROLD BAYLEY, 1919

http://djvued.libs.ugadot edu/ae/ 
http://djvued.libs.ugadot edu/ae/aeocr.djvu?djvuopts&zoom=100&page=15
. . .

It is a singular coincidence that evidence of a prehistoric
torrent-fire exists certainly in Ireland, where bog-buried
forests have been unearthed exhibiting all the signs of a
flowing torrent of molten fire or lava. According to the
author of Bogs and Ancient Forests, when the Bog of Allen
in Kildare was cut through, oak, fir, yew, and other trees
were found buried 20 or 30 feet below the surface, and
these trees generally lie prostrated in a horizontal position,
and have the appearance of being burned at the bottom of
their trunks and roots, fire having been found far more
powerful in prostrating those forests than cutting them
down with an axe; and the great depth at which these
trees are found in bogs, shows that they must have lain
there for many ages.

No ordinary or casual forest fire is capable of prostrating
an oak or fir tree, and the implement which accomplished
such terrific devastation must have been something volcanic
and torrential in its character.

I am, however, not enamoured of the Atlantean or any
other theory. My purpose is rather to collate facts, and as
all theorising ends in an appeal to self-evidence, it is better
to allow my material, for much of which I have physically
descended into the deeps of the earth, to speak for itself:
-we must believe the evidence of our senses rather than
arguments, and believe arguments if they agree with the
phenomena.
. . .
Taliesin: 
http://djvued.libs.ugadot edu/ae/aeocr.djvu?djvuopts&zoom=100&page=96   
http://djvued.libs.ugadot edu/ae/aeocr.djvu?djvuopts&zoom=100&page=168  
http://djvued.libs.ugadot edu/ae/aeocr.djvu?djvuopts&zoom=100&page=181 
http://djvued.libs.ugadot edu/ae/aeocr.djvu?djvuopts&zoom=100&page=195 
+ banner
http://djvued.libs.ugadot edu/ae/aeocr.djvu?djvuopts&zoom=100&page=342

svastika, Bird of Fire, etc.:
http://djvued.libs.ugadot edu/ae/aeocr.djvu?djvuopts&zoom=100&page=355 

~~~~~~~~~~~~~~~~~~~~~

THE BABYLONIAN LEGENDS OF THE CREATION 
and the Fight between Bel and the Dragon, 
as told by Assyrian Tablets from Nineveh, 1921
http://djvued.libs.ugadot edu/bloc/ 

Bob Kobres
Main Library 
University of Georgia 
Athens, GA  30602 

bkobres@arches.ugadot edu  
http://abob.libs.ugadot edu/bobk




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