CCNet 41/2002 - 26 March 2002

"One hundred years is approximately the time scale for a 10%
probability of an Earth impact by a 100-meter sized near-Earth asteroid,
one capable of causing substantial regional disruption or destruction of
societal infrastructure. This is also the estimated time
(~70 years) necessary to assure the development of an appropriate
mitigation technology and learn how to apply it to an Earth
threatening object. This confluence of timescales gives present
urgency and special interest to consideration of the scientific foundations
on which near-Earth object (NEO) collision avoidance and impact
mitigation technologies must be based."
--Workshop on Scientific Requirements for Mitigation of
Hazardous Comets and   Asteroids, 3-6 September

"What could have caused the mega-tsunami that struck the south east
coast of Australia five hundred years ago? Ted Bryant's book
describes the four causes of tsunami: earthquakes,
undersea landslides, volcanic eruptions/explosions and cosmic
(asteroid or comet) impacts with the ocean. Of these cosmic impacts and
giant landslides are the most likely causes of mega-tsunami."
--Michael Paine, 25 March 2002

"We welcome a little media attention from time to time. We don't
want too much attention, though, because then our colleagues say
we're nuts, trying to increase our funding by scaring the hell out of
--Don Yeomans, National Post, 25 March 2002


    Michael Paine <>

    National Post, 25 March 2002

    The Honolulu Advertiser, 25 March 2002

    Standish EM, Fienga A

    Kaasalainen M, Torppa J, Piironen J:

    Jewitt DC

    Fernandez YR, Jewitt DC, Sheppard SS

    Probert AA

     Wallis D, McBride N

     Mueller TG, Metcalfe L

     Tedesco EF

     McGhee GR


Workshop on Scientific Requirements for Mitigation of Hazardous Comets and
(A Workshop Sponsored by NASA)

Dates: September 3 through 6, 2002
Venue: Hyatt in Arlington, Virginia
Estimated Registration Fee: $150

Background Rationale and Goals for the Workshop

One hundred years is approximately the time scale for a 10% probability of
an Earth impact by a 100-meter sized near-Earth asteroid, one capable of
causing substantial regional disruption or destruction of societal

This is also the estimated time (~ 70 years) necessary to assure the
development of an appropriate mitigation technology and learn how to apply
it to an Earth threatening object (Belton et al, 2001).

These timescales are similar to the typical lifetime of a family from birth
through the death of grandchildren, and can be expected to be of particular
interest to contemporary society.

This confluence of timescales gives present urgency and special interest to
consideration of the scientific foundations on which near-Earth object (NEO)
collision avoidance and impact mitigation technologies must be based.

Programs for the detection of possible impactors are well in hand, and ideas
abound on how to apply the energy required to either disrupt or deflect an
incoming impactor (Hazards due to Comets & Asteroids, T. Gehrels, Ed.,
1994). Yet little published work exists to address the detailed scientific
and technical requirements for avoidance and mitigation technologies, and
whether an adequate knowledge base exists.

The need for space exploration of NEOs is widely recognized (e.g. in the
Spaceguard Survey report, Morrison, 1992; Space Surveillance, Asteroids and
Comets, and Space Debris, USAF Science Advisory Board report, 1997). More
recently, a UK Task Force on NEOs (Atkinson, 2001) recommends that an
international approach be considered that employs a coordinated set of
rendezvous missions based on inexpensive micro-satellite technology.

Even with the publication of such recommendations it is not clear, from what
has been published, that they are offered on a secure scientific and
technical basis. For example, micro-satellite spacecraft do have an
important role to play in the future scientific exploration of NEOs. Yet for
impact mitigation or collision avoidance technologies to succeed, a high
priority must be placed on scientific investigations intimately associated
with the deep interior structure and special material properties of these

Beyond revealing fundamental clues to the origins of planets, knowledge of
the deep interior structure of asteroids and comets is a requirement if one
means to apply whole-body forces to them and achieve predictable results.

To measure and characterize the needed properties encompassing mass, mass
distribution, material strengths, internal structure, shape, and spin state
(Huebner and Greenberg, 2002), novel kinds of spacecraft investigations will
be required. Locally, drilling and digging from the surface can provide some
of these data, but will probably be restricted to a limited depth. Globally,
radio and seismic wave experiments with active sources analogous to those
used in terrestrial exploration may be necessary. This will require the
development of whole new encounter technologies, and may lead to new
mitigation strategies as well.

This workshop will review what is known about the physics and chemistry of
the interiors of small cometary nuclei and asteroids with the purpose of
attaining a geophysical understanding of asteroids and comets in near-Earth
space. In addition, the workshop will work towards the following specific

* Determination of the scientific requirements for those collision avoidance
and impact mitigation technologies that are considered viable. This includes
identification of measurements that are needed and the accuracy that should
be attained.

* Determination of what mission models and instrumentation developments are
needed to make these measurements.

* Construction of a mission and research roadmap for achieving an adequate
level of knowledge on which to base the future development of practical and
reliable collision avoidance and impact mitigation systems.


Atkinson, H. 2001. UK Task Force on Near-Earth Objects. This report is best
acquired through its web page:

Belton, M.J.S., E. Asphaug, W. Huebner, and D. Yeomans 2001. Scientific
requirements for NEO Impact Mitigation. Presented at Asteroids 2001 meeting,
Palermo, Sicily.

Hazards due to Comets and Asteroids 1994. Edited by Tom Gehrels, University
of Arizona Press.

Huebner, W.F., and J.M. Greenberg 2002. Erice Workshop Summary on Physical
and Chemical Properties of Potential Earth Impactors, Meteoritics and
Planetary Science, In Press.

The Spaceguard Survey: Report of the NASA International Near-Earth-Object
Detection Workshop 1992. Edited by David Morrison. Pasadena, CA: Jet
Propulsion Laboratory.

USAF Scientific Advisory Board 1997. Space Surveillance, Asteroids, and
Comets, and Space Debris, Vol 1, Space Surveillance, SAB-TR-9604.

