CCNet 30/2002 - 4 March 2002

"My real worry is that too many people will get frantic about the
impact hazard. ... I actually think we're doing about as much as we
--Alan Harris, 27 February 2002

"Mega-tsunamis have happened with greater frequency than modern
science would like to believe, and no coastline in the world is safe, says
Canadian geologist-geographer Edward Bryant.... Bryant's suspicions of
meteor and comet impacts a relatively short time ago rile many in the
scientific community who believe the chances of Earth colliding with space
debris are tiny. But Bryant says computer modelling suggests a meteor would
not have to be a "dinosaur killer" to cause a mega-tsunami. A chunk 100
metres in diameter moving at 20 metres per second could
theoretically produce a tsunami that is 27 metres high at source."
--Michael Christie, Reuters, 26 February, 2002

Reuters, 26 February, 2002

EurekAlert, 28 February 2002

Scientific American, March 2002

Sky & Telescope, 26 February 2002

Ron Baalke < >

Asahi Shimbun, 28 February 2002

Charles Cockell < >

Duncan Steel < >

Jon Richfield < >

Michael Paine

David James Johnson < >

The Times Record, 27 February 2002


>From Reuters, 26 February, 2002

By Michael Christie

WOLLONGONG, Australia (Reuters) - One day, a giant wave travelling at 200
kph (124 mph) across open water could crash into Sydney harbour, wipe out
the beaches of California or plough across the golf courses of northeast

Mega-tsunamis have happened with greater frequency than modern science would
like to believe, and no coastline in the world is safe, says Canadian
geologist-geographer Edward Bryant.

He said he had found signs of giant waves sweeping over 130 metre (425 ft)
high headlands in southeast Australia, roaring down the U.S. West Coast and
carving into the bedrock of the Scottish coastline north of Edinburgh.

"I believe St Andrews golf course is a tsunami deposit," Bryant, head of
geosciences at Wollongong University south of Sydney, told Reuters.

Over the past 2,000 years, tsunamis have officially killed 462,597 people in
the Pacific region alone, with the largest toll recorded in the Japanese

Of the top recorded events, the Lisbon earthquake of 1755 is said to have
triggered a 15-metre high wave that destroyed the port of Lisbon and caused
widespread destruction in southwest Spain, western Morocco and across the
Atlantic in the Caribbean.

Modern science blames the killer waves on earthquakes and most countries
believe they are immune.

But in his book, "Tsunamis - The Underrated Hazard", Bryant argues that
submarine landslides, underwater volcanoes and even the potentially
catastrophic scenario of a meteorite impact must also be taken into account
when evaluating tsunami risk.

That means a destructive tsunami moving at 250 metres per second in deep
water, 85 metres per second across continental shelves and at 10 metres per
second at shore could strike an unprotected coastal metropolis anywhere,
killing thousands.


In 1989, Bryant was dabbling into the coastal evolution of rock platforms
and sand barriers along the New South Wales coastline of eastern Australia
when he noticed something strange.

Giant boulders, some the size of boxcars and weighing almost 100 tonnes,
were jammed 33 metres above sea level into a crevice at the top of a rock
platform sheltered from storm waves.

Further field work found gravel dunes on a 130-metre-high headland and other
massive boulders more than 100 metres inland. Bryant then examined bedrock
that had been savagely eroded and found that headlands carved into inverted
tootbrushes, where a gap had been roughly gouged in the middle, existed from
Cairns in the far northeast to Victoria state in the south.

This could not be explained by normal wave action or storms.

"But a tsunami could do this," Bryant said.

"From being a trendy process geomorphologist wrapped in the ambience of the
1960s, I had descended into the abyss of catastrophism," Bryant writes in
his book.

Similar toothbrush headlands exist in northeast Scotland and gravel has been
dumped up to 30 km inland in Western Australia.

To the scorn of many modern scientists, Bryant says it is "naive" to base
what we know about tsunamis simply on documented history.

In North America and Australia, official history only goes back as far as
white colonisation. We may be ignoring the legends of the Indians of North
America, the Aborigines of Australia or the Maoris of New Zealand at our
peril, he said.


"We ignore all oral record and it's probably a significant oversight,"
Bryant told Reuters.

One Aboriginal tale tells how one of the four pillars holding up the sky
collapsed in the east and the sea also fell in.

The Maoris of New Zealand have long spoken of a time of fire that burned the
land to a crisp.

A legend told by the Kwenaitchechat people of the U.S. Pacific Northwest
tells of a great shaking of the earth that led to the sea receding and then
coming back in a great wall.

Using dating techniques, Bryant argues there is evidence that eastern
Australia was struck by a mega-tsunami around 1500, which would coincide
with the Aboriginal tale of a "great white wave".

The Aboriginal accounts of fire in the sky mean a comet crashing into the
South Tasman Sea could have been responsible.

Carbon dating indicates a great fire ravaged New Zealand at the same time,
giving further weight to the theory of a comet.

And Bryant said Japanese researchers probing past tsunamis had found
evidence of a massive earthquake off Oregon in January 1700 that would
coincide with the Indian tales, and with a Pacific seismic zone where the
Juan de Fuca tectonic plate grinds under the North American plate in a
process called subduction.

"We now know the Oregon subduction zone goes every 300 years. 1700...2002?"
he wonders with raised eyebrows.

Bryant's suspicions of meteor and comet impacts a relatively short time ago
rile many in the scientific community who believe the chances of Earth
colliding with space debris are tiny.

But Bryant says computer modelling suggests a meteor would not have to be a
"dinosaur killer" to cause a mega-tsunami. A chunk 100 metres in diameter
moving at 20 metres per second could theoretically produce a tsunami that is
27 metres high at source.


Focusing on extreme scenarios such as meteorite impacts may also
underestimate the risk of a mega-tsunami.

