SETI bioastro: Fw: CCNet: MULTIPLE IMPACTS MAY HAVE CAUSED K/T MASS EXTINCTION

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From: LARRY KLAES (ljk4@msn.com)
Date: Thu Nov 07 2002 - 09:07:41 PST

Previous message: LARRY KLAES: "SETI bioastro: Take a Chance to Write the Future"

NEW THEORY ON DINOSAURS: MULTIPLE IMPACT DID THEM IN

>From The New York Times, 5 November 2002

http://www.nytimes.com/2002/11/05/science/life/05CRAT.html?ex=1037250000&en=
c771927311f6e53f&ei=5040&partner=MOREOVER

By WILLIAM J. BROAD

For more than a decade, most scientists have believed that the extinction of
the dinosaurs was caused by a single event: the crash of an immense body
from outer space, its explosive force like a hundred million hydrogen bombs,
igniting firestorms and shrouding the earth in a dense cloud of dust that
blocked sunlight and sent worldwide temperatures plummeting.

The theory gained wide acceptance in 1991, after the discovery of a crater
buried under the tip of the Yucatán Peninsula. The giant gash stretched 110
miles from rim to rim, and its age was found to be 65 million years, the
same time as the death of the dinosaurs.

Now, however, scientists working in Ukraine have discovered that a
well-known but smaller crater, some 15 miles wide, had been inaccurately
dated and is actually 65 million years old, making the blast that created it
a likely contributor to the end of the dinosaurs.

So too, a British team has recently found a crater at the bottom of the
North Sea dating to the same era and stretching over 12 miles in a series of
concentric rings.

The discoveries are giving new support to the idea that killer objects from
outer space may have sometimes arrived in pairs or even swarms, perhaps
explaining why the extinctions seen in the fossil record can be messy
affairs, with species reeling before a final punch finishes them off.

"It's so clear," said Dr. Gerta Keller, a geologist and paleontologist at
Princeton, who studies the links between cosmic bombardments and life
upheavals. "A tremendous amount of new data has been accumulated over the
past few years that points in the direction of multiple impacts."

But Dr. Keller added that many scholars had staked their reputations on the
idea of a single dinosaur-ending disaster and were reluctant to consider the
new evidence. "Old ideas," she said, "die hard."

Her own research, Dr. Keller added, suggests the reality of multiple strikes
and raises doubts that the Yucatán rock, whose crater is known as Chicxulub,
was the event that sealed the dinosaurs' fate. Instead, she said, the main
killer "has yet to be found."

The ferment is prompting scientists around the globe to look for new craters
and to reassess the ages of old ones in search of clues to the wave of
global extinction that did in thousands of species - not only the dinosaurs
but many plants, fish and plankton - at the end of the Cretaceous period.

"There are over 170 confirmed craters on earth and we know the precise
impact age of only around half," said Dr. Simon P. Kelley of the Open
University in Britain, who found the dating error on the Ukraine crater,
along with Dr. Eugene P. Gurov of the Institute of Geological Sciences in
Ukraine. Even in the United States, he added, several craters are poorly
dated.

"In the U.K., we have a phrase, `You wait an hour for a bus, then three come
along all at once,' " he remarked in an interview. "Maybe impacts are like
that."

The idea that a giant intruder from outer space killed off the dinosaurs was
proposed in 1980 by Dr. Luis W. Alvarez; his son, Dr. Walter Alvarez; and
their colleagues at the University of California at Berkeley. It was met
with great skepticism at first, but in time became the standard belief.

In his 1997 book, "T. Rex and the Crater of Doom," Dr. Walter Alvarez, a
geologist, said he had considered the possibility of multiple impacts until
1991 and the discovery of the huge Yucatán crater, which seemed big enough
to solve the mystery on its own.

Dr. Kelley and Dr. Gurov presented their findings from Ukraine in the August
issue of the journal Meteoritics & Planetary Science. In geologic time, the
twin birth throes of the Ukraine and Yucatán craters, they note, suggest
rather than prove "that they combined to lead to the mass extinction" at the
end of the Cretaceous period and raise questions of other possible cosmic
killers.

Known as Boltysh, the newly dated crater lies in eastern Ukraine in the
basin of the Tyasmin River, a tributary of the Dnieper. Though just 15 miles
wide, the buried crater, whose presence is revealed by deep jumbled masses
of melted and broken rocks, is surrounded by a ring of rocky debris that
extends over many hundreds of square miles, conjuring up a fiery cataclysm.
The two scientists say in their report that this kind of crash today would
have devastated a densely populated nation.