Inquiries and suggestions to: Nalin Samarasinha

NOAO is operated by the Association of Universities for Research in
Astronomy (AURA), Inc. under cooperative agreement with the National Science
Foundation. The USGP represents U.S. scientific, technical, and
instrumentation interests in the international community of the Gemini
project. The USGP is a division of the National Optical Astronomy
Observatories (NOAO). Last updated 20 March, 2002.


by Michael Paine <>

Science of Tsunami Hazards, Volume 20, No 1 (2002) (not online until mid April). A PDF version
of this paper includes colour photographs and can be downloaded from

This article was originally planned as a review of the book "Tsunami: The
Underrated Hazard" by Ted Bryant (Cambridge University Press, 2001).
However, a review by Japanese tsunami expert Kenji Satake appeared in Nature
on 24 January 2002 so I decided, instead, to describe my own investigations
to verify some of the phenomena that are set out in the book.

The book

Ted Bryant is an Associate Professor at the University of Wollongong, on the
south east Australian coast. He is a geoscientist with an interest in
geomorphology. Bryant had studied the coastal features of the area since the
late 1960s. Some things did not add up. He remembers the day in 1989 when he
was examining fresh boulders jammed into a crevice in a cliff well above the
height of any possible storm waves. After eliminating all other explanations
he and his colleague, Bob Young, "were left with the preposterous hypothesis
that one or two tsunami
waves had impinged upon the coast". Bryant began to gather other evidence of
these mega-tsunami, including the overwashing of a headland 130m high.

It is fair to say that many researchers were sceptical about Bryant's
claims. They picked on isolated items of evidence and provided alternative
explanations for the unusual features. It seems, however, that none of the
critics have actually visited the dozens of interesting
sites and considered the convergence of evidence which leads to the
conclusion that mega-tsunami have struck the south east Australian coast in
recent times.

Eventually Bryant decided to set out his research in a book. As well as
describing the mechanisms of alteration of coastal landforms he
comprehensively covers a wide range of topics concerning tsunami: historical
accounts around the world, the physics of tsunami, causes of tsunami and a
review of the risk to coastal populations. Sakate's review in Nature is
mostly complimentary but cautions that "the quality and depth varies greatly
from chapter to chapter" and that "parts of the book lack vigour and
consistency". I do not have the knowledge to make such judgements but I
found the book fascinating and it certainly triggered my curiosity. The
description of bedrock scouring, in which large chunks of rocky headlands
are torn away in a matter of minutes was amazing. Sakate commented that "a
modern example of bedrock scouring would also have made Bryant's arguments
more convincing". I had the same thoughts, and set out to investigate this

Surprising sources of information

An internet search led me to an unlikely source - the Creation Research
Society. It seems that members of this Society are keen to demonstrate that
modern erosional landscapes, such as the Grand Canyon, could have been
formed in a few thousand years. Fortuitously they have gathered
together recent examples of bedrock scouring by catastrophic floods. The
paper "The 1993 Mid-West Floods and Rapid Canyon Formation" by Dr Glen
Wolfrom describes sudden erosional effects at three locations. Wolfrom
reports that water from a spillway "acted like a chisel, a drill, a grinder
and a thousand bulldozers all in one". His pictures show where huge chunks
of bedrock are missing from the streambed below dam spillways.

Another source that popped up from an internet search was research on
Martian geology. I have a long-standing amateur interest in Mars so this
source caught my attention. The Viking spacecraft that orbited Mars in the
early 1970s took pictures of Martian channels that had signs of catastrophic
flooding. Dr Mary Bourke from Oxford University in the UK has studied the
geomorphology of ancient floods in Central Australia as an analogue for
those features on Mars. In one paper she describes erosion of bedrock
including "scour holes generated by macroturbulent vortices" - evidently a
similar process to that which generated the whirlpool features at Bass

Dr Vic Baker from the University of Arizona also studies the Martian
features and has compared them with the strange landforms of the Washington
Scablands in the USA. I contacted Dr Baker by email and, to my surprise, he
told me he would be visiting Ted Bryant in Wollongong the following week. A
quick call to Dr Bryant confirmed that I could tag along while Dr Baker was
shown the tsunami signatures of the area. Fierce rainstorms and dense fog on
the two hour drive to Wollongong could not deter me from joining the tour.

Now if you intend to visit Wollongong yourself and want to experience that
moment of realisation that a mega-tsunami is the only logical explanation
for the coastal landforms then I suggest you read no further because I am
about to reveal some of Ted Bryant's tantalising evidence.

The clues

The northern side of Bass Point is covered by a thick, jumbled layer of
sand, crushed shells, pebbles and boulders - clearly subjected to severe
mechanical action. The explanation is that they have been dumped there when
a mega-tsunami swept over the headland from the south east. We then crossed
to the rugged, exposed south east face of the headland. Here, carved into
the rock, are two giant donut-shaped whirlpool features some 50 metres
across. One is complete and has a central plug (Figure 1). The other is
about three-quarters complete and looks as if a it was being quarried when
work suddenly ceased (Figure 2). Bryant's explanation is that when the
tsunami overwashed the headland giant whirlpools were formed. The outer
edges of the whirlpool started to form secondary vortices ("kolks") that
were highly erosional and tore out chunks of bedrock in a circular path. For
the second whirlpool the tsunami finished before the full circle could be

This mechanism is still regarded as speculative by Sakate. I was unable to
find a modern example of such an action, where before and after pictures of
the changes to bedrock are available. There are however, several other
examples of these erosional whirlpools in the Wollongong area. They do not
appear to be associated with any localised weakness in the rock but do have
similarities in the surrounding terrain - these would influence the
formation of vortices during overwashing by a mega-tsunami.

I tend to think of the whirlpool mechanism as being similar to a rock-face
tunnelling machine that has a large rotating head with smaller rotating bits
on the circumference  (action movies such as "Total  Recall" and "Die Hard
with a Vengeance" have examples of these machines).

Bryant then showed us the clinching evidence. We clambered over the rock
formations to a valley that had a group of boulders at one end. The boulders
were imbricated (stacked like a pile of fallen dominoes). He explained that
the boulders had been carried from the seaward side of a ridge that was more
than six metres above sea level. He pointed out that one of the boulders had
oyster shells attached - it had been scooped up from the shoreline by a
tsunami, carried over the top of the ridge and dumped against the other
boulders (Figures 3 and 4). The shells had been dated to 1500AD, just 270
years before Captain Cook sailed up the east coast of Australia!

After Bass Point we travelled to several spots along the south coast to see
other examples of strange erosion, imbricated boulders and huge sand
deposits in odd places. It is difficult to think of any other explanation
than mega-tsunami for this wide range of features.