Contentiously, Bryant argues that underwater landslides, which can involve
thousands of cubic km (miles) of material, may have the power alone to
generate the giant waves.

A 1998 earthquake off northwest Papua New Guinea has been blamed for a
tsunami that killed around 2,000 people near Aitape.

But according to conventional scientific wisdom, the 7.1 magnitude was too
small to be responsible for the 15-metre wave that at some points swept 500
metres inland.

Bryant says a submarine landslide was the likely villain.

Another landslide-induced tsunami may have been responsible for shaping the
Scottish coastline, including the dunes of St Andrews, 7,000 years ago.

Scientists have found indications of a large submarine landslide at Storegga
off the east coast of Norway that Bryant says could have sent a wave
originally measuring 8-12 metres roaring into the North Sea and across the

Worryingly, he says geologists at the University of Sydney have recently
mapped around 170 submarine landslide zones off Sydney, Australia's largest
city with four million inhabitants.

What's more, he has found signs that tsunamis have struck the New South
Wales coast with alarming regularity every 500 years.

If you take the risk seriously, it does not take much to save human life
from tsunamis.

Chile, Japan and Hawaii already have warning systems and evacuation drills.
Seabed sensors can send tsunami warnings via satellite triggering bells,
alarms and telephones within minutes.

"The only guarantee or prediction is that they will happen again, sometime
soon, on a coastline near you," Bryant concludes.

"Tsunami are very much an underrated, widespread hazard. Any coast is at

Copyright 2002, Reuters


>From EurekAlert, 28 February 2002

Public release date: 28-Feb-2002

Contact: Harvey Leifert
American Geophysical Union

Cataclysm 3.9 billion years ago was caused by asteroids, not comets,
researchers say

WASHINGTON - The bombardment that resurfaced the Earth 3.9 billion years ago
was produced by asteroids, not comets, according to David Kring of the
University of Arizona Lunar and Planetary Laboratory and Barbara Cohen,
formerly at the UA and now with the University of Hawaii. Their findings
appear today in the Journal of Geophysical Research - Planets, published by
the American Geophysical Union.

The significance of this conclusion is that the bombardment was so severe
that it destroyed older rocks on Earth. This, Kring says, is the reason that
the oldest rocks ever found are less than 3.9 billion years old.

Additionally, the researchers argue, hydrothermal systems generated by the
impacts would have been excellent incubators for pre-biotic chemistry and
the early evolution of life, consistent with previous work that suggests
life originated in hot water systems around 3.85 billion years ago.

This same bombardment, according to Kring and Cohen, affected the entire
inner solar system, producing thousands of impact craters on Mercury, Venus,
the Moon and Mars. Most of the craters in the southern hemisphere of Mars
were produced during this event.

On Earth, at least 22,000 impact craters with diameters greater than 20
kilometers [12 miles] were produced, including about 40 impact basins with
diameters of about 1,000 kilometers [600 miles] in diameter. Several impact
craters of about 5,000 kilometers [3,000 miles] were created, as well, each
one exceeding the dimensions of Australia, Europe, Antarctica or South
America. The thousands of impacts occurred in a very short period of time,
potentially producing globally significant environmental change at an
average rate of once per 100 years.

Also, the event is recorded in the asteroid belt between Mars and Jupiter,
as witnessed by the meteoritic fragments that have survived to fall to Earth
today, the authors say.

Kring has been involved in the research and measurements of the Chicxulub
impact crater located near Merida, Yucatan, Mexico. He has collaborated and
led various international research teams which have drilled to unearth
evidence of the Cretaceous-Tertiary (K/T) impact which is thought to have
led to mass extinctions on Earth, including that of the dinosaurs. Earlier
this month, he returned from a drilling operation at the impact site where
crews worked around the clock to recover core samples in an effort to
determine what caused the impact and other details of the catastrophic event
that wiped out more than 75 percent of all plant and animal species on

The research leading to this paper was partially supported by a grant from


>From Scientific American, March 2002

by Luann Becker

Did extraterrestrial collisions capable of causing widespread extinctions
pound the earth not once, but twice- or even several times?

Most people are unaware of it, but our planet is under a constant barrage by
the cosmos. Our galactic neighborhood is littered with comets, asteroids and
other debris left over from the birth of the solar system. Most of the space
detritus that strikes the earth is interplanetary dust, but a few of these
cosmic projectiles have measured five kilo-meters (about 3.1 miles) or more
across. Based on the number of craters on the moon, astronomers estimate
that about 60 such giant space rocks slammed into the earth during the past
600 million years. Even the smallest of those collisions would have left a
scar 95 kilometers (about 60 miles) wide and would have released a blast of
kinetic energy equivalent to detonating 10 million megatons of TNT.

Such massive impacts are no doubt capable of triggering drastic and abrupt
changes to the planet and its inhabitants. Indeed, over the same time period
the fossil record reveals five great biological crises in which, on average,
more than half of all living species ceased to exist.
After a period of heated con-troversy, scientists began to accept that an
asteroid impact precipitated one of these catastrophes: the demise of the
dinosaurs 65 million years ago. With that one exception, however, compelling
evidence for large impacts coincident with severe mass extinctions remained
elusive-until recently.

During the past two years, researchers have discovered new methods for
assessing where and when impacts occurred, and the evidence connecting them
to other widespread die-offs is getting stronger. New tracers of impacts are
cropping up, for instance, in rocks laid down at the end of the Permian
period- the time 250 million years ago when a mysterious event known as the
Great Dying wiped out 90 percent of the planet's species.

