CCNet DIGEST, 27 July 1998
From a very tired but happy father - and many thanks for all your
good wishes. Benny J Peiser
(1) NO ASTEROID IMPACT IN 2028
Brian G. Marsden (email@example.com)
(2) REEL SCIENCE: ASTEROIDS MAKE A BIG HIT
From the BOSTON GLOBE
(3) MOVIE PRODUCERS CHALLENGED TO MATCH NEO GRANT
Duncan Steel <firstname.lastname@example.org>
(4) NEW IMPLICATIONS FOR A TAURID METEOROID SWARM
D.J. Asher*) and K. Izumi, COMMUN RES LABS, JAPAN
(5) GREENLAND EXPEDITION
Henrik Persson <email@example.com>
(6) MAGMA'S MAKEUP YIELDS NEW CLUES TO CATASTROPHIC ERUPTIONS
Andrew Yee <firstname.lastname@example.org>
(1) NO ASTEROID IMPACT IN 2028
From Brian G. Marsden (email@example.com)
While borrowing the above title from a subsection of Clark
Chapman's article on page 18 of the July-August issue of "The Planetary
Report", I could not help pondering on how he knows, for sure, the
statement to be true. After all, Clark is the man who this past May
told a U.S. Congressional committee that "a mile-wide asteroid could
hit tomorrow and we wouldn't even know it was coming".
Until reading this issue of "The Planetary Report" I had not fully
appreciated the point that Clark "published a neighborhood newspaper
and studied journalism as a teenager". But this makes some sense, for
the plenitude of misconceptions and outright mistakes in his item
matches that of the very worst examples of newspaper journalism. He
should indeed "rethink [his] own responsibilities to 'get it right'".
The anonymous astronomer blamed in the subsection did not actually
speak of "a mile-wide asteroid that just might strike the earth, with
horrible consequences" on a specific date in 2028. What he said was
that "a little more than 30 years from now ... the chance of an actual
collision is small, but one is not entirely out of the question".
Maybe the difference is subtle, as is frequently intentionally the case
between statements that one might consider making in either positive or
negative terms, but it is also hardly the case that "the story was
retracted the next day, ostensibly because new data were obtained".
For one thing, there was really nothing to retract, because the whole
point of the story was that there was indeed a need for "new data".
With wonderful speed, those new data were forthcoming the very next
day, data that neatly and unequivocally refined the computation of what
remains the closest non-immediate known approach of an asteroid to the
earth during the next eight decades and more.
As for checking "with his colleagues before shouting to the world",
the particular astronomer certainly checked with enough of them to know
that there was little of consequence wrong with his calculation, and it
is clearly on record that four or five of them later obtained virtually
identical results. The "exclamation mark" referred, not to any
suggestion of an earth impact, but to the result of this very specific
computation, completely confirmed by others.
If Chapman thinks that the particular astronomer contributed to
"another failure of peer review in the Information Age", he should
consider applying that same criticism to the one who remarked on "zero
probability of impact, folks" (while at the same time providing numbers
that were quite inconsistent with this), as well as to himself for
denying that new data were needed before the asteroid could be declared
"certifiably safe". In the CCNet Digest on June 8 I demonstrated
rather clearly that, in the absence of the 1990 precovery data, we
should NOT now be in a position to say that 1997 XF11 would NOT strike
the earth in 2037.
Earlier this month, I attended an IAU Colloquium in Namur, Belgium,
rather prophetically entitled "Impact of Modern Dynamics in Astronomy".
In addition to talking orbits with international colleagues who really
know about them, it was a pleasure to get away for a few days from
backbiting critics in the U.S. and enjoy with those colleagues an
evening of camaraderie in one of the local bars showing the
well-matched Brazil-Holland battle on its big screen. There was broad
agreement that the dynamical problem of 1997 XF11 was one of pure
chaos, and that in order even to begin to appreciate it, it is
necessary to get away from the confines of purely linear analyses and
Gaussian distributions of observational errors. Amplifying somewhat on
my remarks in the June 8 CCNet Digest, I demonstrated an even better
case of a possible earth impact (a Deep Impact, in fact) of 1997 XF11
on 2040 Oct. 26.76 UT, seven revolutions after the 2028 encounter.