The cause

What could have caused the mega-tsunami that struck the south east coast of
Australia five hundred years ago? Ted Bryant's book describes the four
causes of tsunami: earthquakes,
undersea landslides, volcanic eruptions/explosions and cosmic (asteroid or
comet) impacts with the ocean. Of these cosmic impacts and giant landslides
are the most likely causes of mega-tsunami. Landslides are a possible cause
of the Australian mega-tsunami. The shallow continental shelf extends tens
of kilometres from the coast then drops off steeply to depths of 4
kilometres in some places. Major rivers such as the Shoalhaven and
Hawkesbury deliver sediment to the edge of the shelf and this might
periodically tumble down the continental slope. Apparently a thorough survey
of the continental slope that might pick up signs of past landslides only
recently got underway.

In the book Bryant refers to the work of Ward and Asphaug when considering
the possibility that cosmic impacts might have caused mega-tsunami. Their
work suggest that for Sydney the average interval between 10m+ tsunami
caused by cosmic impacts is about 80,000 years (based on Bryant Figure
9.10). My own investigations of tsunami from cosmic impacts led to a paper
in the Science of Tsunami Hazards (Vol 17, No. 3 1999). In that paper I
pointed out major differences between researchers in the estimates of long
range wave heights from impact-generated tsunami. Using the more
conservative estimates of Crawford and Mader I estimate that, for Sydney,
the average interval between 10m+ tsunami from cosmic impacts is about 1
million years. Even the most pessimistic frequency derived from the work of
Ward and Asphaug would not account for frequency of large tsunami
established by Bryant - perhaps every 500 years. There remains, however, the
possibility of an unusual series of impacts such as a barrage from the
breakup of a comet. There are signs of such an event occurring several
thousand years ago (Steel 1995) but it does seem unlikely that "frequent"
ocean impacts large enough to devastate the coast of Australia were not
accompanied by similar large impacts in the northern hemisphere, including
some that would have left impact craters on land. On the other hand the last
major Australian tsunami event, that occurred around 1500AD, has some
coincidences. The largest recorded death toll from a meteorite fall occurred
in China in 1490AD - more than ten thousand died in the city of Ch'ing-yang
Shansi (Lewis 2000). There is also evidence of impact generated fires and
tsunami in New Zealand at this time (Bryant's book).

Finally there is speculation about the enigmatic Balls Pyramid rock outcrop
near Lord Howe Island, between Australia and New Zealand. It is a stunning
sight in the middle of the ocean and looks to me like a giant stone tool
that has had shards flaked off to give a ragged edge (Figure
5). The odd thing is that the vane-like island is aligned in the same
direction as the mega-tsunami that hit Bass Point and possibly the South
Island of New Zealand. In discussions during our tour, Bryant pointed out
that a tsunami tens of metres high could cause the strange features
observed on Balls Pyramid.

My recommendation is that people living near the coast read Bryant's book
and go out looking for some of the tsunami signatures that he describes. You
may discover unsettling evidence that our populated coastlines are
surprisingly vulnerable to these giant waves. An interactive map of the New
South Wales tsunami features, with many new photographs, is now available


Baker V. and Milton D. (1974) 'Erosion by Catastrophic Floods on Mars and
Earth', Icarus  23:27-41.

Bourke M. and Zimbelman J. (2000) 'Australian Paleoflood Systems: An
Analogue for Martain Channel Systems', Proceedings of 31st Lunar and
Planetary Science Conference.

Byrant E. (2001) Tsunami: The Underrated Hazard, Cambridge University Press

Lewis J. (2000) Comet and Asteroid Impact Hazards on a Populated Earth,
Academic Press.

Paine M. (1999) 'Asteroid Impacts: The Extra Hazard Due to Tsunami', Science
of Tsunami Hazards, Vol 17, No. 3 pp155.

Sakate K. (2002) 'Making Waves on Rocky Ground', Nature Vol 415, 24 January
2002 pp369.

Steel D. (1995) Rogue Asteroids and Doomsday Comets, Wiley & Sons.

Wolfrom G. (1994) 'The Midwest Floods and Rapid Canyon Formation', Creation
Research Society Quarterly 31(2): 109 September 1994.


>From National Post, 25 March 2002

Sentry of outer space
A NASA Web site keeps track of asteroids that could cross Earth's path

Chris Knight
National Post
There's good news for anyone trying to calculate the end of the world.
Earlier this month, NASA launched a Web site dedicated to reporting how many
asteroids are in our planetary neighbourhood, how big they are, and how
likely it is that one will crash into Earth.

The site, called Sentry, is operated by NASA's Near Earth Object office.

Sentry offers a mixture of technical data for scientists, and general
information for people who like to gamble on when the world will come to an
end. Donald Yeomans, who manages the office in Pasadena, Calif., calls the
new site, at, a "one-stop shopping place for
information on Near Earth Objects," or NEOs.

A chart on the site shows the size, speed and position of nearby asteroids,
and is updated as new ones are discovered almost daily. Thanks to a
Congressional mandate to find 90% of all very large NEOs by the end of the
decade, NASA, which knew about just 169 NEOs in 1990, has now logged more
than 1,800.

And like the info-graphics on the Weather Channel, the site also provides
animations of NEOs in orbit: Pick an object, then sit back like the occupant
of a time machine and watch the Earth swing around the Sun as the years
click by on a counter and the asteroid follows its own orbital path,
occasionally making a heart-stopping swoosh past Earth.

The asteroid 2002 DO3 is going past us right now. As you read this, it is
sailing past the Earth at 10 kilometres a second. It is about 200 metres in
diameter, big enough to carve a two-kilometre-wide crater if it hit, which
it won't -- this time. Call up its orbit on the NEO site and you can watch
it zoom harmlessly, but frighteningly close, past our planet and off into
deep space. Or look at 2002 EM7, a 60-metre-wide rock that buzzed Earth on
March 8 but was only spotted after it passed by.

Yeomans says the site, which gets thousands of visits a day, is educational
for the public: "They enjoy it and it gives them in a few seconds a view of
what the object looks like.

"And it drives home how it gets close to Earth."

NASA hopes to locate 90% of the estimated 1,000 kilometre-wide-or-larger
NEOs by the end of the decade. As of last Wednesday, the space agency was
tracking 575 kilometre-wide-or-larger NEOs. If one of these were to hit
Earth, the results would be catastrophic -- millions would be killed by an
impact near a populated area, and even an ocean strike would release enough
energy to change the climate for decades. A similar catastrophe is believed
to have wiped out most of the life on Earth 65 million years ago, killing
off the big dinosaurs and setting the stage for our own evolution.