Evidence for impacts associated with other extinctions is tenuous but
growing stronger as well. Scientists find such hints of multiple
life-altering impacts in a variety of forms. Craters and shattered or
shocked rocks-the best evidence of an ancient impact-are turning up at key
time intervals that suggest a link with extinction. But more often than not,
this kind of physical evidence is buried under thick layers of sediment or
is obscured by erosion. Researchers now understand that the biggest blows
also leave other direct, as well as indirect, clues hidden in the rock
record. The first direct tracers included tiny mineral crystals that had
been fractured or melted by the blast. Also found in fallout layers have
been elements known to form in space but not on the earth. Indeed, my
colleagues and I have discovered extraterrestrial gases trapped inside
carbon molecules called fullerenes in several suspected impact-related
sediments and craters.

Equally intriguing are the indirect tracers that paleontologists have
recognized: rapid die-offs of terrestrial vegetation and abrupt declines in
the productivity of marine organisms coincident with at least three of the
five great extinctions. Such severe and rapid perturbations in the earth's
ecosystem are rare, and some scientists suspect that only a catastrophe as
abrupt as an impact could trigger them.

Dinosaur Killer

THE FIRST IMPACT TRACER linked to a severe mass extinction was an unearthly
concentration of iridium, an element that is rare in rocks on our planet's
surface but abundant in many meteorites. In 1980 a team from the University
of California at Berkeley-led by Nobel Prize-winning physicist Luis Alvarez
and his son, geologist Walter Alvarez-reported a surprisingly high
concentration of this element within a centimeter-thick layer of clay
exposed near Gubbio, Italy. The Berkeley team calculated that the average
daily delivery of cosmic dust could not account for the amount of iridium it
measured. Based on these findings, the scientists hypothesized that it was
fallout from a blast created when an asteroid, some 10 to 14 kilometers (six
to nine miles) across, collided with the earth.

Even more fascinating, the clay layer had been dated to 65 million years
ago, the end of the Cretaceous period. From this iridium discovery came the
landmark hypothesis that a giant impact ended the reign of the dinosaurs-and
that such events may well be associated with other severe mass extinctions
over the past 600 million years. Twenty years ago this bold and sweeping
claim stunned scientists, most of whom had been content to assume that the
dinosaur extinction was a gradual process initiated by a contemporaneous
increase in global volcanic activity. The announcement led to intense
debates and reexaminations of end Cretaceous rocks around the world.

Out of this scrutiny emerged three additional impact tracers: dramatic
disfigurations of the earthly rocks and plant life in the form of
microspherules, shocked quartz and high concentrations of soot. In 1981 Jan
Smit, now at the Free University in Amsterdam, uncovered microscopic
droplets of glass, called microspherules, which he argued were products of
the rapid cooling of molten rock that splashed into the atmosphere during
the impact. Three years later Bruce Bohor and his colleagues at the U.S.
Geological Survey were among the first researchers to explain the formation
of shocked quartz. Few earthly circumstances have the power to disfigure
quartz, which is a highly stable mineral even at high temperatures and
pressures deep inside the earth's crust.

At the time microspherules and shocked quartz were introduced as impact
tracers, some still attributed them to extreme volcanic activity. Powerful
eruptions can indeed fracture quartz grains-but only in one direction, not
in the multiple directions displayed in Bohor's samples. The microspherules
contained trace elements that were markedly distinct from those formed in
volcanic blasts. Scientists subsequently found enhanced iridium levels at
more than 100 end Cretaceous sites worldwide and shocked quartz at more than
30 sites.

Least contentious of the four primary impact tracers to come out of the
1980s were soot and ash, which measured tens of thousands of times higher
than normal levels, from impact-triggered fires. The most convincing
evidence to support the impact scenario, however, was the recognition of the
crater itself, known today as Chicxulub, in Yucatán, Mexico. Shortly after
the Alvarez announcement in 1980, geophysicists Tony Camargo and Glen
Penfield of the Mexican national oil company, PEMEX, reported an immense
circular pattern-later estimated to be some 180 kilometers (about 110 miles)
across-while surveying for new oil and gas prospects buried in the Gulf of

Other researchers confirmed the crater's existence in 1991. Finding a
reasonable candidate for an impact crater marked a turning point in the
search for the causes of extreme climate perturbations and mass
extinctions-away from earthly sources such as volcanism and toward a
singular, catastrophic event. Both volcanoes and impacts eject enormous
quantities of toxic pollutants such as ash, sulfur and carbon dioxide into
the atmosphere, triggering severe climate change and environmental
degradation. The difference is in the timing. The instantaneous release from
an impact would potentially kill off species in a few thousand years.
Massive volcanism, on the other hand, continues to release its pollutants
over millions of years, drawing out its effects on life and its habitats.

see ]

While geologists were searching for craters and other impact tracers,
paleontologists were adding their own momentum to the impact scenario.
Fossil experts had long been inclined to agree with the volcanism theory
because the disappearance of species in the fossil record appeared to be
gradual. A convincing counterargument came from paleontologists Philip
Signor of the University of California at Davis and Jere Lipps, now at
Berkeley. In 1982 they recognized that the typical approach for defining the
last occurrence of a given species did not take into account the
incompleteness of the fossil record or the biases introduced in the way the
fossils were collected.

Many researchers subsequently conducted high-resolution studies of multiple
species. These statistically more reliable assessments indicate that the
actual extinction time periods at the end of the Cretaceous-and at the end
of the Permian-were abrupt (thousands of years) rather than gradual
(millions of years). Although volcanically induced climate change no doubt
contributed to the demise of some species, life was well on its way to
recovery before the volcanism ceased-making the case for an impact trigger
more compelling.

Extraterrestrial Hitchhikers

THE RECOGNITION of a shorter time frame for the Great Dying prompted several
scientists to search for associated impact tracers and craters. By the early
1990s scientific papers were citing evidence of iridium and shocked quartz
from end Permian rocks; however, the reported concentrations were 10-to
100-fold lower than those in the end Cretaceous clay. This finding prompted
some paleontologists to claim that the impact that marked the end of the age
of dinosaurs was as singular and unique as the animals themselves.