Like the "2037" computation, it is in fully acceptable agreement with
the 1997-1998 observations. This solution requires the object to come
to just twice the lunar distance in 2028 and misses the 1990
observations (fortunately confirmed on more than one night) by less
than 2 arcmin. Here is a close approximation to the starting elements:
Epoch 1998 July 6.0 TT = JDT 2451000.5 Marsden
M 210.53210 (2000.0) P Q
n 0.56931495 Peri. 102.48695 +0.72522768 +0.68734323
a 1.4417866 Node 214.11730 -0.65617993 +0.67238812
e 0.4837077 Incl. 4.09477 -0.20850110 +0.27468801
P 1.73 H 17.0 G 0.15
Another intriguing solution, a variant of one I briefly mentioned
on June 8, has 1997 XF11 in 4:7 resonance with the earth after 2028,
but the approach distance in 2035 is then so small (25 000 km) that the
object jumps to a 2:3 resonance (revolution period 1.5 years) and has
another earth encounter in 2038. With a calculated minimum distance of
45 000 km, Clark may feel that the object would be "certifiably safe"
in 2038, but he perhaps has more faith in Gaussian error distributions
and numerical integrations run through near singularities than I have.
In any case, if one considers only the "2037" and "2040" results, the
fact is that 1997 XF11 is the only real object for which it has been
demonstrated that observations made over more than a day or two are
entirely compatible with a possible earth impact only a few decades
hence. Had it not been for the "lucky accident" of the 1990
photographs, there would currently be justifiable reason for rather
widespread worry about the object, and reassurance would not be
possible until the start of what in popular culture is "the new
millennium". Imagine that!
Given the obsession of many NEO authorities with the calculation of
"probability" of impact (whether by a known or an unknown object), I was
a little surprised that the "p" word was completely missing from "The
Planetary Report" coverage. Sure, some of my dynamical-astronomy
colleagues have expressed an interest in the computation of a realistic
value for this probability. But how does one do it? Can one at all
conveniently attempt a computation of the probability, based on the
information at hand on March 11, that 1997 XF11 would hit the earth
during, say, the next half century? (Yes, the probability was small,
but that answer is insufficient.) I am told that state-of-the-art orbit
integrations on a modern computer can track the inner planets for 5
million years in one day. How many variants of the orbit of 1997 XF11
do we need to integrate in order to guarantee that "dangerous" cases
are not missed? Would 1 million be enough? If so, the complete
calculation for half a century would take ten days. O.K.: if that is
considered too long to wait for the orbit experts to come to a
"consensus" about the object's possible danger, we could go out and buy
nine more computers and work them hard for one day. But 1 million
orbits would allow only 10 possible values for each individual orbital
element. That does not sound very much, does it? Maybe we need 100
test values for each orbital element. That would indeed be some
But we can take a short cut, because we are forgetting the point
that the orbits must satisfy, in some appropriately non-Gaussian
manner, 95 observations covering a span of 88 days. There are
therefore some significant dependences among the various orbital
elements. Although this is not something that is normally considered
by dynamical astronomers who perform extensive numerical integrations
for qualitative studies of the solar system, it would perhaps not be
too difficult to set up these dependences and thereby simplify the
Once an appropriate procedure has been established, it would
presumably not be unreasonable routinely to perform such a 50-year
computation for all newly-discovered NEOs. Then, when unpleasant
surprises like 1997 XF11 crop up in the future, we can be ready for
them. I still think that it will be simpler, at least for the
kilometer-sized threats that interest NASA, to address the problem by
searching the archives for images at previous oppositions. In any case,
it is the observational approach that provides the more definitive
answer--generally completely eliminating (we hope) those occasional
troublesome cases like 1997 XF11.
(2) REEL SCIENCE: ASTEROIDS MAKE A BIG HIT
From the BOSTON GLOBE
By David L. Chandler, Globe Staff, 07/26/98
It has happened before. It will happen again. And, when it happens,
it's the most devastating kind of natural disaster - by a long shot -
that human beings face.
While the summer's blockbuster movies, ''Armageddon'' and ''Deep
Impact,'' explore the possibility that earth could be struck from above
with little warning, it is now becoming clear that this could be far
from just a theoretical risk. Our ancestors may have seen similar
(though less extreme) cataclysms firsthand.
