PLEASE NOTE:


*

CCNet 77/2003 - 26 September 2003
"CHICXULUB IMPACT CRATER NOT RELATED TO K/T MASS EXTINCTION"
--------------------------------------------------------


[Gerta] Keller has accumulated evidence suggesting that the Chicxulub
crater probably did not coincide with the K/T boundary. Instead, the
impact that caused the Chicxulub crater was likely smaller than
originally believed and probably occurred 300,000 years before the mass
extinction. The final dinosaur-killer probably struck Earth somewhere else
and remains undiscovered, said Keller.... If the majority of scientists
eventually reduce their estimates of the damage done by a single asteroid,
that shift in thinking could influence the current-day debate on how much
attention should be given to tracking and diverting Earth-bound asteroids
and comets in the future.
     --Steven Schultz, Princeton University, 25 Sept. 2003


This affair has become an object lesson on how partisan and unethical the
whole dinosaur controversy has become. Young scientists are now refusing to
get involved in this field because no matter what they say it will offend
someone and dam age their careers. It's like the nature-nurture debate.
No matter what you say, someone will hate you for it.
    --Norman MacLeod, Natural History Museum, 7 Sept. 2003


To me it is inconceivable that there should be any branch of science where
first impressions about the meaning of one's data are published. That is why
the entire concept of the Torino scale makes no sense to me. That is like
asking me to publish any passing thought I may have about my experiments.
Something has got to change.
      --Gerrit Verschuur, CCNet, 26 Sept. 2003


(1) "CHICXULUB IMPACT CRATER NOT RELATED TO K/T MASS EXTINCTION"

(2) WHAT KILLED THE DINOSAURS? GERTA KELLY REKINDLES K/T CONTROVERSY

(3) I'VE GOT A BONE TO PICK WITH YOU, SAY FEUDING DINOSAUR EXPERTS

(4) NEW EARLY PROTEROZOIC MEGA-IMPACT FALLOUT UNIT, PILBARA CRATON

(5) SPACE ROCK'S CLOSE CALL

(6) THE DISCOVERY OF 2003 SW130

(7) THOUGHTS ON IMPACT RISK ASSESSMENT

(8) FORECAST OF A BIG EARTHQUAKE AND NEO COLLISION ALERTS

(9) K/T CONTROVERSY: WE SHOULD BE OPEN TO NEW SCIENTIFIC EVIDENCE

(10) "NEW THEORY ON DINOSAUR EXTINCTION": SLOPPY PRESS RELEASE

(12) AIAA PLANETARY DEFENSE CONFERENCE (PDC) PROGRAM AND NASA SMALL NEO HUNT

(13) AND FINALLY: FORGET ASTEROIDS, GAMMA RAYS MAY HAVE DEVASTATED LIFE ON EARTH

===============
(1) "CHICXULUB IMPACT CRATER NOT RELATED TO K/T MASS EXTINCTION"

Ron Baalke <info@jpl.nasa.gov>

http://www.princeton.edu/pr/news/03/q3/0925-keller.htm

Princeton University
Office of Communications
22 Chambers St.
Princeton, New Jersey 08542
Telephone 609-258-3601; Fax 609-258-1301

For immediate release: September 25, 2003
Contact: Steven Schultz, (609) 258-5729, sschultz@princeton.edu

Princeton paleontologist produces evidence for new theory on
dinosaur extinction

PRINCETON, N.J. -- As a paleontologist, Gerta Keller has studied
many aspects of the history of life on Earth. But the question
capturing her attention lately is one so basic it has passed the
lips of generations of 6-year-olds: What killed the dinosaurs?

The answers she has been uncovering for the last decade have
stirred an adult-sized debate that puts Keller at odds with many
scientists who study the question. Keller, a professor in
Princeton's Department of Geosciences, is among a minority of
scientists who believe that the story of the dinosaurs' demise is
much more complicated than the familiar and dominant theory that a
single asteroid hit Earth 65 million years ago and caused the mass
extinction known as the Cretacious-Tertiary, or K/T, boundary.

Keller and a growing number of colleagues around the world are
turning up evidence that, rather than a single event, an intensive
period of volcanic eruptions as well as a series of asteroid
impacts are likely to have stressed the world ecosystem to the
breaking point. Although an asteroid or comet probably struck Earth
at the time of the dinosaur extinction, it most likely was, as
Keller says, "the straw that broke the camel's back" and not the
sole cause.

Perhaps more controversially, Keller and colleagues contend that
the "straw" -- that final impact -- is probably not what most
scientists believe it is. For more than a decade, the prevailing
theory has centered on a massive impact crater in Mexico. In 1990,
scientists proposed that the Chicxulub crater, as it became known,
was the remnant of the fateful dinosaur-killing event and that
theory has since become dogma.