Over the years, scientists had analyzed rocky samples from the Boltysh
crater and found ages ranging from 88 million to 105 million years.

The new dating of the crater by Dr. Kelley and Dr. Gurov used a highly
accurate method that carefully measures the ratio of two isotopes of the
element argon, a colorless, odorless gas that makes up about 1 percent of
the earth's atmosphere. Argon-argon dating works because the isotopes decay
at different rates. By measuring the ratio, it is possible to estimate how
long ago the sample melted to trap atmospheric argon.

Dr. Kelley and Dr. Gurov report that seven samples of melted rock from the
depths of the Boltysh crater yielded an average age of 65.2 million years,
with an accuracy of plus or minus 600,000 years.

By contrast, Chicxulub (pronounced CHEEK-soo-loob) has been dated to 65.5
million years, plus or minus 600,000. Given the range of dating uncertainty,
the two impacts that made the craters may have occurred simultaneously or
been separated by thousands of years.

Scientists have recently looked more favorably at the idea that comets can
travel in packs. In the 1980's, a few speculated that comet showers might
produce strikes on the earth over a period of a million years or so to bring
on extinctions. The idea gained support in 1994 when the comet
Shoemaker-Levy 9 was fractured by the gravitational pull of Jupiter into 21
discernible pieces that then, one by one, bombarded the planet.

Dr. Kelley and colleagues at the University of Chicago and the University of
New Brunswick, writing in the journal Nature in 1998, gave precise dating
evidence to argue that a similar kind of celestial barrage hit the earth 214
million years ago. Spread over Europe and North America, the chain of five
craters, they wrote, indicated that a large comet or asteroid had broken up
and struck the earth in a synchronized assault.

Today, Dr. Kelley said, the odds of the Boltysh and Chicxulub craters'
having formed simultaneously, like the chain, are not great. Still, even if
their times of impact prove to have been only close, experts say, the
one-two punch could still have added to the global turmoil that did in the
dinosaurs and other creatures.

Beneath the North Sea, two British oil geologists have found another crater,
buried under hundreds of feet of ooze, that may have contributed to the
chaos. Writing in the Aug. 1 issue of Nature, Simon A. Stewart and Philip J.
Allen said they were able to date the 12-mile structure to a period 60
million to 65 million years ago. They named it Silverpit, after a nearby
sea-floor channel.

Experts say the new finds may answer an old criticism of the single-impact
theory. Critics, especially the paleontologists who specialize in dinosaur
extinction rates, had long noted that the fossil record of the late
Cretaceous shows a slow decline of many life forms rather than a single vast
die-off. That seemed inconsistent with a cosmic catastrophe.

But now, the emerging family ties among the Boltysh, Silverpit and Chicxulub
craters suggest that a series of impacts may have driven or contributed to
this slow decline.

Dr. Keller of Princeton and her colleagues have found signs of other
intruders from outer space that hit at slightly different times about 65
million years ago, strengthening the gradualist idea.

Working in northeastern Mexico, they discovered that glass spheres of melted
rock once thought to have been thrown out by the Chicxulub impactor were
more likely the result of at least two separate disasters, about 300,000
years apart. They recently presented their findings in a paper for the
Geological Society of America.

Moreover, Dr. Keller said, the evidence suggests that the earlier of the two
cataclysms formed the Chicxulub crater, making its arrival too early to
account for the killer punch of the dinosaur extinction.

Geologic clues that she and her colleagues are collecting from Mexico,
Guatemala, Haiti and Belize, Dr. Keller said, suggest that a barrage of
cosmic bodies hit the earth over the course of 400,000 years. The first was
the Chicxulub event, the second the unlocated impactor at the end of the
Cretaceous period and then a straggler some 100,000 years later.

Strong evidence exists for three impacts at the end of the Cretaceous era,
Dr. Keller said, followed by wide climate shifts that lasted through the
turbulent period.

While geologists hunt for other craters and impact events, they say the most
compelling evidence of all may have vanished. Since the earth's surface is
more than 70 percent water, it is likely that most signs of speeding rocks
from space disappeared long ago in the churning geological processes that
constantly renew the seabed. The North Sea, being relatively shallow, is an
exception.