By tracking asteroids, NASA hopes to have enough advance warning, should a
big one be heading toward Earth, to send up a spacecraft to nudge it out of
the way.

While finding NEOs is simply a matter of telescope time and patience,
tracking them is still an inexact science. Once they are discovered (by
taking consecutive pictures of a tiny part of the sky and seeing if anything
moves from one picture to the next), asteroids need to be observed over
several days to get even a rough idea of what their orbits are. Computers
can then predict their movements into the future, but the uncertainty grows
over time -- and every time an asteroid wanders past Earth or another
planet, its velocity changes.

"When you have a close approach, the uncertainties in the object's position
are magnified," says Yeomans. "We have not a clue where the object will be
several decades from now, because it could be anywhere."

He likens asteroids' orbits to railway tracks. "We know where the track is,
we know that it can intersect the Earth's path, but we don't know where it
is on the path. All you can do is come up with a best estimate of where it
will be in the future."

Yeomans says the public is becoming better educated about the risks posed by
asteroids. Nature helped in 1994, when comet Shoemaker-Levy 9 smacked into
Jupiter and space probes delivered pictures of the event. Yeomans also
credits the twin asteroid disaster movies of 1998, Deep Impact and
Armageddon, "both of which were not particularly good, but they did
sensitize the public."

Just outside modern memory, and too remote to have the impact of a Hollywood
film, was the 1908 Tunguska Event, in which an asteroid estimated at 60
metres in diameter crashed in Siberia, destroying 2,200 square kilometres of
forest with the force of a hydrogen bomb.

"You would expect something like that every 200 years or so," says Yeomans.

The NEO Web site is careful not to stir panic. The most dangerous object on
its list is asteroid 2002 CU11, highlighted in soothing green, with the
information that it has about a one-in-100,000 chance of hitting Earth -- in
2049. Even that slight risk is likely to be downgraded as the object's orbit
is more closely calculated. Still, Yeomans' office walks a fine line between
fear and education.

"We welcome a little media attention from time to time," he says. "We don't
want too much attention, though, because then our colleagues say we're nuts,
trying to increase our funding by scaring the hell out of people."

Copyright 2002, National Post


>From The Honolulu Advertiser, 25 March 2002
By Jan TenBruggencate
Advertiser Science Writer

Talk about a big bang - a UH researcher offers evidence indicating that a
swarm of asteroids slammed into Earth, the moon and Mars some 3.9 billion
years ago.

Such an event could have wiped out life on Earth - or helped generate it,
according to University of Hawai'i researcher Barbara Cohen.

Cohen and co-researcher David Kring, of the University of Arizona, put
together diverse bits of information to develop a compelling theory that
could help to explain why the oldest rocks on Earth, the moon and Mars are
all the same age - hundreds of years younger than the main bodies

Their concept is that something jerked a large number of rocks out of the
asteroid belt between Mars and Jupiter, and sent them careening through the
inner solar system. Perhaps it was a burp in the orbit of Jupiter, changing
the gravitation field of the region; perhaps it was the formation of Uranus
and Neptune out of gas clouds; or perhaps it was any of a suggested series
of other events.

"We're looking for the initiating event, and whether it could happen again,"
said Cohen, a planetary scientist with the Hawai'i Institute of Geophysics
and Planetology. That's next in the series of investigations that led to a
paper on the asteroid impacts, "Cataclysmic bombardment throughout the inner
solar system 3.9-4.0 Ga," in the Journal of Geophysical Research (Planets).

Their initial take on the likelihood of recurrence is that this was an
exceedingly rare event.

"We want to know what happened to the Earth because we want to know what
could happen in the future," Cohen said. The evidence suggests that the
asteroid catastrophe 3.9 billion years ago was an exceedingly rare event
that may have been associated with the formation of the solar system, and
therefore highly unlikely to happen again.

The scientists were intrigued by the finding that meteorites known to have
come from pieces of the moon had the same age as a meteorite known to be
from Mars, and the same age as the oldest known rocks on Earth. Because all
three bodies are believed to be older than that, something terrible must
have happened 3.9 billion years ago to cause the effects on all three of

Cohen and Kring feel that a disruption in the asteroid belt dislodged a
cluster of stony bodies that "came winging in" toward the inner planets.
There were so many of them, they crashed into multiple planets and probably
into the sun as well. Cohen said no one has been able to test the theory,
but she believes that Venus and Mercury were probably also hit.

"Eighty percent of the moon was resurfaced by remelting or settled dust,"
Cohen said - an indication of the severity of the impact.

An intriguing question is what impact this might have had on life. There are
some scientists who believe they see the chemical signature of single-celled
life already in place when the impacts took place. But fossils don't appear
for nearly another half-billion years-about 3.5 billion years ago.

"One possibility is that life already existed, and it survived.

Another is that (the asteroid impacts) provided the Earth with heat sources
and organic elements, and helped start life," she said. A third is that life
existed before but was wiped out by the impacts, so it had to start again.

"The impactors likely delivered biogenic materials, although it is not clear
if these were essential for life's origins," the authors said in their

The rogue asteroids slammed into a planet or moon perhaps every 10,000 years
or so - a heartbeat in geologic time. Most were probably sucked into the sun
by its immense gravity. Earth, because its gravity is stronger than the
moon's, probably got more impacts than the moon.

The craters that are the signatures of those impacts are still visible on
the moon, but are gone from Earth. That's because the moon has no weather to
modify the landscape through erosion and lacks Earth's plate tectonics.

On our planet, vast plates cover the surface like the pattern on a soccer
ball. The plates are in constant movement, some sliding under others, with
the rock remelting as it is driven into the depths. The process destroys and
re-forms the land. Only one part of the surface has remained exposed and
represents the oldest rocks on Earth. It's in Canada. On the Canadian
shield, Cohen said, is rock 3.9 billion years old. It shows evidence of
having formed earlier, then being transformed by an event in the time frame
of the presumed asteroid impacts.