New geological finds in Australia, for example, show that about 200
years ago large stretches of coastline were devastated by tsunamis that
towered hundreds of feet high and roared at least 20 miles inland; the
aborigines still relate vivid accounts of the event, which some
geologists say was almost certainly caused by an impact in the ocean -
just like the one depicted in ''Deep Impact.''
And some scientists now argue that historical events ranging from the
fall of Rome to the collapse of Babylon and Egypt's Old Kingdom may
also have been brought about - or helped along - by the crash of comet
fragments that could have triggered earthquakes and climatic shifts.
Until 1980, the idea that earth had suffered any significant effects
from impacts after life began was not taken seriously by most
scientists. But in that year, physicist Luis Alvarez and others
published a paper showing that the extinction of the dinosaurs 65
million years ago was caused by a huge cosmic impact. The idea, at
first greeted with skepticism, is now widely accepted. Now, scientists
are beginning to consider smaller but much more recent impacts.
Astronomers have begun to learn just how commonplace devastating
impacts have been in the history of the solar system, and now
scientists across a wide range of disciplines have begun to comb
through historical, archeological, geological, climatological, and
even mythological records from around the world in search of clues
about past bombardment of our planet. And they're striking pay dirt.
While proof is scarce, circumstantial evidence suggests that our planet
has suffered a long and terrifying history of cosmic pummeling.
That history, some researchers now think, is deeply ingrained in our
psyches and in our folk wisdom. It's no accident, they say, that the
very word for the worst kind of occurrences - disaster - means ''bad
Not that such claims are easily accepted. On the contrary, most
scientists remain deeply skeptical of any attempt to mine ancient
mythologies or oral histories for evidence of cosmic events. For many
astronomers, such efforts evoke too vividly the claims of writers such
as Immanuel Velikovsky, who insisted he had found evidence from such
ancient sources for a series of cataclysmic - and scientifically
impossible - cosmic encounters during human history.
As a result, the researchers who have been searching for evidence of
real cosmic impacts during the last few thousand years face a daunting
Peter Schultz, a geologist at Brown University who has been studying a
large-impact crater in Argentina that is about 5,000 years old, said in
an interview that the first person to make a convincing link between a
particular impact event and specific historical, archeological, or
mythological accounts will have to do so very convincingly to pass
muster with scientific colleagues.
''That first tie has to be so well tied, so irrefutable'' that
cause-and-effect ''has really got to get nailed,'' he said.
Schultz says he may be close to making such a connection with the
Argentine crater, called Rio Cuarto, by pinning down its date with
enough precision that it can be tied to specific accounts passed down
by the local people. But because he hopes to publish his evidence soon
in a major scientific journal, he would not reveal the details of the
links he found.
Astronomers know that impacts much smaller than the dinosaur killer 65
million years ago happen much more frequently, and that some of these
must have happened within historic times. For example, the explosion of
a comet fragment above the Siberian region of Tunguska in 1908 produced
effects that could be seen, heard, or felt for thousands of miles. If
that object had hit in a different place, it could have flattened a
major city. If it had struck the ocean, it might have devastated
hundreds of miles of coastline.
Events of that size, astronomers estimate, happen on average about once
every 100 or 200 years. A few dozen such impacts should have taken
place within human history, they say, and might have been so
destructive and astonishing that accounts of the cataclysm would have
been passed down through the generations and their imprints left in the
ground. The Australian tsunamis may be just such a case.
Such imprints don't necessarily include a crater, the most recognizable
sign of an impact. The Tunguska blast left none, having exploded about
20 miles above the ground. But sediments left by tsunamis, traces of
massive earthquakes or of unusually thick layers of dust kicked up by
the impact, may have left their telltale traces around the world.
Ted Bryant, a geologist at Wollongong University in Australia, has
found evidence of massive tsunamis all around Australia - even on
opposite coasts, regions that face different oceans and could not have
seen the effects of the same tsunamis. He is convinced that no other
known cause - no undersea earthquake or landslide - that could have
occurred in that region would have been sufficient to produce the
towering waves that the geological deposits reveal.