Other scientists reasoned that perhaps an impact had occurred but the rocks
simply did not preserve the same clues that were so obvious in end
Cretaceous samples. At the end of the Permian period the earth's landmasses
were configured into one supercontinent, Pangea, and a superocean,
Panthalassa. An asteroid or comet that hit the deep ocean would not generate
shocked quartz, because quartz is rare in ocean crust. Nor would it
necessarily lead to the spread of iridium worldwide, because
not as much debris would be ejected into the atmosphere. Supporting an
ocean-impact hypothesis for more ancient extinctions such as the Great
Dying, it turned out, would require new tracers.

One of the next impact tracers to hit the scene-and one that would
eventually turn up in meteorites and at least two impact craters-evolved out
of the accidental discovery of a new form of carbon. In the second year of
my doctoral studies at the Scripps Institution of Oceanography in La Jolla,
Calif., my adviser, geochemist Jeffrey Bada, showed me an article that had
appeared in a recent issue of Scientific American [see "Fullerenes," by
Robert F. Curl and Richard E. Smalley; October 1991]. It outlined the
discovery of a new form of carbon, closed-cage structures called fullerenes
(also referred to as buckminsterfullerenes or "buckyballs," after the
inventor of the geodesic domes that they resemble). A group of astrochemists
and physical chemists had inadvertently created fullerenes in 1985 during
laboratory experiments designed to mimic the formation of carbon clusters,
or stardust, in some stars. Additional experiments revealed that fullerenes,
unlike the other solid forms of carbon, diamond and graphite, were soluble
in some organic solvents, a property that would prove their existence and
lead to a Nobel Prize in Chemistry for Curl, Smalley and Harold W. Kroto in

Knowing that stardust, like iridium, is delivered to our planet in the form
of cosmic dust, asteroids and comets, we decided to search for these exotic
carbon molecules in earthly sedi-ments. We chose a known impact site-the
1.85-billion-year-old Sudbury crater in Ontario, Canada-because of its
unique lining of carbon-rich breccia, a mixture of shattered target rocks
and other fallout from the blast. (Not unlike the Chicxulub con-troversy, it
took the discovery of shocked quartz and shatter-cones, features described
as shock waves captured in the rock, to convince most scientists that the
crater was an impact scar rather than volcanic in origin.)

Because fullerene is a pure-carbon molecule, the Sudbury breccia offered a
prime location for collecting promising samples, which we did in 1993. By
exploiting the unique solubility properties of fullerene, I was able to
isolate the most stable molecules-those built from 60 or 70 carbon atoms
each-in the laboratory. The next critical questions were: Did the fullerenes
hitch a ride to the earth on the impactor, surviving the catastrophic blast?
Or were they somehow generated in the intense heat and pressures of the

Meanwhile organic chemist Martin Saunders and his colleagues at Yale
University and geochemist Robert Poreda of the University of Rochester were
discovering a way to resolve this question. In 1993 Saunders and Poreda
demonstrated that fullerenes have the unusual ability to capture noble
gases-such as helium, neon and argon-within their caged structures. As soon
as Bada and I became aware of this discovery, in 1994, we asked Poreda to
examine our Sudbury fullerenes. We knew that the isotopic compositions of
noble gases observed in space (like those measured in meteorites and cosmic
dust) were clearly distinct from those found on the earth. That meant we had
a simple way to test where our exotic carbon originated: measure the
isotopic signatures of the gases within them.

What we found astounds us to this day. The Sudbury fullerenes contained
helium with compositions similar to some meteorites and cosmic dust. We
reasoned that the molecules must have survived the catastrophic impact, but
how? Geologists agree that the Sudbury impactor was at least eight
kilometers (about five miles) across. Computer simulations predicted that
all organic compounds in an asteroid or comet of this size would be
vaporized on impact. Perhaps even more troubling was the initial lack of
compelling evidence for fullerenes in meteorites. We, too, were surprised
that the fullerenes survived. But as for their apparent absence in
meteorites, we suspected that previous workers had not looked for all the
known types. In the original experiment designed to simulate stardust, a
family of large fullerenes formed in addition to the 60- and 70-atom
molecules. Indeed, on a whim, I attempted to isolate larger fullerenes in
some carbon-rich meteorites, and a whole series of cages with up to 400
carbon atoms were present. Like their smaller counterparts from the Sudbury
crater, these larger structures contained extraterrestrial helium, neon and

With the discovery of the giant fullerenes in meteorites, Poreda and I
decided to test our new method on sediments associated with mass
extinctions. We first revisited fullerene samples that other researchers had
discovered at end Cretaceous had proposed that the exotic carbon was part of
the soot that accumulated in the wake of the massive, impact-ignited fires.
The heat of such a fire may have been intense enough to transform plant
carbon into fullerenes, but it could not account for the extraterrestrial
helium that we found inside them.

Inspired by this success, we wondered whether fullerenes would be a reliable
tracer of large impacts elsewhere in the fossil record. Sediments associated
with the Great Dying became our next focus. In February 2001 we reported
extraterrestrial helium and argon in fullerenes from end Permian locations
in China and Japan. In the past several months we have also begun to look at
end Permian sites in Antarctica. Preliminary investigations of samples from
Graphite Peak indicate that fullerenes are present and contain
extraterrestrial helium and argon.

These end Permian fullerenes are also associated with shocked quartz,
another direct indicator of impact.

As exciting as these new impact tracers linked to the Great Dying have been,
it would be misleading to suggest that fullerenes are the smoking gun for a
giant impact. Many scientists still argue that volcanism is the more likely
cause. Some have suggested that cosmic dust is a better indicator of an
impact event than fullerenes are. Others are asking why evidence such as
shocked quartz and iridium are so rare in rocks associated with the Great
Dying and will remain skeptical if an impact crater cannot be found.