Like the moon's, the surface of much of this planet would have been
re-formed by new lava flows and by the settling of the vast clouds of debris
that would have been tossed into the atmosphere with each new impact, she

COPYRIGHT 2002 The Honolulu Advertiser



Standish EM, Fienga A: Accuracy limit of modern ephemerides imposed by the
uncertainties in asteroid masses ASTRONOMY & ASTROPHYSICS  384 (1): 322-328
MAR 2002

Accuracy limits in the ephemerides of the four inner planets, imposed by
uncertainties in the masses of the asteroids, are investigated and
illustrated. We consider present-day knowledge of the asteroid masses
(determined by the IRAS survey, direct dynamical determinations,
ground-based photometry, occultations, etc.), and we model the distribution
of those masses. This distribution is then used in a Monte Carlo study,
repeatedly adjusting the ephemerides to fit the observational data, each
time using a different, but equally-likely, set of asteroid masses. The
differences in the resulting ephemerides are shown. If the full inherent
weighting of the highly accurate ranging data is used, stretching over more
than two decades, the orbits become distorted in right ascension and
declination-as much as 5 kilometers or more. If the ranging is de-weighted
to a level equivalent to the other two coordinates (1-2 mas, determined by
VLBI), then a reasonable ephemeris results, showing uncertainties of 2-3
kilometers. It is also possible to produce an ephemeris which will
extrapolate a year or so into the future at the sub-kilometer level (as is
often required for spacecraft navigation). This can be done by
fully-weighting only the recent observational data. However, the ephemeris
farther from the fitting interval is seen to deteriorate rapidly.

Fienga A, CALTECH, Jet Prop Lab, JPL 301-150, Pasadena, CA 91109 USA
CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA
Inst Mecan Celeste & Calculs Ephemerides, F-75014 Paris, France

Copyright 2002 Institute for Scientific Information


Kaasalainen M, Torppa J, Piironen J: Binary structures among large asteroids

The imaging of well-observed large asteroids by lightcurve inversion has
revealed objects, such as 44 Nysa and 41 Daphne, that are distinctly
asymmetric and globally very different from equilibrium-like figures,
indicating contact-binary structures. The shape of the Trojan asteroid 624
Hektor is very probably globally bifurcated. Together with the known large
binary asteroids 216 Kleopatra, 90 Antiope, and 617 Patroclus, these
findings indicate that a nonvanishing portion of large asteroids have binary

Kaasalainen M, Helsinki Univ Observ, POB 14, Helsinki 00014, Finland
Helsinki Univ Observ, Helsinki 00014, Finland

Copyright 2002 Institute for Scientific Information


Jewitt DC: From Kuiper belt object to cometary nucleus: The missing ultrared
ASTRONOMICAL JOURNAL  123 (2): 1039-1049 FEB 2002

We combine new and published data to show that the optical color
distributions of cometary nuclei and Kuiper belt objects (KBOs) are
significantly different. The nuclei are, as a group, bluer than the KBOs,
indicating that the surface chemical and/or physical properties of the two
types of bodies are different. Objects in the dynamically intermediate
Centaur class have optical colors like those of KBOs, while the color
distribution of candidate dead comets is indistinguishable from that of the
cometary nuclei. We infer that the surfaces of KBOs are modified upon entry
to the inner solar system. We consider several mechanisms and conclude that
the color change is most likely caused by the rapid burial of ancient
surface materials exposed in the Kuiper belt. The distinctive, ultrared
material that is present on the surfaces of some KBOs is absent on the
cometary nuclei.

Jewitt DC, Univ Hawaii Manoa, Inst Astron, 2680 Woodlawn Dr, Honolulu, HI
96822 USA
Univ Hawaii Manoa, Inst Astron, Honolulu, HI 96822 USA

Copyright 2002 Institute for Scientific Information


Fernandez YR, Jewitt DC, Sheppard SS: Thermal properties of Centaurs Asbolus
and Chiron
ASTRONOMICAL JOURNAL 123 (2): 1050-1055 FEB 2002

We have measured the mid-infrared thermal continua from two Centaurs,
inactive (8405) Asbolus and active 95P = (2060) Chiron, and have constrained
their geometric albedos, p, and effective radii, R, with the standard
thermal model for slow rotators. These are the first such measurements of
Asbolus; we find R = 33 +/- 2 km and p = 0.12 +/- 0.03. This albedo is
higher than all of those confidently known for active cometary nuclei. The
thermal inertia is comparable to or lower than those of main-belt asteroids,
the Moon, and Chiron; lower than those of the icy Galilean satellites; and
much lower than those of near-Earth asteroids. For Chiron, we find R = 74
+/- 4 km and p = 0.17 +/- 0.02. While this albedo is consistent with the
established value, previous radiometry by others implied a larger radius.
This discrepancy may be partially due to a varying infrared dust coma, but
all data sets have too low signal to be sure. Four Centaur albedos (out of
about 30 objects) are now known. They show a diversity greater than that of
the active comets, to which they are evolutionarily linked.

Fernandez YR, Univ Hawaii Manoa, Inst Astron, 2680 Woodlawn Dr, Honolulu, HI
96822 USA
Univ Hawaii Manoa, Inst Astron, Honolulu, HI 96822 USA

Copyright 2002 Institute for Scientific Information


Probert AA: Fight asteroids with nukes


Wallis D, McBride N: Planetary impact crater analysis with eigenfunction

High-resolution topography has recently become available for a number of
planetary bodies such as the Moon, Venus, Mercury and particularly Mars,
with the 32nd-degree global Martian topography from the Mars Orbital Laser
Altimeter on Mars Global Surveyor. Gridded digital elevation models (DEMs)
of impact craters can be extracted from these data, and provide an extensive
record of planetary impact crater morphologies. It may not be immediately
obvious, however, how crater DEMs can be compared, particularly if there are
many thousands of individual measurements. Comparison is greatly simplified
if the measurements are reduced to an eigenfunction expansion, using the
coefficients of expansion for quantitative shape comparison. Four eigenvalue
expansions are compared for their suitability: a one-dimensional Fourier
sine expansion of a crater cross-section; a two-dimensional Fourier sine
expansion; the eigenfunctions of a vibrating circular membrane; and the
Zernike polynomials. All are found to be suitable except the two-dimensional
Fourier expansion, which fails to converge well on the data because of
inappropriate geometry. Expansion spectra of four Martian impact craters,
each representing a different class of planetary crater morphology, are
calculated with the three suitable methods. The relevance of symmetry (about
the crater centre for cross-sections and radial symmetry for two-dimensional
expansions) is discussed. Finally, a preliminary survey of Martian impact
crater shapes is made, using eigenfunction expansion, which shows three
distinct clusters of Martian crater morphology.