The evidence shows the waves reached heights of at least 200 feet, and
carried large boulders at least 20 miles inland. They apparently took
place a little more than 200 years ago - just before European settlers
first arrived on the continent.
''We think it must have been an impact slightly bigger'' than the
Tunguska blast, Bryant said.
And to account for the nearly simultaneous waves on both coasts, he
said, the likeliest candidate seems to be a comet that had split into
two or more pieces that struck in rapid succession - like the fragments
of Comet Shoemaker Levy 9 that hit Jupiter in 1994.
Remarkably, the local aborigines tell tales that describe such an event
in great detail, Bryant said. Most people had assumed that the stories
of a great white wave crashing from the sky and destroying their
civilization were allegories referring to the arrival of white
But now that it's clear that there really were waves so high that,
especially when they came crashing over a high hill, they would have
appeared to come from the sky.
Earlier events that may have been caused by comet impacts are even
harder to determine, but many scientists are working hard to establish
facts. W. Bruce Masse, an archeologist with the US Air Force and the
University of Hawaii, says he has accumulated evidence tying a major
impact in 2807 BC with a series of dramatic tsunamis and effects on
climate in South America. He hopes to publish the details of this
connection later this year in a scientific journal.
And several archeologists, including Benny Peiser of Liverpool John
Moore (sic) University in England, Harvey Weiss of Yale University, and
Marie-Agnes Courty of the French Center for Scientific Research, are
working hard to develop evidence that the widespread, sudden collapse
of Bronze Age civilizations around the world in about 2345 BC may have
been the result of a series of comet impacts, which caused a sudden
cooling of the climate, as well as tsunamis and earthquakes.
As a result, they say, civilizations that seemed to be in full flower,
including the Egyptian Old Kingdom, the Akkadian empire in Mesopotamia,
and the Hongshan culture in China, all declined suddenly and without
any trace of external cause such as a military attack.
That, too, according to a few astronomers, could have been the result
of multiple impacts from fragments of a comet that disintegrated from
coming too close to a planet or the sun. Victor Clube of Oxford
University and Bill Napier of the Armagh Observatory in Northern
Ireland have written extensively about their theory that a giant comet
- perhaps 60 miles across - broke apart thousands of years ago, and
that the earth periodically intersects streams of its debris - including
chunks large enough to strike with devastating effects.
''It's certainly worth looking'' for evidence of impacts in historic
times, said David Morrison, head of space research at the National
Aeronautics and Space Administration's Ames Research Center.
Morrison, author of a NASA study on the danger of impacts, adds that
''I'd be surprised'' if such evidence is found, because the actual rate
of impacts is much lower than suggested by astronomers like Clube and
But if they are right, he said, the evidence should be easy to find: If
the earth does intersect streams of debris that include objects large
enough to produce Tunguska-like blasts, then those objects would be
found by proposed searches for objects that might strike earth, such as
the Spaceguard survey recommended by his study. The answer should be
clear within a few years if such a study gets funded, he said.
In the meantime, a growing number of scientists are convinced that
looking at the records left by our ancestors - both the physical
evidence of archeological remains, as well as historical and
mythological accounts - could reveal important details about the cosmic
impacts the human race has had to deal with, and may even provide clues
to the degree of our future risk.
''Most mythology actually encodes celestial events,'' Masse said.
Though such research ''is just in its infancy,'' he said, it is
important to explore those sources, as well as the hard data of geology
and climatic records.
Doing so will help determine whether, as he believes, ''cosmic impacts
have been a major force in both cultural and biological evolution.''
This story ran on page A01 of the Boston Globe on 07/26/98.
© Copyright 1998 Globe Newspaper Company.
(3) MOVIE PRODUCERS CHALLENGED TO MATCH NEO GRANT
From Duncan Steel <firstname.lastname@example.org>
S P A C E V I E W S U P D A T E
Movie Producers Challenged to Match NEO Grant
Two private space organizations announced a $50,000 grant Wednesday,
July 1, to support work to locate and track near-Earth objects (NEOs),
and challenged the producers of two current Hollywood blockbusters to
match the grant.
The Space Frontier Founation (SFF) and the Foundation for the
International Non-Governmental Development of Space (FINDS) announced
the grant as a kickoff for a fundraising campaign to support NEO
research and bring together top experts on the issue.
