PLEASE NOTE:
*
CCNet 96/2000 - 27 September 2000
---------------------------------
"More than half a century later,
scientists are beginning to
piece together the puzzle of an April 1,
1946 tsunami that
killed 159 people in Hawaii, smashed
into the Marquesas Islands
and kept going to Antarctica. 'The '46
tsunami is a huge, huge enigma,'
said Gerard Fryer, associate professor
in the University of Hawaii
Institute of Geophysics and Planetology.
It's a big worry because it
hasn't been explained, he said. 'The
waves were way, way too big for
the size of the earthquake (that
generated it). We're trying to figure
out everything we can about that.'"
-- Helen Altonn,
23 September 2000
"I am working to determine the
precise age for Rio Cuarto but this needs
to be done correctly rather than simply
saying it is so. Until this is done,
I think that connecting it to a specific
cause and effect is premature, as yet.
I hope I can make such a connection but
facts are needed first."
-- Peter
Schultz, 27 September 2000
"My question would be, is the
impact danger really that much greater than
is suggested by the statistics, or is it
a problem that it is fashionable to
blame impacts for all local disasters?
If it is the former, we have a problem
because the next Class 8 impact is
overdue. If it is the latter, care must be
taken to avoid enhancing the
"giggle factor" so often commented here. To do
this one must reject rapidly the more
unlikely cases leaving just the ones
where an impact is the most likely
explanation and concentrate on investigating
these with care.
-- Mark Kidger,
27 September 2000
(1) AN ASTEROID STRIKE IN THE PACIFIC OCEAN IN 1946?
Ron Baalke <baalke@zagami.jpl.nasa.gov>
(2) HOLY SMOKE: SQUARE CRATERS DETECTED ON EROS
NASA Science News <snglist@lyris.msfc.nasa.gov>
(3) REAL-WORLD DATA SHOW NO ARTIC WARMING OVER LAST 70 YEARS
CO2 Science, 27 September 2000
(4) NO SIGNIFICANT WARMING OR COOLING IN LAPLAND DURING THE LAST
100 YEARS
CO2 Science, 27 September 2000
(5) RISK ASSESSMENT OF CLIMATE CHANGE COMPARED TO OTHER
ENVIRONMENTAL
PROBLEMS
CO2 Science, 27 September 2000
(6) ASTRONOMERS FIND HEAT SOURCE FOR SUN'S CORONA
SpaceDaily, 27 September 2000
(7) PRECISE AGE OF RIO CUARTO IMPACT EVENT STILL UNKNOWN
Peter Schultz <Peter_Schultz@Brown.edu>
(8) IS IMPACT DANGER REALLY THAT MUCH GREATER THAN SUGGESTED BY
STATISTICS?
Mark Kidger <mrk@ll.iac.es>
(9) MODERATOR'S NOTE: BASIC PROBLEMS OF DETECTING HISTORICAL
IMPACTS
Benny J Peiser <b.j.peiser@livjm.ac.uk>
====================
(1) AN ASTEROID STRIKE IN THE PACIFIC OCEAN IN 1946?
From Ron Baalke <baalke@zagami.jpl.nasa.gov>
An asteroid strike in the Pacific ocean in 1946?
Ron Baalke
---------------------------------------------------------
PREPARING FOR THE NEXT BIG TSUNAMI
http://starbulletin.com/2000/09/23/news/story9.html
Scientists travel across the Pacific to study the 1946 tsunami
that killed
159 in Hawaii; their work may help create a warning system that
will save
lives the next time.
By Helen Altonn
Star-Bulletin (Honolulu, Hawaii)
September 23, 2000
MORE than half a century later, scientists are beginning to piece
together
the puzzle of an April 1, 1946 tsunami that killed 159 people in
Hawaii,
smashed into the Marquesas Islands and kept going to Antarctica.
"The '46 tsunami is a huge, huge enigma," said Gerard
Fryer, associate
professor in the University of Hawaii Institute of Geophysics and
Planetology.
It's a big worry because it hasn't been explained, he said.
"The waves were
way, way too big for the size of the earthquake (that generated
it). We're
trying to figure out everything we can about that."
Waves more than 100 feet high destroyed a lighthouse and killed
five people
on Unimak Island, Alaska, after a magnitude 7 earthquake in the
Aleutian
Islands.
Besides the Hawaii and Alaska victims, there was one death in
California and
two in French Polynesia -- a total of 167.