Forging Ahead

UNDAUNTED BY SKEPTICISM, a handful of scientists continues to look for
potential impact craters and tracers. Recently geologist John Gorter of Agip
Petroleum in Perth, Australia, described a potential, enormous end Permian
impact crater buried under a thick pile of sediments offshore of
northwestern Australia. Gorter interpreted a seismic line over the region
that suggests a circular structure, called the Bedout, some 200 kilo-meters
(about 125 miles) across. If a future discovery of shocked quartz or other
impact tracers proves this structure to be ground zero for a life-altering
impact, its location could ex-plain why extraterrestrial fullerenes are
found in China, Japan and Antarctica-regions close to the proposed
impact-but not in more distant sites, such as Hungary and Israel.

Also encouraging are the recent discoveries of other tracers proposed as
direct products of an impact. In September 2001 geochemist Kunio Kaiho of
Tohoku University in Japan and his colleagues reported the presence of
impact-metamorphosed iron-silica-nickel grains in the same end Permian rocks
in Meishan, China, where evidence for abrupt extinctions and
extraterres-trial fullerenes has cropped up. Such grains have been reported
. In the absence of craters or other direct evidence, it still may be
possible to determine the occurrence of an impact by noting
symptoms of rapid environmental or biological changes. In 2000, in fact,
Peter Ward of the University of Washington and his colleagues reported
evidence of abrupt die-offs of rooted plants in end Permian rocks of the
Karoo Basin in South Africa.

Several groups have also described a sharp drop in productivity in marine
species associated with the Great Dying-and with the third of the five big
mass extinctions, in some 200-million-year-old end Triassic rocks. These
productivity crashes, marked by a shift in the values of carbon isotopes,
correlate to a similar record at the end of the Cretaceous, a time when few
scientists doubt a violent impact occurred.

Only more careful investigation will determine if new impact tracers-both
direct products of a collision and indirect evidence for abrupt ecological
change-will prove themselves reliable in the long run. So far researchers
have demonstrated that several lines of evidence for impacts are present in
rocks that record three of our planet's five most devastating biological
crises. For the two other largest extinctions-one about 440 million years
ago and the other about 365 million years ago-iridium, shocked quartz,
microspherules, potential craters and productivity collapse have been
reported, but the causal link between impact and extinction is still tenuous
at best. It is important to note, however, that the impact tracers that
typify the end of the Cretaceous will not be as robust in rocks linked to
older mass extinctions.

The idea that giant collisions may have occurred multiple times is
intriguing in its own right. But perhaps even more compelling is the growing
indication that these destructive events may be necessary to promote
evolutionary change. Most paleontologists believe that the Great Dying, for
instance, enabled dinosaurs to thrive by opening niches previously occupied
by other animals. Likewise, the demise of the dinosaurs allowed mammals to
flourish. Whatever stimulated these mass extinctions, then, also made
possible our own existence. As researchers continue to detect impact tracers
around the world, it's looking more like impacts are the culprits of the
greatest unresolved murder mysteries in the history of life on earth.

More to explore

Impact Event at the Permian-Triassic Boundary: Evidence from
Extraterrestrial Noble Gases in Fullerene. Luann Becker, Robert J. Poreda,
Andrew G. Hunt, Theodore E. Bunch and Michael Rampino in Science, Vol. 291,
pages 1530-1533; February 23, 2001.

Accretion of Extraterrestrial Matter throughout Earth's History. Edited by
Bernhard Peucker-Ehrenbrink and Birger Schmitz. Kluwer Academic/Plenum
Publishers, 2001.

LUANN BECKER has studied impact tracers since she began her career as a
geochemist at the Scripps Institution of Oceanography in La Rolla, Calif.,in
1990.In 1998 Becker participated in a meteorite-collecting expedition in
Antarctica and in July 2001 was awarded the National Science Foundation
Antarctic Service Medal. The following month she joined the faculty at the
University of California, Santa Barbara, where she continues to study
fullerenes and exotic gases trapped within them as impact tracers. This
summer she and her colleagues will conduct fieldwork at end Permian
extinction sites in South Africa and Australia. Part of this expedition will
be included in a television documentary, scheduled to air this fall, about
mass extinctions and their causes.

c2002 Scientific American


>From Sky & Telescope, 26 February 2002

By J. Kelly Beatty

February 25, 2002 | It's been 11 years since geologists pinpointed the
location of a huge impact that, most of them believe, led to the demise of
the dinosaurs. The crater lies at the tip of the Yucatán Peninsula, centered
on a coastal village named Chicxulub Puerto. There, 65 million years ago, a
chunk of asteroid or comet roughly 10 kilometers across slammed into Earth
and gouged out a hole at least 180 kilometers (115 miles) across. Evidence
of this catastrophic event has turned up worldwide, even in Antarctica.

However, identifying the crater and getting at it are two very different
things. Today the Chicxulub site lies completely buried under 1,000 meters
of limestone sediment. Initially, impact specialists thought they'd caught a
fortuitous break with the realization that Pemex, the Mexican national oil
company, had drilled a series of deep exploratory wells in the region
beginning in 1951. But calamity struck in 1979, when a warehouse fire
destroyed all but a few fragments of the extracted-rock well cores.

For the last three months, the grinding whir of drilling once again echoed
over the region's scrubby jungle. The new effort, located on the Yaxcopoil
hacienda about 40 km southwest of provincial capital of Mérida, began
optimistically on December 3rd with the hope of reaching a
depth of at least 1,800 meters (5,900 feet). By mid-January the scientists
were buoyed with some good news: the drill had punched through 800 meters of
overlying limestone and into suevite, a fragmented mixture of target rock
and quenched blobs ejected by the impact.