Keller has accumulated evidence, including results released this
year, suggesting that the Chicxulub crater probably did not
coincide with the K/T boundary. Instead, the impact that caused the
Chicxulub crater was likely smaller than originally believed and
probably occurred 300,000 years before the mass extinction. The
final dinosaur-killer probably struck Earth somewhere else and
remains undiscovered, said Keller.

These views have not made Keller a popular figure at meteorite
impact meetings. "For a long time she's been in a very
uncomfortable minority," said Vincent Courtillot, a geological
physicist at Université Paris 7. The view that there was anything
more than a single impact at work in the mass extinction of 65
million years ago "has been battered meeting after meeting by a
majority of very renowned scientists," said Courtillot.

The implications of Keller's ideas extend beyond the downfall of
ankylosaurus and company. Reviving an emphasis on volcanism, which
was the leading hypothesis before the asteroid theory, could
influence the way scientists think about the Earth's many episodes
of greenhouse warming, which mostly have been caused by periods of
volcanic eruptions. In addition, if the majority of scientists
eventually reduce their estimates of the damage done by a single
asteroid, that shift in thinking could influence the current-day
debate on how much attention should be given to tracking and
diverting Earth-bound asteroids and comets in the future.

Keller does not work with big fossils such as dinosaur bones
commonly associated with paleontology. Instead, her expertise is in
one-celled organisms, called foraminifera, which pervade the oceans
and evolved rapidly through geologic periods. Some species exist
for only a couple hundred thousand years before others replace
them, so the fossil remains of short-lived species constitute a
timeline by which surrounding geologic features can be dated.

In a series of field trips to Mexico and other parts of the world,
Keller has accumulated several lines of evidence to support her
view of the K/T extinction. She has found, for example, populations
of pre-K/T foraminifera that lived on top of the impact fallout
from Chicxulub. (The fallout is visible as a layer of glassy beads
of molten rock that rained down after the impact.) These fossils
indicate that this impact came about 300,000 years before the mass
extinction.

The latest evidence came last year from an expedition by an
international team of scientists who drilled 1,511 meters into the
Chicxulub crater looking for definitive evidence of its size and
age. Although interpretations of the drilling samples vary, Keller
contends that the results contradict nearly every established
assumption about Chicxulub and confirm that the Cretaceous period
persisted for 300,000 years after the impact. In addition, the
Chicxulub crater appears to be much smaller than originally thought
-- less than 120 kilometers in diameter compared with the original
estimates of 180 to 300 kilometers.

Keller and colleagues are now studying the effects of powerful
volcanic eruptions that began more than 500,000 years before the
K/T boundary and caused a period of global warming. At sites in the
Indian Ocean, Madagascar, Israel and Egypt, they are finding
evidence that volcanism caused biotic stress almost as severe as
the K/T mass extinction itself. These results suggest that asteroid
impacts and volcanism may be hard to distinguish based on their
effects on plant and animal life and that the K/T mass extinction
could be the result of both, said Keller.

Note: A longer version of this news release appeared in the
Princeton Weekly Bulletin:

http://www.princeton.edu/pr/pwb/03/0922/

============
(2) WHAT KILLED THE DINOSAURS? GERTA KELLY REKINDLES K/T CONTROVERSY

Princeton University Weekly Bulletin, 25 Sept. 2003
http://www.princeton.edu/pr/pwb/03/0922/

Dinosaur dust-up: Princeton paleontologist produces evidence for new theory on extinction
By Steven Schultz

Princeton NJ -- As a paleontologist, Gerta Keller has studied many aspects of the history of life on Earth. But the question capturing her attention lately is one so basic it has passed the lips of generations of 6-year-olds: What killed the dinosaurs?
  
The answers she has been uncovering for the last decade have stirred an adult-sized debate that puts Keller at odds with many scientists who study the question. Keller, a professor in Princeton's Department of Geosciences, is among a minority of scientists who believe that the story of the dinosaurs' demise is much more complicated than the familiar and dominant theory that a single asteroid hit Earth 65 million years ago and caused a mass extinction.

Keller and a growing number of colleagues around the world are turning up evidence that, rather than a single event, an intensive period of volcanic eruptions as well as a series of asteroid impacts are likely to have stressed the world ecosystem to the breaking point. Although an asteroid or comet probably struck Earth at the time of the dinosaur extinction, it most likely was, as Keller says, "the straw that broke the camel's back" and not the sole cause.

Perhaps more controversially, Keller and colleagues contend that the "straw" -- that final impact -- is probably not what most scientists believe it is. For more than a decade, the prevailing theory has centered on a massive impact crater in Mexico. In 1990, scientists proposed that the Chicxulub crater, as it became known, was the remnant of the fateful dinosaur-killing event and that theory has since become dogma.