Fryer said the earthquake alone doesn't explain the large waves,
but it
shook loose a huge submarine landslide into the Aleutian Trench.
The combination possibly caused a narrow beam of very large
waves, he said.
"They just missed Hawaii but clobbered the Marquesas."
It's unlikely another tsunami as powerful could surprise Pacific
nations and
islands because it resulted in an international warning system,
said Fryer,
a state civil defense tsunami advisor.
However, the size of the waves could be seriously underestimated,
he said.
"We have to work out exactly what happened in 1946 so that
the next time
something happens, emergency managers around the Pacific can give
the
appropriate warnings."
THE last damaging tsunami across the Pacific was in 1964, Fryer
said.
"The one thing we know for certain is that there will be a
next time," said
Emile Okal, Northwestern University professor of geological
sciences.
Okal and Costas Synolakis, University of Southern California
professor of
civil and environmental engineering, joined Fryer in a recent
survey of the
1946 tsunami's effects in the Marquesas.
Also participating were Daniel Rousseau of USC and Gerard Guille
and
Philippe Heinrich of the French Atomic Energy Commission. The
commission and
National Science Foundation funded the work, resulting in "a
wealth of
information," Fryer said.
Hawaii and the Marquesas, the northernmost group in French
Polynesia, are
particularly vulnerable to tsunamis because they have almost no
offshore
reefs, he pointed out.
The large waves that raced across the Pacific in 1946 ran up the
western
coast of Antarctica to a height of 12 feet, he said. A British
Antarctic
Survey hut was destroyed.
The scientists were amazed at what they learned about the tsunami
in the
Marquesas.
Noting the people there only recently got television, Fryer said,
"Before,
they would tell stories to the kids, who passed on the
information. Kids
would tell us, 'Grandpa said there was a boat in this tree.'
"
The waves were larger there than the highest 56-foot waves in
Hawaii, he
said. They averaged 20 feet "and reached up phenomenally
high -- as much as
65 feet --in narrow valleys."
But the mid-day tsunami made a lot of noise; the first wave
wasn't the
largest, and people heeded warnings and escaped, the scientists
learned.
"There was a rapid flooding of the land but nobody was
overtaken by a wall
of water," Synolakis said.
The scientists went from one village to another by
four-wheel-drive truck,
boat and helicopter to interview eyewitnesses who were mostly
children in
1946.
They saw evidence of tsunami damage that occurred 54 years ago,
such as a
wrecked church or a coral boulder left by the waves.
They measured the maximum height reached on shore with standard
gear and
used the global positioning system to calculate the distance from
shore.
They hoped to get two or three measurements from each of three
islands, but
obtained more than 40 from 25 villages on five islands.
Fryer said the scientists went to the southern island of Fatu
Hiva last year
to investigate a little tsunami that happened after a cliff
collapsed.
They asked about other tsunamis and were so intrigued by what the
people
remembered about 1946 that they decided to go back this year, he
said.
ACCORDING to the people's accounts, the ocean retreated in the
early
afternoon of April 1, 1946, exposing rocks usually covered even
at low tide.
The ocean returned, hissing, and flooded the shore.
It subsided as much as 100 yards in some bays, then roared back
faster and
higher. The third wave was immense, then it slowly died.
The people had fled to high ground but the receding water
captured trees,
homes and livestock. Branches, coconuts, broken boats and houses,
and
thousands of stranded fish littered the coasts the next day.
A woman and her baby drowned in a village washed away by flooding
more than
half a mile inland on the island of Hiva Oa.
Fryer said the Marquesas findings have raised more questions.
For example, he said, there had to be big waves at Pitcairn and
Easter
Islands. But, how high?
There are also rumors that the San Juan Fernandez Islands between
Easter
Island and Chile had very large waves, he said.
"We realize we've got to get moving and get information
before all the
people who know it die."
Copyright 2000, Star-Bulletin
===============
(2) HOLY SMOKE: SQUARE CRATERS DETECTED ON EROS
From NASA Science News <snglist@lyris.msfc.nasa.gov>
NASA Science News for September 26, 2000
Square Craters
NASA's NEAR Shoemaker spacecraft has spotted square-shaped
craters on
asteroid Eros, a telltale sign of mysterious goings-on in the
asteroid belt long ago.
September 26, 2000 -- In the pantheon of cosmic geometry, curves
rule.
Astronomy texts are filled with spiral galaxies, elliptical
orbits, and ring nebulae.