Wallis D, Open Univ, Planetary & Space Sci Res Inst, Milton Keynes MK7 6AA,
Bucks, England
Open Univ, Planetary & Space Sci Res Inst, Milton Keynes MK7 6AA, Bucks,

Copyright 2002 Institute for Scientific Information


Mueller TG, Metcalfe L: ISO and asteroids

We are currently at the end of ISO's 3.5 year Post-Operations Phase and the
start of the 5 year Active Archive Phase. Final automatic bulk processing of
the observations has concluded and all observations are publicly available
from the ISO archive. Here, in addressing ISO's observations of asteroids we
attempt a complete overview, from the original scientific ideas-to the
current results-to what can be expected in the future. ISO has delivered a
wealth of new and unexpected results concerning asteroids, but the archive
still has many hidden treasures. In the near future, ISO's mid- and
far-infrared data, in combination with other observations, will provide new
advances in our understanding of the Solar System and new insights into the
interrelations between meteorites, asteroids, comets and interplanetary
material, all of which play fundamental roles in the Solar System's history
and evolution.

Mueller TG, ESA, Directorate Sci Programmes, ISo Data Ctr, Dept Space Sci,
Villafranca, Spain
ESA, Directorate Sci Programmes, ISo Data Ctr, Dept Space Sci, Villafranca,

Copyright 2002 Institute for Scientific Information


Tedesco EF, Noah PV, Noah M, Price SD: The supplemental IRAS Minor Planet
ASTRONOMICAL JOURNAL 123 (2): 1056-1085 FEB 2002

We present additional and revised IRAS diameters and albedos for the 1992
IRAS Minor Planet Survey (IMPS). Using orbital elements for 26,791 numbered
asteroids, we found 2228 different multiply observed asteroids associated
with IRAS sources, an increase of 432 (24%) over IMPS. The IRAS sample of
small asteroids, diameters D < 20.0 km, has increased by 72% ( from 306 to
526), the sample of Jupiter Trojan asteroids by 77% ( from 39 to 69), and
the sample of small Trojan asteroids (D < 80 km) by nearly a factor of 3
(from nine to 26). We present the entire Supplemental IRAS Minor Planet
Survey data set, describe how it was created, compare it with the IMPS data
set, and estimate how many more asteroids remain to be found in the IRAS

Tedesco EF, Terrasyst Inc, 59 Wednesday Hill Rd, Lee, NH 03824 USA
Terrasyst Inc, Lee, NH 03824 USA
Mission Res Corp, Nashua, NH 03861 USA
USAF, Res Lab, Space Vehicles Directorate, Hanscom AFB, MA 01731 USA

Copyright 2002 Institute for Scientific Information


McGhee GR: The 'multiple impacts hypothesis' for mass extinction: a
comparison of the Late Devonian and the late Eocene PALAEOGEOGRAPHY
176 (1-4): 47-58 DEC 25 2001

Application of the lag-time multiple impacts hypothesis [Poag. 1997b,
Palaios 12, 582-590; Poag et al., 2001. Columbia Univ, Press] to the Late
Devonian leads to the prediction that the Frasnian-Famennian pulsed
extinctions were triggered by a rapid drop in global temperature that
followed an impact-produced anomalous warm interval, which interrupted the
global cooling trend from the Middle Devonian greenhouse to the Early
Carboniferous icehouse. In actualistic comparison with the late Eocene, the
lag-time multiple impacts hypothesis would predict that a Frasnian interval
of multiple impacts should have occurred between 367.7 and 366.7 Ma. The
fact that three impacts (the Alamo, Siljan and Flynn Creek) do occur either
within this predicted interval, or close to it in time, is corroborative
evidence that the lag-time multiple impacts hypothesis may indeed provide
the causal mechanism for the Frasnian-Famennian mass extinction. Based on
the application of the lag-time multiple impacts hypothesis to the
Frasnian-Famennian mass extinction, it is here suggested that future
searches for evidence of impact events in the Late Devonian be concentrated
in strata that occur in the Frasnian transitans to Early hassi zonal
interval, and not in strata immediately below or above the
Frasnian-Famennian boundary. (C) 2001 Elsevier Science B.V. All rights

McGhee GR, Rutgers State Univ, Wright Rieman Labs, Dept Geol Sci, New
Brunswick, NJ 08903 USA
Rutgers State Univ, Wright Rieman Labs, Dept Geol Sci, New Brunswick, NJ
08903 USA

Copyright 2002 Institute for Scientific Information

CCNet is a scholarly electronic network. To subscribe/unsubscribe, please
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attached information may not be copied or reproduced for any other purposes
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DISCLAIMER: The opinions, beliefs and viewpoints expressed in the articles
and texts and in other CCNet contributions do not necessarily reflect the
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"According to Alan Willoughby, we are now in a unique time interval
in all of past and future human history. We are emerging from the "age
of ignorance" where we had neither the knowledge of NEOs nor the ability to
defend ourselves from the threat. We hope to enter the "age of controlled
destiny" early in [this] millennium where we will have both the
knowledge and the capability to defend. In our present interval, we are in
an "age of blindness and inexcusable incompetence" which this author
(pessimistically) judges to be about 200 years."
--George J. Friedman, University of Southern California,


>From, 26 March 2002

In the past six months, while the world focused on the continuing threat of
global terrorism, as many as a dozen or more asteroids sneaked up on the
Earth and zoomed by at distances just beyond the Moon's orbit and closer.
Most were never noticed. Earlier this month, astronomers did spot one. Four
days after it flew by.

In discussing these events, experts describe a planet vulnerable to an
unexpected attack that could, in an instant, wipe out a city or even destroy
civilization. Some researchers go so far as to view the asteroid threat as
an "international emergency situation," as Andy Smith of the Safety Research
Institute in Albuquerque New Mexico said last week.

Yet as billions upon billions of dollars are spent to provide insurance
against terrorism, astronomers were foiled in a recent attempt to encourage
Australia to invest a comparatively paltry $1 million to scan the mostly
unsurveyed southern skies for killer space rocks.

The scientists were practically laughed at on television by the science
minister of Australia who, like much of the world's public, simply does not
take the threat of asteroids seriously.