But on January 20th, "we had a bad day," reports Burkhard Dressler (Humboldt
University, Berlin), who supervised the drilling and core recovery. The
drill bit became hopelessly stuck, idling the project for nearly three
weeks. Work resumed 'round-the-clock on February 7th, but with the cost
capped at $1.5 million, precious time had been lost. The final core came up
late on the 23rd, from a depth of 1,510 meters. "At the furious daily pace
they [were] drilling," observes participant David A. Kring (University of
Arizona), "we could have potentially reached 2.5 km if the drill did not get

Although pleased with the results, the project's scientists would have liked
to get their hands on more of the impact-related layers near the crater's
floor (the suevite proved only temporary, and the drilling continued through
limestone and sulfate-rich anyhydrite sediments until the end). "Although
the units are thinner than we would have liked, they look spectacular,"
Kring notes. He explains that choosing the Yaxcopoil site represented a
compromise, because the team feared it would not reach the rock under "melt
sheet" closer to the crater's center. In the end, the melt sheet itself
eluded the effort anyway.

Still, Kring says, "We are getting the best core ever obtained of the target
lithologies. Consequently, we will be able to extract additional information
about the CO2 and sulphate aerosols that affected the post-impact
environment." With the Yaxcopoil-1 hole capped, says Dressler, "We are in a
packing and wrapping-up mode right now." The effort's focus will now turn to
the Autonomous National University of Mexico (UNAM) in Mexico City, where
the carefully extracted cores will be housed and analyzed.

Copyright 2002 Sky Publishing Corp.


>From Ron Baalke < >

--- X-rays and reflected light suggest that asteroid 433 Eros is similar in
composition to the most common type of meteorite--maybe.

Written by G. Jeffrey Taylor
Hawaii Institute of Geophysics and Planetology
February 26, 2002

The Near-Earth Asteroid Rendezvous (NEAR) mission spent about a year
orbiting the asteroid 433 Eros, a 33 x 13 x 13 km chunk of rock. The main
goal of the mission was to determine the chemical and mineral make up of the
asteroid and to try to settle an argument about the nature of

S-asteroids are a somewhat diverse group of little planets with similar
characteristics in the spectra of light reflected from them. The consensus
was that they are mixtures of iron-magnesium silicates with some metallic
iron, but that is where the agreement ended. Some scientists argued that
S-asteroids are like ordinary chondrite meteorites, which are unmelted rocks
left over from when the solar system formed. Others argued just as
vigorously that S-asteroids are differentiated objects, little worlds that
were melted soon after they formed. Using measurements of x-rays emitted
from the asteroid and light reflected off it, the consensus is that Eros is
more like an ordinary chondrite than any other type, though a little bit of
melting cannot be ruled out. This measurement of one S-asteroid, however,
has not settled the argument. More asteroids need to be visited and samples
returned from them.


Clark, Beth E. and 11 others (2001) Space weathering on Eros: Constraints
from albedo and spectral measurements of Psyche crater. Meteoritics and
Planetary Science, vol. 36, p. 1617-1637.

McCoy, Timothy J. and 16 others (2001) The composition of 433 Eros: A
mineralogical-chemical synthesis. Meteoritics and Planetary Science, vol.
36, p. 1661-1672.

Nittler, Larry R. and 14 others (2001) X-ray fluorescence measurements of
the surface elemental composition of asteroid 433 Eros. Meteoritics and
Planetary Science, vol. 36, p. 1673-1695.

McFadden, Lucy A. and 7 others (2001) Mineralogical interpretation of
reflectance spectra of Eros from NEAR near-infrared spectrometer low phase
flyby. Meteoritics and Planetary Science, vol. 36, p. 1711-1726.

Full story here:


The Asahi Shimbun, 28 February 2002

A newly detected comet approaching the solar system may be one that last
appeared 470 years ago, according to the calculations of an amateur
astronomer in Hyogo Prefecture.

The comet was spotted Feb. 1 by Kaoyu Ikeya of Shizuoka Prefecture and Zhang
Daqin of China. It is expected to come nearest to Earth in late March. It
will be visible to the naked eye.

But Syuichi Nakano of Sumoto, Hyogo Prefecture, said in a report to the
International Astronomical Union that Comet Ikeya-Zhang may not be so new a
discovery. The amateur astronomer said the comet was on a similar orbit to
that of one that approached Earth around September 1532.

According to the National Astronomical Observatory of Japan, the appearance
of the 1532 celestial body was recorded among accounts of 16th-century
events in 18th-century books from both China and the Korean Peninsula.

In Japan, Myohoji-ki and other records from the age of warring states, in
the 16th century, referred to the approaching object.

Yet another theory suggests it may be a comet last seen in 1661.

There have been cases in which comets return after decades, but the
discovery of one coming back after 300 to 500 years is very rare, according
to Junichi Watanabe of the National Astronomical Observatory.

Copyright 2002, Asahi Shimbun



>From Charles Cockell < >

Dear Benny,

The question of the polar dinosaurs and their survival of the K/T is an
interesting one. Of course we don't really know how they survived the polar
winter and what they ate, but I would contend that they probably depended
upon the brief polar summer and the resumption of photosynthesis for their
survival, as do large indigenous polar animals today. Most large polar
organisms depend upon the resupply of food during the summer when new plant
growth occurs during the light period (even if only for two months). They
either eat the plants directly or at least, if they are carnivores, they
depend upon the migration of prey to the polar regions during the summer
months that themselves eat photosynthetic organisms. Thus, survival of polar
darkness is not a ticket to survival of impact winters if impact winter
interferes with just one polar summer. There is the argument that if the
polar winter was in phase with the impact winter polar organisms could make
it through because perhaps they wouldn't notice what was happening anyway.
This might be true for the short-term, but their prey from lower latitudes
would be decimated and come summer they would be sure to be affected as a
direct result of the knock-on effect of disruption of migratory patterns at
the very least (and that's assuming the impact winter lasts only 6 months).