There are no chapters on triangles or rectangles -- after all,
who ever heard of a
square planet? Some of the simplest shapes, common in the
handiwork of humans, are
just plain rare in space.
Rare, but not impossible...
Last month, astronomers were studying pictures of asteroid 433
Eros when
they noticed some unusual craters. Most impact craters are
circular, but these
were square!
An overzealous fan of Star Trek might mistake the impact scars
for places
where cube-shaped Borg vessels touched down and lifted off again,
but scientists
say they are natural -- albeit unusual -- features.
"These square craters are not just novelties, they tell us
something very interesting,"
says Andy Cheng of the Johns Hopkins University Applied Physics
Laboratory.
Cheng is the project scientist for NASA's Near Earth Asteroid
Rendezvous spacecraft,
which is orbiting Eros. "It's an indication that Eros is
permeated with an extensive
system of fractures and faults. Typically on Earth when we find
this type of fractured
area, the fractures form intersecting systems. Craters in such a
terrain look square;
we call them jointed craters. The best example is the Barringer
Meteor Crater in
Arizona."
Square craters add to accumulating evidence that Eros is riddled
with cracks
and ridges that extend the entire 33 km length of the
peanut-shaped space rock. "We
first saw long grooves in global pictures of the asteroid when
NEAR was entering orbit
around Eros in February 2000," continued Cheng. "Now,
if we look carefully, most of the
closeup pictures seem to show signs of grooves and ridges."
"We have to ask ourselves how these cracks could have
formed. Presumably
they are the result of large impacts. The question is: did these
impacts take place after
Eros was its present size and shape or while Eros was part of a
larger parent body?"
It's a question that goes to the heart of the asteroid's origin.
Scientists believe that billions of years ago, when the solar
system was
young and planets were newly-forming, Eros circled the Sun in an
orbit between Mars
and Jupiter. It was a denizen of the asteroid belt. Since then,
collisions with other
asteroids and gravitational perturbations by Mars and Jupiter
have altered
Eros's orbit, so that now it comes close enough to Earth to study
with spacecraft like NEAR.
We know a great deal about Eros today, but what was it like at
the dawn of
the solar system, before it became a "Near-Earth"
asteroid? Was Eros once part of a
moon-sized planet between Mars and Jupiter, or has it always been
an isolated space
rock?
"If continued mapping confirms that faults and ridges extend
from one end of
Eros to the other, I would consider it to be strong evidence that
Eros is a piece of
something that was once much larger," says Cheng. If all of
the rocks in the modern-day
asteroid belt were assembled, they would form a small planet
about 1500 km in diameter --
roughly half the size of Earth's moon. Such a body might have
existed in an orbit between
Mars and Jupiter billions of years ago, before it shattered as a
result of collisions
with other planetoids.
But if Eros is a "chip off the old block," there's a
new mystery to
consider. When rocky planets like the Earth and its moon (and
maybe the parent body of Eros) are
formed, heavier elements sink to the core while lighter ones
remain near the
crust. This leads to a core-mantle structure with distinctive
chemical signatures in each layer.
The looming conundrum is that Eros does not exhibit the chemical
signatures
of differentiation. NEAR X-ray spectrometer data show that
aluminum, magnesium,
and silicon on Eros have the same relative abundances that they
do in the Sun and in the
early solar nebula. Evidently, Eros was not part of a body that
experienced the
Earth-like process of heating and segregation of metals from
silicates to form an iron core and
rocky mantle.
"Eros is an example of a very primitive body ... nothing
much has happened
to it other than formation and cratering. If you want the most
pristine material in the
solar system [where very little has happened] Eros is a good
example," says Joe Veverka,
professor of astronomy at Cornell University, and the principal
investigator
for two of NEAR's cameras.
Can Eros be both -- a primitive, undifferentiated body and a
fragment from a
long-ago planetoid? It's a possible contradiction that puzzles
researchers.
"Even before we visited Eros we knew that asteroids were a
mixed group --
some appear to be differentiated and some not," says Cheng.
"The largest asteroid of all,
933 km-wide Ceres, is not differentiated. Yet, we believe it's
possible for objects even
smaller than Ceres to melt and chemically segregate. We simply
don't know why some
asteroids appear to be more primitive than others. We have to
reserve a little
skepticism here and pursue this mystery."
Cheng says that a global map of Eros's grooves and ridges -- and
possibly
more square craters -- will likely shed new light on the
asteroid's history. For now
researchers and asteroid enthusiasts wait with anticipation as
NEAR Shoemaker continues
its first-ever and often surprising survey 433 Eros, knowing that
the best answers and most
perplexingmysteries may be yet to come.