The reason is simple: The Dread Factor is not high enough.

Paul Slovic, author of "The Perception of Risk" (Earthscan, 2000), says most
people are far more worried over what humans and technology can do to them
than they are about natural disasters. While terrorism, chemical spills and
nuclear accidents are awarded high "Dread Factor" marks by most people,
asteroids, earthquakes and hurricanes rate low.

Stealth approach

On March 8, a hunk of stone and metal about the size of an 18-story
building, made its closest approach to Earth, passing roughly 298,400 miles
(480,200 kilometers) from the planet, just a bit farther out than the Moon,
but a little too close for comfort for most astronomers.

But what was most disturbing was that the asteroid, later named 2002 EM7,
passed virtually unseen. Not until March 12, when it had moved out of the
glare of the Sun and into the night sky was it seen from Earth.

And it was not alone: On Jan. 7, an asteroid the size of three football
fields came within two lunar distances and was spotted only a month before.
Last October, a smaller asteroid passed by at a similar distance and was
detected just two days prior.

For each nearby asteroid that is spotted, several pass entirely unnoticed,
some closer to us than the Moon, scientists say. One researcher estimates
that each year, 25 asteroids roughly as large as 2002 EM7 whiz by at even
closer distances.

They slip through because of limitations to technology, telescope time, and

These close brushes illustrate a message that asteroid researchers have
repeatedly tried to hammer home to politicians and the public: The number of
undiscovered asteroids far exceeds the known list, and the list needs to be
filled out before it's too late.

Asteroid 2002 EM7 left a a pretty ominous message on its own: Only a
tremendously expensive new telescopes -- placed outside Earth's orbit so as
to monitor the blind spot created by the Sun -- could guarantee we won't
suffer an unexpected and sudden impact. There would be a flash of brilliant
light in the sky, and seconds later the world would change forever in a way
that would render Sept. 11 an insignificant memory.

Dread Factor vs. reality of risk

Scientists develop asteroid risk statistics by estimating the total number
of objects that exist and by studying evidence of past encounters -- big
holes in the ground called impact craters.

>From these clues, they say your chances of death by asteroid are about the
same as dying in a plane crash, roughly 1-in-20,000 during your lifetime.
You're more liable to be electrocuted to death (1-in-5000 chance), succumb
to skin cancer or be killed in a car crash.

Yet asteroids pose more risk than tornadoes (1-in-60,000 chance),
rattlesnake bites or food poisoning.

If Earth is hit, you could die by direct impact and vaporization. Or you
might be killed in an associated earthquake or volcanic eruption as the
planet's bell is rung like never before in recorded history. Or perhaps like
countless lesser species, you'll die a slow, agonizing death of starvation
as the world's food supply dwindles in the face of reduced sunlight caused
by a global debris cloud.

Yet if you're like most people, you are not all that worried, according to
sociologists and psychiatrists who study these things.

Slovic, the author, also works at Decision Research, an organization in
Oregon that advises industry and government about risk. He says we do not
base our fears on statistics. Instead, each of us develops our own personal
Dread Factor for various frightening scenarios based on personal experience,
knowledge and, more important, our sense of the situation.

Emotion has replaced instinct as a major risk-assessment tool for modern
humans, who face myriad dangers, none of which involve sneaking up on woolly
mammoths from behind a tree.

"It is more of a gut feeling," Slovic says. "Does it worry me? Does it scare
me? Does it make me uneasy?"

Cars are low on most individuals' Dread Factor lists, even though the
average American stands about a 1-in-100 or 1-in-200 chance of dying in an

"We don't dread cars," Slovic says. "Things that cause cancer are high on
the Dread Factor."

Scientists vs. voters

The Dread Factor, or lack of it, can drive political funding decisions.

The U.S. Congress apparently perceived the threat real enough to require
NASA to make asteroid hunting a serious business. The space agency spends
$3.55 million each year searching for and studying asteroids. (Much of that
money goes to space-based research of asteroids that pose no threat.)

Individual search programs provide much of their own institutional funding.
And amateur astronomers around the globe contribute to the effort. Not
everyone, however, sees an urgent need.

The Australian Science Minister Peter McGauran, appearing on his country's
60 Minutes television program March 17, called the effort to find
potentially threatening asteroids "fruitless, unnecessary, self-indulgent"
and promised no funds unless researchers provide a more convincing argument
for the need.

To the consternation of many researchers, there are no telescopes below the
equator devoted to searching southern skies for asteroids. Australia cut
funding to one such effort in 1996.

An ongoing online poll taken in conjunction with the televised program found
overwhelming support -- 91 percent at last count -- for reinstatement of the
funding. But these votes were cast by people who watched an animated
asteroid slam into Earth and listened to leading experts spout frightening
statistics and detail the grim outcomes they say are only a matter of time.

You and most other voters, in Australia and around the world, probably lean
more toward McGauran's sentiment. According to experts in risk assessment
and fear management, McGauran's starkest statement likely reflects the
general public mood: "I lie awake worrying about a lot of other things.
Near-miss asteroids is not one of them."

The average person tends to be much more afraid of industrial accidents, for

As with terrorism, vast sums of money are spent, as Slovic puts it, "to take
small risks of chemical and radioactive pollution and reduce them even
further. We spend a huge amount for every statistical life saved. On the
other hand, if you wanted to get people to spend money on asteroid
protection or earthquake mitigation, it's very difficult, even though the
risk is much greater."

Richard Taylor of the Probability Research Group, a global affiliation of
researchers looking into various science topics, thinks there is a clear
message in the fact that nations spend billions on military defense but zero
scanning our entire Southern Hemisphere flank for asteroids:

"We feel more at danger from man than from Nature," Taylor says.

Not in my lifetime

A decade ago, Slovic and some colleagues conducted a test. They provided a
group of university students with information about the threat from beyond,
explaining that a giant asteroid was thought to have killed off the
dinosaurs, and others would surely hit the planet at statistically
determined intervals. Then they surveyed the students to determine how they
assessed the risk. The students recognized the threat, but chose not to
worry about it.

"They're expectation was, well, it's not going to happen in my lifetime,"
Slovic says.

If astronomers were to announce an imminent collision, asteroids would
suddenly develop a high Dread Factor, Slovic figures. But because none of us
has any direct experience whatsoever with deadly space rocks, "People don't
get worked up about it. There's too many things to worry about."