Despite the inherent difficulties of the research, Dr. Kelley of the Open
University said he planned to redouble his hunt to "try to solve this
problem."

MODERATOR'S NOTE: For more background information on the multiple K/T
impacts theory see CCNet issues 107/2002 and 109/2002:

CCNet 107/2002 - 17 September 2002
#1: MULTIPLE COMETARY IMPACTS & THE K/T MASS EXTINCTION?
http://abob.libs.uga.edu/bobk/ccc/cc091702.html

CCNet 109/2002 - 19 September 2002
#8: GERTA KELLER: MULTIPLE COMETARY IMPACTS AT K/T TIME
http://abob.libs.uga.edu/bobk/ccc/cc091902.html

(10) TAKE A CHANCE TO WRITE THE FUTURE

>From Andrew Yee <ayee@nova.astro.utoronto.ca>

ESA News
http://www.esa.int

4 November 2002

Take a chance to write the future

The only way of discovering the limits of the possible is
to venture a little way past them into the impossible.
- Arthur C. Clarke

>From Cyrano de Bergerac's 17th century trip to the Moon and Jules Verne's
19th century Nautilus submarine right up to William Gibson's navigations
through cyberspace and Kim Stanley Robinson's colonisation of Mars, authors
have always signposted the shape of things to come.

Now ESA is giving young science fiction writers the chance to showcase their
own future visions with a worldwide competition.

The Clarke-Bradbury International Science Fiction Competition is named in
honour of Arthur C. Clarke and Ray Bradbury, whose writings have inspired
generations of space scientists and explorers.

To highlight this vital connection between initial idea and later reality,
writers aged between 15 and 30 are invited to submit short (2500 word
maximum) stories dealing with the technologies of space travel, exploration
or settlement.

"I hope the competition will attract many entries, and inspire more and more
young people to take to writing science fiction," said Arthur C. Clarke.
"Today's youth take for granted the marvels of modern technology, many of
which were envisioned in the science fiction of my youth (and some of my own
stories!)"

"Last year ESA carried out a detailed survey of science fiction concepts in
search of those worth real-world development which culminated in a
beautifully illustrated brochure. Continual technological progress means
ideas that were once wild speculation may now have come within
the bounds of feasibility", noted ESA's David Raitt, organizer of the
competition.

Take the exotic concept of the 'space elevator'. In 1895 Russian theorist
Konstantin Tsiolkovsky was inspired by a trip to the Eiffel Tower to imagine
a tower reaching up to orbital altitude. Arthur C. Clarke brought the idea
up to date in his 1979 novel The Fountains Of Paradise.
Crews and cargo could ride elevators up the tower into space.

Now science has discovered a material called carbon nanotubes, strong enough
to withstand the tensile stresses an orbital tower would experience. Current
thinking suggests that a space elevator could be built within the next dozen
years or so. Seattle-based HighLift Systems is well advanced with
theoretical and initial development work and estimates that the space
elevator would reduce launch costs to a mere Euro 10/kg!

Solar or light sails are another SF concept -- first featured in the short
stories of Cordwainer Smith and the Arthur C. Clarke tale 'Sunjammer' and
set to become reality much sooner. Once unfurled, sails can either be
propelled by light from the Sun or alternatively a continuously-firing
laser.

Proving the basic concept, a bowl-shaped 'lightship' has been lifted 20
metres high by laser pulses in the USA. While in Europe, ESA and DLR have
designed a prototype 20 metre square solar sail for future space flight.

During the ESA study for closer examination more than 250 such technology
concepts were collected by scientists, engineers, science fiction writers
and laymen from science fiction literature and films. And the hope is that
the competition could uncover or generate yet more promising ideas.

Five stories will be selected by an international jury to receive prizes and
from these a Winner will be chosen who will be invited to present his/her
story at the 2003 International Astronautical Congress in Bremen, Germany.
All the best entries will be published in a book by ESA.

The deadline for entries is 28th February 2003. Anyone interested in giving
the competition a try can find out more here or contact:

David Raitt
Technology Transfer and Promotion Office
European Space Agency, ESTEC, The Netherlands
email: david.raitt@esa.int

More information

* ITSF competition
http://www.itsf.org/index.php?PAGE=contest%2Findex.html

* BR-176 brochure: Innovative Technologies from Science
Fiction for Space Applications (pdf)
http://esapub.esrin.esa.it/br/br176/BR176.pdf