So I think it is possible to be comfortable with the idea of polar
ecosystems collapsing as much as low-latitude ecosystems as a result of
impact winter.


Dr. Charles Cockell,
British Antarctic Survey,
High Cross,
Madingley Road,

Tel : + 44 1223 221560
e-mail :


>From Duncan Steel < >

Hi Benny.

Professor David Williams has brought this to my attention:

It is likely to be of interested to all NEO watchers.




>From Jon Richfield < >

Hi Benny,

Scaling of our responses in reaction to the scale of a NEO threat.

Personal pressures have stopped me from keeping up to date on the threats
from NEOs lately, so forgive me if this note deals with material that has
been thoroughly re-masticated by other readers and participants already.

I appreciate that the greatest frequency of risk is from the small NEOs,
though I am intrigued to know what the cumulative risk is from NEOs as a
function of size and energy. For instance, do we face real life odds of
suffering more loss and damage from a billion ten metre objects, or from
a single ten kilometre object? In other words, are our deadliest and most
material enemies the city busters or the K/T killers? And in either case,
over what time scale?

The question gets worse when we consider some of the implications for
prevention. Suppose we have a couple of years of warning; in spite of a lot
of heart searching about what to do with a threatening city buster, I have
no doubt that we could nudge one far enough to turn a nearly-missed
collision into a nearly-hit by any of several methods.

How to deflect an object in the km range is a trickier matter, not to say
challenging. Also, the penalties for splitting the target into a shower of
smaller projectiles are questionable. I suspect that on average, a shotgun
blast of perhaps a few hundred megaton objects or a few million one ton
objects would do the occupants of our planet less harm than a single gigaton
object, but I am not volunteering to resolve the political consequences.
But, assuming that we could in fact be confident of preserving its
integrity, could we adequately deflect a gigaton object, given a year or so to prepare?

One reflects that the concept of averages is particularly treacherous here.
We could reduce a gigaton object to a swarm of particles with an average
mass of under a gram, using a very modest grenade: a few billion dust
particles, plus one gigaton mass.

But all that is just prefatory. If the NEO is a surprise visitor the size of
a planet, we might as well abandon ship; no foreseeable technology could
help us deflect a visitor the size of say Eros, in a few decades. Maybe,
just maybe, given a century or two, we could steer it the necessary few
thousand km by bombarding it with a few hundred Kuiper belt objects. I have
for a long time felt that we should be exploring the Kuiper belt for all we
are worth, including for the terraforming of Venus (our most tempting
terraforming prospect), but now it strikes me that I had underestimated the
value of the Kuiper belt. But in any case, we would not be able to do much
along those lines in a few decades.

Anyway, in our discussions of how to deflect NEOs, have we given enough
attention to the question of how well various methods would scale up to meet
larger and larger challenges? Which of the viable methods could be deployed
successfully within a decade, or within the lifetime of a human? Which
would work within the lifetime of a political system, such as democracy?
Which would work on rubble piles that are large enough to bind themselves
gravitationally in defiance of a megaton nuclear explosion? Would any work
on an object too large to maintain a non-spherical shape?

Have we yet had a conference, on line or in person, discussing the
technologies that, together or separately, would show promise? Are we in a
position to discuss which of those we could deploy within given time
periods, from a standing start? And how about discussing the value of those
technologies for more constructive purposes than simple fending off of NEO

Just thoughts in passing, or possibly passing thoughts.



PS. How many of us have read "The Star" by HG Wells, the all-time master of


>From Michael Paine

Dear Benny

The article by Luann Becker in Scientific American was excellent and gives
hope that "impact tracers" will be found for other major impacts. Note
however that she did not included the recently confirmed Woodleigh impact
structure in her list of impacts matching mass extinction events (~120km and

The magazine contains another item of relevance to CCNet: Down with
Evolution! Creationists are changing state educational standards
( )

This article reports that 40% of americans support the creationist view that
God created human life (and presumably the Earth) in the past 10,000 years.
So talking about events with an average interval of 1 million years might
not sink in! The worry is that politicians "represent" the people so perhaps
40% of politicians (probably more) have no interest in events on million
year timescales. But then I suppose 4 years is a very long time for a

Michael Paine


>From David James Johnson < >

Dear Benny,

The issues around the idea of a functional Planetary Defense System to some
sounds like Star Trek, and a fantasy. If you ask a congressman or Senator
about the issue, they may respond by asking which episode you are speaking
of, as they truly have no idea or concept in the reality of such a need. To
most it is simply away for the weapons scientist to develop new classes of
weapon systems. Thus it normally meets a swift death, or is hidden under the
cloak of National Security.

The idea of placing Missile Systems at Lagrangian points poses a host of
problems, in the form of Micro Meteor impacts, to fluxes in the solar wind
setting us up for possibly an even larger problem. Regardless of how much
the system is shielded, the potential of serious problems in a remote
weapons system are more than likely more problem than its worth. The list of
problems with such a systems deployment in space are extreme as they are
long. However, the placement of remote telescope and sensory equipment at
those points, may be a prudent move. Thus by providing us with another
vantage point, with abilities not capable by ground observation. Possibly a
LINEAR space station ?

Dr. Morrison is right about the Spaceguard Program being simply about Early
Warning, and the idea is a sound one. He and I may not agree on the size of
object we should be looking for, but I do understand their reasoning behind
the present NASA effort. However the Smaller and more frequent objects pose
more of a hazard than the ones we can presently see. Yet until we achieve a
space borne detection system, that can detect these smaller objects more
easily than the ground based systems, then we may not see much movement in
Government sponsored programs in this area.