For more information about asteroid Eros and the NEAR mission,
please visit
the Near-Earth Asteroid Rendezvous mission home page at
http://near.jhuapl.edu. The
Johns Hopkins
University Applied Physics Laboratory in Laurel, MD, designed and
built the
NEAR spacecraft and manages the mission for NASA.
================
(3) REAL-WORLD DATA SHOW NO ARTIC WARMING OVER LAST 70 YEARS
From CO2 Science, 27 September 2000
http://www.co2science.org/journal/2000/v3n24c1.htm
Przybylak, R. 2000. Temporal and spatial variation of
surface air
temperature over the period of instrumental observations in the
Arctic. International Journal
of Climatology 20: 587-614.
Background
According to nearly all climate models, earth's polar regions
should be the
most sensitive and vulnerable areas of the planet to climate
change; and, in the
words of the author of this treatise, "warming and cooling
epochs should be seen most
clearly here and should also occur earlier than in other parts of
the world."
Hence, as he continues, earth's polar regions "should play a
very important role in the
detection of global changes," and we assume that it was that
rational that led him to
conduct this comprehensive study of temporal and spatial
variations in Arctic
surface air temperature over the period of instrumental
observations.
What was done
Mean monthly temperatures of 37 Arctic and 7 sub-Arctic stations,
as well as
temperature anomalies of 30 grid-boxes from the updated data set
of Jones
were used to derive a number of different spatial and temporal
histories of
Arctic near-surface air temperature.
What was learned
In the words of the author:
1. "In the Arctic, the highest temperatures since the
beginning of
instrumental observation occurred clearly in the 1930s."
2. "Even in the 1950s the temperature was higher than in the
last 10 years."
3. "Since the mid-1970s, the annual temperature shows no
clear trend."
4. "The level of temperature in Greenland in the last 10-20
years is similar
to that observed in the 19th century."
What it means
Again in the words of the author, the meteorological record
"shows that the
observed variations in air temperature in the real Arctic are in
many aspects not
consistent with the projected climatic changes computed by
climatic models for the
enhanced greenhouse effect," because, of course, "the
temperature predictions
produced by numerical climate models significantly differ from
those actually observed."
Copyright © 2000. Center for the Study of Carbon Dioxide
and Global Change
=================
(4) NO SIGNIFICANT WARMING OR COOLING IN LAPLAND DURING THE LAST
100 YEARS
From CO2 Science
http://www.co2science.org/journal/2000/v3n24c2.htm
Lee, S.E., Press, M.C. and Lee, J.A. 2000. Observed
climate variations
during the last 100 years in Lapland, northern Finland.
International Journal of
Climatology 20: 329-346.
What was done
The authors analyzed Finnish Lapland meteorological data obtained
from local
meteorological stations and from the National Oceanic and
Atmospheric
Administration for a 5° latitude by 5° longitude grid in order
"to assess whether there is
any evidence of a change in climate in this region over the last
100 years."
What was learned
In the words of the authors, "there has been no significant
warming or
cooling during the entire period 1876-1993 for the annual data
and the seasonal
temperature data."
What it means
Once again, and from the part of the world - high northern
latitudes - where
CO2-induced warming is predicted to be particularly dramatic,
real-world data reveal no
net warming over the last 117 years.
Copyright © 2000. Center for the Study of Carbon Dioxide
and Global Change
================
(5) RISK ASSESSMENT OF CLIMATE CHANGE COMPARED TO OTHER
ENVIRONMENTAL
PROBLEMS
From CO2 Science
http://www.co2science.org/journal/2000/v3n24c5.htm
SOCIETAL IMPACT OF CLIMATE CHANGE: MOUNTAIN OR MOLEHILL
Goklany, I.M. 2000. Potential consequences of increasing
atmospheric CO2
concentration compared to other environmental problems.
Technology 7S: 189-213.
What was done
The author "examines the validity of the assertion that
anthropogenic
climate change is the overriding environmental concern facing the
globe today," looking at
recent trends in various climate-sensitive phenomena such as
global food security, U.S.
deaths due to storms and floods, global death rates due to
infections and parasitic
diseases, and the biomass of northern forests. Then, based
upon the Intergovernmental Panel
on Climate Change's 1995 Impact Assessment, the author evaluates
the projected global
impacts of climate change upon food security, deforestation,
biodiversity and human
health several decades into the future.