The organizations also challenged the producers of the movies "Deep
Impact" and "Armageddon" -- two summer blockbusters that depict comets
and asteroids on collision courses with the Earth -- to match the
"The film industry has done an excellent job educating people about the
very real threat NEOs pose to our civilization, and is making millions
of dollars at the same time," said SFF president Rick Tumlinson.
""Meanwhile, there is very little money going to support the handful of
heroic people doing the actual work of finding and tracking these
potential Earth killers."
"There are astronomers who cannot afford to turn on their telescopes,"
Tumlinson noted. "Hollywood is making a lot of money playing off of
the fear -- now it's time for them to ante up."
The grant will go towards a program called "The Watch" whose goal is to
raise $1 million a year to support NEO research worldwide. The funds
will be disbursed by an advisory council headed by John Lewis of the
University of Arizona. The council will meet for the first time at an
SFF conference in California in October.
FINDS, a $13 million endowment that funds "breakthrough projects" in
space-related topics, currently supports NEO tracking projects at
Canada's University of Victoria and asteroid iron extraction work at
the University of Arizona.
Deep Impact, a movie released in May by Dreamworks and Paramount, cost
$75 million. The movie has grossed over $133 million in the United
States alone by late June. Armageddon, about a giant asteroid headed
towards Earth, opened in North America July 1. Its budget was
estimated at well over $100 million.
-- snip --
This has been the July 15, 1998, issue of SpaceViews Update. SpaceViews
Update is also availble on the World Wide web from the SpaceViews home
or via anonymous FTP from:
For editorial questions and article submissions for SpaceViews or
Spaceviews Update, contact the editor, Jeff Foust, at
email@example.com. For questions about the SpaceViews mailing list,
please contact firstname.lastname@example.org.
(4) NEW IMPLICATIONS FOR A TAURID METEOROID SWARM
D.J. Asher*) and K. Izumi: Meteor observations in Japan: New
implications for a Taurid meteoroid swarm. MONTHLY NOTICES OF THE
ROYAL ASTRONOMICAL SOCIETY, 1998, Vol.297, No.1, pp.23-27
*) COMMUN RES LABS, 893-1 HIRAI, KASHIMA, IBARAKI 3140012, JAPAN
Observational evidence is sought that the long-term (10(4) yr) action
of a mean motion resonance with Jupiter can produce structure in a
meteoroid stream, concentrating meteoroids in a dense swarm. More
specifically, predictions tabulated by Asher & Clube of enhanced
meteor and fireball activity from a Taurid Complex swarm in the 7:2
resonance are compared with observational data collected in Japan
over several decades. The swarm model was proposed for reasons
independent of the observations analysed here, and these newly
considered data are shown to be consistent with it. This allows
increased confidence in the Taurid swarm theory, and more generally
could mean that resonant trapping is a dynamical mechanism affecting
a significant amount of meteoroidal material in the inner Solar
(5) GREENLAND EXPEDITION
From Henrik Persson < email@example.com >
The meteorite search expedition left Copenhagen for Greenland on July
22nd and is now well under way. The Tycho Brahe Planetarium homepage
has news and images from the expedition. The information is sent home
each day via satelite link, however the English page is a day older
than the Danish.
Point your browser to http://www.astro.ku.dk/tycho/tbe98/english/ to
follow the events.
(6) MAGMA'S MAKEUP YIELDS NEW CLUES TO CATASTROPHIC ERUPTIONS
From Andrew Yee < firstname.lastname@example.org >
University of Rochester
Rochester, New York
CONTACT: Asish Basu (716) 275-2413 or Steve Bradt (716) 273-4726
July 22, 1998
MAGMA'S MAKEUP YIELDS NEW CLUES TO CATASTROPHIC ERUPTIONS
Despite the trove of summer blockbusters suggesting that the greatest
threats to humanity are asteroids lurking in outer space, scientists
now know that an equally great threat can lie roiling under our feet.