Perhaps, the development of such systems will have to be done through the
graces of Private Donations, and some of the Non-Governmental Space Agency's
which seem to be popping up. Remember the SETI program went private after
the loss of Government funding, and it is thriving now, as well as utilizing
some Government systems.

There are no easy answers to these questions. However, new technology
sparked by new ideas may solve some of the dilemmas we face. The first
hurdle has been and still is, convincing Governments that there is a need of
the Spaceguard Program and an International effort. We often forget that
this is not simply a U.S. or UK problem, but one of a world problem. The UN
has become involved to some degree, and I would welcome their input.

The crux of the problem unfortunately will not be resolved before another
Tunguska type object slams into us again, this time we may not be as lucky
as in 1908. Yet in recent years, we see the Tunguska's smaller cousins hit
the upper atmosphere once or twice a year, and the only way we know is that
a Spy satellite happened to catch it, as the Nuclear Alarm bells were

When the Impact comes (as it is not a question of IF but WHEN), we will
probably be surprised and have little warning. Thus our response will more
than likely be an attempt to get the hell out of the way, if there is time.

For the past few years we have traded comments, and pursued various
arguments, yet we all mostly agree, that the threat exists, and we are going
to be hit. Yet in the years we've chatted about all of this, our Governments
are still slow to react or unresponsive. The primary reason is that they see
the time frames for the next impact a 100,000 years or so. So why should
they be concerned? For the 1Km and larger NEO's this may be true, but not
the smaller objects. So which is the greater Threat to life, the Planet
Killer with long duration orbit, or the smaller objects which are thus far
fairly unpredictable?

Should this be the subject of a Truly International Effort, I have always
thought so, However getting President Bush to really look at this subject,
and convince other Nations, that NEOs may be more of a danger than that of
Osama Bin Laden and other Terrorist groups is a questionable approach. We
will most likely always face such threats, and we will never be able to
totally wipe out these threats, thus the need for a unified network of
detection and defense is a must, and a necessity which all Nations will have
to realize.

In recent weeks we have seen the scientific community approach the
Australian Government with regards to the NEO program, as we need their eyes
in the Southern Hemisphere, and we have seen similar approaches with other
Governments such as Canada, and others are soon to follow, where we
scientist directly discuss the need for the NEO program. Perhaps this may
pave the way for a Truly International Cooperation.

Dr. David James Johnson

Stellar Research Group:

(US) Spaceguard Research & Survey:


>From The Times Record, 27 February 2002

By Johnathon Williams

FAYETTEVILLE - The chances of an major asteroid hitting the Earth are so
remote that it would not be wise to build a deflection system unless a
specific threat to the Earth was identified, a scientist with the Jet
Propulsion Laboratory said Monday.

Alan Harris, a senior research scientist with the lab, said the cost of
building a system capable of deflecting an incoming asteroid would be too
high to justify unless it was in response to a confirmed threat.

Because such a deflection system would probably use nuclear weapons, he
said, it could pose a serious threat to safety in and of itself. It's a
problem astronomer Carl Sagan called the "deflection dilemma," Harris said.

Scientists are now working under a congressional mandate to identify those
near-Earth asteroids whose orbits cross the Earth's path across the solar
system and could conceivably threaten the planet, Harris said.

"My real worry is that too many people will get frantic about the impact
hazard. ... I actually think we're doing about as much as we should," he

Harris made the remarks in a speech in the Poultry Science Auditorium at the
University of Arkansas. He was invited to speak by the UA-based
Arkansas-Oklahoma Center for Space and Planetary Sciences. The
jet-propulsion lab is in Pasadena, Calif.; it works closely with the
National Aeronautics and Space Administration on managing space missions and
conducting related research.

A system of telescopes is now scanning the sky in search of asteroids that
might one day strike the Earth, Harris said. The U.S. Congress in 1998 set a
goal of discovering within 10 years more than 90 percent of the asteroids
that could endanger the Earth.

That effort is now locating about nine such asteroids per month, he said.
Scientists think there are about 1,000 such asteroids in the sky; if that is
correct, the current rate of discovery will allow scientists to complete
their work on schedule, he said.

Throughout the Earth's history, Harris said, asteroid impacts have served as
an agent of great change in the evolution of species. The impact of an
asteroid ages ago is believed to have killed the dinosaurs, he said.

Small bodies frequently strike the Earth, Harris said, but most are
destroyed in the atmosphere. Of those that do make it through, most explode
before striking the ground. About 150 (sic) places around the globe have
been confirmed or are suspected to be impact sites, he said.

The real threat of a large asteroid is not in the immediate damage from the
impact, Harris said, but in the amount of dust it throws into the
atmosphere. An asteroid one kilometer across or larger could throw enough
dust into the atmosphere to block sunlight for several months, plunging the
planet into cold and darkness and destroying the worldwide agricultural
system, he said.

Despite the grim and severe possibilities, Harris said, the likelihood of
such an event occurring is extremely remote. Smaller asteroids that survive
the atmosphere have to strike a populated area on land to cause casualties,
a slim chance on a planet that is mostly water. The larger asteroids - the
extinction-level asteroids - can do tremendous damage regardless of where
they strike, he said, but such collisions occur only once about every 100
million years, he said.

The odds of a person in the United States being killed by the impact of an
extinction-level asteroid are about one in a million, he said.

That's compared to the odds of being killed in an earthquake, 1 in 150,000;
the odds of being killed in a plane crash, 1 in 20,000; or the odds of being
killed in a car crash, 1 in 100.

A person in the United States is much more likely to be asked to speak in
Fayetteville, Ark., Harris said, a chance of about 1 in 200,000.

Copyright 2002, The Times Record

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