What was learned
The author's analyses reveal that over the next several decades
the
climate-sensitive phenomena investigated will likely be an order
of magnitude smaller in
significance than those due to other stressors of society, such
as population growth, poverty,
land conversion and non-climate-change-related rates of
infectious and parasitic diseases.
What it means
In the words of the author, "eliminating anthropogenic
climate change, even
if feasible, would - for the next several decades - do little to
reduce the much larger
baseline rates of global deforestation, biodiversity loss, and
infectious and parasitic
diseases." Consequently, the author concludes that
man-induced climate
change "is not today - nor [is it] likely to be in the
foreseeable future - as urgent as other
current environmental and public health problems."
This being the case, why is there so much angst over potential
global
warming? Do the people behind the movement to reduce
emissions of life-supporting CO2 not
really care about the truly pressing environmental concerns of
our day? Do they have
some alternative agenda they are pushing, for which concern about
potential global warming
serves as a convenient lever by which they can move the masses in
the direction they
desire? Or are they just plain ignorant? Mercy would
suggest the latter alternative; but
these people are not stupid. Hence, the former possibility
emerges as the more likely
stimulus for their actions. Then again, who really knows? And
does it even
matter?
Copyright © 2000. Center for the Study of Carbon Dioxide
and Global Change
==============
(6) ASTRONOMERS FIND HEAT SOURCE FOR SUN'S CORONA
From SpaceDaily, 27 September 2000
WASHINGTON (AFP) - September 27th, 2000 - Astronomers have
located the
mysterious source that makes the sun's corona 1,000 times
hotter than its visible
surface, NASA said Tuesday.
"The mysterious energy source that makes the Sun's
atmosphere so incredibly
hot has been an enigma for more than 70 years, and before we
discover what it is we
need to learn where it is," said Markus Aschwanden of the
Lockheed-Martin Solar and
Astrophysics Laboratory in Palo Alto, California.
New observations from the TRACE space observatory reveal the
location of the
unidentified energy source, showing that most of the heating
occurs low in
the corona, at a distance of no more than 16,000 kilometers
(10,000 miles) from the
Sun's visible surface, according to Aschwanden's study, published
in the Astrophysical
Journal.
Composed of gas, the corona is visible as a halo around the sun
during a
total eclipse.
"Locating the source of coronal heating is a key piece of
this puzzle, and
we are excited that solar observatories like TRACE are allowing
us to resolve the
hidden events occurring in the atmospheres of stars,"
Aschwanden said.
TRACE, which stands for Transition Regional and Coronal Explorer,
was
launched in 1998 to explore the upper solar atmosphere.
All rights reserved. © 2000 Agence France-Presse.
============================
* LETTERS TO THE MODERATOR *
============================
(7) PRECISE AGE OF RIO CUARTO IMPACT EVENT STILL UNKNOWN
From Peter Schultz <Peter_Schultz@Brown.edu>
Hi Benny,
I want to correct something in an article in your latest CCNET.
Rio
Cuarto was cited as a "confirmed" age and consequence
for climate change.
I would like to know where this age was obtained since nothing
has been
published or confirmed. If this is based on a climate signal
and then tied to an approximate date of Rio Cuarto, then this is
circular
reasoning: can't use an observed climate change to date the
impact and then
relate this impact to a climate change. I am working to determine
the precise age for Rio Cuarto but this needs to be done
correctly rather
than simply saying it is so. Until this is done, I think
that connecting
it to a specific cause and effect is premature, as yet. I hope I
can
make such a connection but facts are needed first.
Pete
================
(8) IS IMPACT DANGER REALLY THAT MUCH GREATER THAN SUGGESTED BY
STATISTICS?
From Mark Kidger <mrk@ll.iac.es>
Dear Benny:
I was interested by the contribution of Ed Grondine in today's
CCNet.
However, some of the numbers quoted look a little inconsistent
when referring to
possible historical impact sites.
If we take just the numbers for Class 9 and 10 events I think
many readers
will have noticed something very odd. A Class 10 event is given
to be once
every 100 000 years or less frequently. In other words, in all
human history
- say 8000 years - there is less than a 10% chance of registering
even a
single event. However we have one confirmed and a further five
possible
events in just 5000 years in this list.
For Class 9 events we have a similar picture. Here we have events
that would
be no more frequent than one per 1000 years and, on average, one
per 10 000.