Scientists find it similarly difficult to generate much public worry for
other potential calamities, like horrible storms, droughts and coastal
flooding that might result over the next century due to climate change, but
which are seen as remote in time.

There is little chance that the complacent attitude of the public, and of
some government officials, will ever elevate to the level of concern
maintained by asteroid experts. As Slovic says, it's common for scientists
and technicians to have a different and more rational understanding of the
risks involved in their area of study.

Fear as a motivator

Many astronomers, it must be noted, believe present asteroid search efforts
are fairly adequate, notwithstanding the lack of a southern telescope. With
time, they say, the worst threats will be rooted out, which is to say the
largest asteroids. And, they argue, the odds are that if any globally
destructive object is found to be on a collision course with Earth, there
will probably be years of warning.

A more vocal group of astronomers and other proponents of increased spending
tend to worry about smaller asteroids that could cause regional devastation.
And they tend to make more frightening statements. Here are just a few that
have come from the mouths of respected experts just in the past 10 days:

"If it were over a populated area, like Atlanta, it would have basically
flattened it," asteroid cataloguer Gareth Williams told CNN in discussing
the potential of asteroid 2002 EM7.

"We live in a cosmic shooting gallery," said Duncan Steel of Salford

"We're talking about a million megaton explosion," said author and physicist
Paul Davies of Macquarie University, in discussing a typical impact on
another recent television program. "That's a million city-bursting bombs all
going off at once."

While such statements are often softened with the reminder that the world
probably won't end tonight -- Davies said in the next breath, "I don't want
people to lie awake at night worrying about it" -- the effort is clear: Get
you and the politicians to act on this threat.

Yet in a world remade by a single day of terrorism, fear may be doomed as a
sales pitch, just as it was in Australia.

Fear is not something that can necessarily be instilled by scientists.
Instead, it tends to be generated by whatever rears its ugly head and shouts
loudest, explains Robert Butterworth, a psychologist at International Trauma
Associates in Los Angeles. Nothing right now, globally speaking, can measure
up to the fear of terrorism and the associated potential of a nuclear

I can't take it

While there are plenty of things for a 21st Century human to worry about, we
all have our limits.

"In order for us not to have these things on our minds, we use a device
that's been maligned in last few years, which is denial and repression,"
Butterworth says. "We push it back, because we couldn't function if we

Asteroids, like a fear of bugs or concern over a missed appointment, can be
lost in a shuffle of frightening thoughts. Some things just aren't as
significant as they seemed last summer.

Butterworth puts it this way: "If we had been walking with a limp and all of
a sudden were shot in the stomach, the limp fades away."

No place has been hit in the stomach like New York City. Psychologist Janice
Yamins, whose patients include victims of the terrorist attacks, says
residents are stunned by their own change in views, such as newfound support
for defense spending "instead of other things that won't help preserve our

Where fear leaves off, anger and revenge step in.

Natural disasters don't generate similar sea changes in philosophy.
Californians suffer tremendously from earthquakes every few years. They pick
up and move on. Southeast coastal residents rebuild time and again after
hurricanes. People there shrug off the threat. Butterworth figures an
asteroid impact would generate similar reactions.

"What do we do, shake our fist at God?" he asks. "Who can we be angry at?"

All this psychology lends support to a notion that has already formed in the
heads of many astronomers: Their call for more funding will fall on a whole
lot of deaf ears until another asteroid makes real noise.

The last serious impact was in 1908, when a rock about the same size as 2002
EM7 exploded above the surface of Siberia. Roughly 1,200 square miles (3,108
square kilometers) of forest were flattened in a remote region known as
Tunguska. There were no known deaths, because almost no one lived there.

The odds of a similar event, which could easily destroy a large city or a
small state with miles of extra destruction to boot, are about 1-in-20 over
the next 50 years.

Knowledge and false alarms

In the past decade, about 500 very large space rocks have been found to
wander near the space shared by Earth's orbit. These so-called Near Earth
Asteroids, all larger than 1 kilometer (0.6 miles), represent about half the
expected total. Millions of smaller asteroids are almost entirely

The larger rocks are the ones many scientists fear most. If one hit Earth,
civilization would be pushed to the brink and perhaps beyond. Deaths could
easily be counted in millions, possibly even billions. Many species of
plants and animals would disappear.

As more asteroids are discovered and publicized, public awareness of the
threat grows. But the information is not always accurate.

In a couple of high-profile cases, most prominently four years ago with an
asteroid called 1997 XF11, the public was warned of potentially devastating
impacts before further calculations showed the newly found rocks to be no
threat at all.

Worse, late-night radio programs and various web sites spout all sorts of
unscientific claims of impending asteroid doom, reports that spread like
tsunami radiating outward from an ocean impact. Any reporter who covers the
subject has gotten more than a few frantic e-mails from concerned citizens
who heard this or that and were worried about the planet-destroyer coming
next June, or whenever.

Movies like Armageddon only enhance "wild inaccuracies" in some minds, says
Taylor of the Probability Research Group.

All of this -- the fact, the fiction, the unfounded fears and the genuine
threats that some people don't fear at all -- create a gulf of apathy and
misunderstanding that may well prevent asteroid experts from convincing you
to see the world as they see it.

Several dozen professional astronomers, meanwhile, maintain a nightly vigil
in the Northern Hemisphere, scanning immense and dark skies for tiny points
of light, then struggling to observe often minor movements against the
background of stars in order to determine a trajectory, an ultimate

Always on their minds: Will this one hit Earth?

"It isn't a matter of if one of these things is going to hit the Earth,"
said Duncan Steel on the 60 Minutes broadcast. "It's just a matter of when.
Either we can expect 23 years warning or six or seven seconds."

For those in the know, the asteroid Dread Factor is off the charts.

Copyright 2002,

CCNet is a scholarly electronic network. To subscribe/unsubscribe, please
contact the moderator Benny J Peiser < >. Information
circulated on this network is for scholarly and educational use only. The
attached information may not be copied or reproduced for any other purposes
without prior permission of the copyright holders. The fully indexed archive
of the CCNet, from February 1997 on, can be found at .
DISCLAIMER: The opinions, beliefs and viewpoints expressed in the articles
and texts and in other CCNet contributions do not necessarily reflect the
opinions, beliefs and viewpoints of the moderator of this network.

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