They've linked some of the greatest mass extinctions the world has ever
known with rock that originated near the Earth's core and crept upward,
lying in wait just beneath the surface before dousing the Earth with
Researchers at the University of Rochester and Harvard University have
now gained the clearest picture yet of the underpinnings of these most
catastrophic of eruptions by analyzing the chemical composition of lava
disgorged in one such massive period of volcanism in Siberia 250
million years ago. The findings by geochemists Asish Basu, Robyn
Hannigan, and Stein Jacobsen, published in a recent issue of
Geophysical Research Letters, indicate that the lava that erupted at
the time arose from the pristine lower mantle, material that harks back
to the birth of our solar system.
Scientists believe this particular volcanic outpouring played a role in
the greatest mass extinction the world has even seen. Up to 95 percent
of all plant and animal species were wiped out; a similar series of
eruptions 65 million years ago in India coincided precisely with the
sudden extinction of the dinosaurs.
The work plays into a long-running debate among geologists about the
floods of flaming rock that sporadically well up and burn through the
Earth's crust, oftentimes with disastrous consequences worldwide.
Scientists have long debated whether flood basalts, the vast expanses
of rock that result from such volcanic outpourings, have their origins
in rumblings deep within the Earth or closer to its surface. Now, by
studying the lava's major chemical components, such as sodium,
magnesium, and iron, as well as rare isotopes of neodymium, strontium,
lead, and helium, Basu and Jacobsen have found that the Siberian flood
basalt's chemical composition matches that of magma found deep within
"This indicates beyond any doubt that the lava that's now hardened into
the Siberian flood basalt originated far beneath the Earth's surface,
between the lower mantle and the molten iron core," says Basu, a
professor of earth and environmental sciences at Rochester.
The work, funded by the National Science Foundation, is the latest in a
series of findings by Basu and other geologists that point to the lower
mantle as the source of such volcanism in Siberia and other parts of
the world. Three years ago in the journal Science, Basu and colleagues
suggested that the presence of an unusual concentration of helium-3, an
ancient gas common deep within the Earth, could serve to trace the
Siberian flood basalt's lineage to the lower mantle.
"Members of the opposing school, which held that the flood basalts
arose from the melting of lithospheric rock right under the Earth's
crust, weren't persuaded by those results," says Jacobsen, a Harvard
professor of geochemistry who joined Basu and Hannigan, a former
Rochester doctoral student, in the more recent research. "These
geochemists said that while it was possible that a portion of the rock
came from deep within the Earth, the majority of the rock probably
wasn't formed that way. They discounted the helium-3, suggesting that
it may have been recycled from cosmic dust falling to Earth and making
its way into the rocks."
Jacobsen and Basu say the current research, which examined the
distribution of more than a half-dozen chemical elements and rare
isotopes found throughout the basalts, should put those theories to
rest. The team analyzed rocks culled from the Siberian flood basalt for
compounds that are rare on the Earth's surface but common in parts of
the lower mantle that originated soon after the birth of our solar
system. They also drew upon experiments conducted at other institutions
where researchers melted rocks in the lab, much as happens deep within
the Earth's interior. They found that the Siberian flood basalt arose
from super-heated, buoyant rock that rose in a narrow column from a
depth of 1,800 miles into a huge mushroom-shaped mass of hot rock just
40 to 50 miles below present-day Siberia. Then, some 250 million years
ago, 12 to 16 percent of this rock suddenly melted and broke through
the Earth's crust, resulting in a vast flood of lava.
"It is surprising that most of this melting occurred so close to the
Earth's surface, really just beneath the crust," Jacobsen says. While
it's easy to envision rocks melting in the massive crucible at the
Earth's core, the lava that spilled into Siberia 250 million years ago
melted at the much lower temperatures and pressures found just beneath
the surface. Basu says it's an example of decompressional melting,
where a large decrease in pressure can actually depress the melting
point of a substance.
These overwhelming periods of flood basalt volcanism make ordinary
volcanoes look like child's play, releasing up to a million times the
material belched out by an eruption such as that of Mount St. Helens.
In fact, the one million cubic kilometers of molten volcanic rock that
bubbled up to the surface -- now a Siberian plateau the size of
California -- would be enough lava to cover the entire Earth to a depth
of 10 feet. "This was, almost unquestionably, the most catastrophic
volcanism in last half-billion years of the Earth's history," Basu
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