In this case we have no less than five possible events in less
than 1500
years.
Even in the Class 8 events we have a suggested rate of one per 50
years
MAXIMUM, yet even not counting the atmosphere grazing asteroid in
1972 that
was observed crossing the USA in daylight and which is not
included, we have
5 events in less than 150 years.
My question would be, is the impact danger really that much
greater than is
suggested by the statistics, or is it a problem that it is
fashionable to
blame impacts for all local disasters? If it is the former, we
have a
problem because the next Class 8 impact is overdue. If it is the
latter, care must
be taken to avoid enhancing the "giggle factor" so
often commented here. To do
this one must reject rapidly the more unlikely cases leaving just
the ones
where an impact is the most likely explanation and concentrate on
investigating these with care.
Mark Kidger
=====================
(9) MODERATOR'S NOTE: BASIC PROBLEMS OF DETECTING HISTORICAL
IMPACTS
From Benny J Peiser <b.j.peiser@livjm.ac.uk>
Research on historical impacts is still in its infancy. In many
ways, the
current state of affairs is comparable to the equally awkward
situation in which the
early researchers on impact cratering processes found themselves
between the mid
19th and the mid 20th centuries.
It should be recalled that it took more than 100 years before the
initial
impact hypothesis for many lunar and terrestrial craters could be
finally verified by Gene
Shoemaker's comprehensive study of the Arizona meteor crater in
the 1960s. It was only
after Gene proved beyong any doubt that impact craters have as a
feature specific
impact-derived fingerprints, such as shocked quartz, and that
these are
entirely distinct from volcanic craters, that the (often
riddiculed) impact cratering
hypothesis became a scientific fact.
Those of us, who are hypothesising a similar causation for a
number of
historical catastrophes find themselves in a position where
neither unambiguous
fingerprints (other than a small number of impact craters of
dubious age) nor adequate
research metholds exist. That's why Ed Grondine's list of
confirmed and suspected
impacts is not only speculative but also flawed to a large
extent. I suspect
that up to 80% of his listed impacts may turn out to be
chimerical. Mark Kidger has
hit the nail on the head when he calls for the elimination of all
those
immaterial impacts as soon as possible. But in order to rule out
that some or even most
of the suggested disasters were due to cosmic impacts, we need to
do our
homework first and search geographical locations for
fingerprints. That's exactly
what Ed and others, in particular NEO researchers here in the UK,
have been promoting
for some time.
While Ed's list may be largely flawed, Michael Paine's computer
simulation
(based on the current asteroidal flux) suggests that a typical
10,000 year
period (assuming a constant population of 5 billion people) will
produced a
staggering number of impacts. Nobody, to my knowledge, has so far
questioned the
accuracy of these estimates - so here they are again:
* 110 fatal events resulting in a total of 13 million
fatalities (an average of 120,000 fatalities per event).
* 300 "Tunguska" style airbursts over land, with 80 of
these producing fatalities (roughly 1 fatal event per
century).
* 12 ocean impacts that produce tsunami, with an average of
500,000 fatalities per event.
* Just 4 land impacts (leaving craters), with an average of
500,000 fatalities per event.
For further details, see
(http://www1.tpgi.com.au/users/tps-seti/sta1047.htm)
But where, then, are the hundreds of smoking guns for all these
impacts and,
more importantly, how can we find them if we were to look for
them? You
don't have to be a rocket scientist to figure out that there is
an unmistakable
discrepancy between the minute number of known Holocene impact
structures (~14) on the
on hand and the number of impacts (~500) expected to occur during
an 'average'
10,000 year period.
While Ed's list most certainly includes many artificial impact
events, it
doesn't take account of the hundreds of unknown impacts which
still await discovery.
Until such search programmes are established as part of
conventional impact risk
assessment and NEO research, it might take us another 100 years
to develop a sound and
valid method to detect Tunguska-type, i.e. crater-less impact
disasters in the
geological, archaeological and environmental records. Thankfully,
the UK Task Force on
NEOs has recommended that "the Government should help
promote multi-disciplinary
studies of the consequences of impacts from Near Earth Objects on
the Earth
in British and European institutions concerned, including
Research Councils, universities and the
European Science Foundation." (Recommendation 8: Studies of
impacts and
environmental and social effects)).
If we could make as much progress in the field of historical
impact research
as we have in the field of NEO detection, we should be able to
assess the overall
impact hazard much more reliably than we currently can.
Benny J Peiser
----------------------------------------
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