Keller has accumulated evidence, including results released this year, suggesting that the Chicxulub crater probably did not coincide with the dinosaur extinction. Instead, the impact that caused the Chicxulub crater was likely smaller than originally believed and probably occurred 300,000 years before the mass extinction. The final dinosaur-killer probably struck Earth somewhere else and remains undiscovered, said Keller.

These views have not made Keller a popular figure at meteorite impact meetings. "For a long time she's been in a very uncomfortable minority," said Vincent Courtillot, a geological physicist at Université Paris 7. The view that there was anything more than a single impact at work in the mass extinction of 65 million years ago "has been battered meeting after meeting by a majority of very renowned scientists," said Courtillot.

The implications of Keller's ideas extend beyond the downfall of ankylosaurus and company. Reviving an emphasis on volcanism, which was the leading hypothesis before the asteroid theory, could influence the way scientists think about the Earth's many episodes of greenhouse warming, which mostly have been caused by periods of volcanic eruptions. In addition, if the majority of scientists eventually reduce their estimates of the damage done by a single asteroid, that shift in thinking could influence the current-day debate on how much attention should be given to tracking and diverting Earth-bound asteroids and comets in the future.

Working back in time

Unlike many children today who lap up a steady diet of dinosaur-related books, toys and television programs, Keller knew nothing of the creatures when growing up in Liechtenstein and Switzerland. She became interested in paleontology in the 1970s as a graduate student in earth sciences at Stanford University and began studying the periodic episodes of extinctions and abrupt climate changes that punctuate Earth's 4 billion years.

"I am interested in major events in Earth's history," said Keller. "How did they change life on Earth? What caused the big changes in evolution?"

Keller does not work with big fossils such as dinosaur bones commonly associated with paleontology. Instead, her expertise is in one-celled organisms, called foraminifera, which pervade the oceans and evolved rapidly through geologic periods. Some species exist for only a couple hundred thousand years before others replace them, so the fossil remains of short-lived species constitute a timeline by which surrounding geologic features can be dated.

Princeton geophysicist Jason Morgan said Keller's detailed analysis of these microorganisms gives her work real credibility. "It's not like finding an isolated dinosaur bone," said Morgan. "You have thousands of organisms in a single sample. You can do real statistics on them."

Keller first used fossilized foraminifera to study climate changes in the last several hundred thousand years. Then, going to work for the U.S. Geological Survey, she became interested in earlier periods and began working her way backward in time. "I'm now down to 100 million years and can't go much further," she said, noting that these microorganism records extend back only about 200 million years.

The time of the dinosaur extinction is known as the Cretaceous-Tertiary boundary, or K/T for short. In addition to dinosaurs, many other forms of life were wiped out, including all tropical and subtropical species of foraminifera. Looking at ocean sediments from before and after the K/T boundary "is like day and night," Keller said, because so much life disappeared.

At many locations around the world, the K/T boundary is clearly visible in rock formations, which contain a thin layer of clay rich in the element iridium. Because iridium is more common in asteroids and comets than on Earth, scientists, led by father and son Luis and Walter Alvarez, proposed in l980 that an asteroid or comet must have struck Earth just at the K/T boundary. When the Chicxulub impact crater was discovered in 1990, it appeared to be a likely source for the iridium and seemed to confirm the hypothesis.

Several lines of evidence

Keller began studying the K/T boundary several years after coming to Princeton in 1984 and soon suspected that the story might not be so straightforward. In a series of field trips to Mexico and other parts of the world, she has accumulated several lines of evidence. She has found, for example, populations of pre-K/T foraminifera that lived on top of the impact fallout from Chicxulub. (The fallout is visible as a layer of glassy beads of molten rock that rained down after the impact.) These fossils indicate that this impact came about 300,000 years before the mass extinction.

In other studies spread across a range of excavation sites, Keller has found evidence that the ecological disruption caused by the Chicxulub impact may not have been as severe as originally thought. She found normal marine sediments lying directly on top of the fallout layer, suggesting that there were no tsunami waves or other major disturbances.

In addition, Keller and her students conducted studies throughout Mexico, Guatemala and Haiti (see related story below) that revealed signs of as many as three meteorite impacts: the Chicxulub impact, evidenced by the fallout of glass beads; the K/T impact with its iridium layer and mass extinction; and probably a third smaller impact, evidenced by another iridium layer about 100,000 years after the mass extinction.

The latest evidence came last year from an expedition by an international team of scientists who drilled 1,511 meters into the Chicxulub crater looking for definitive evidence of its size and age. Although interpretations of the drilling samples vary, Keller contends that the results contradict nearly every established assumption about Chicxulub and confirm that the Cretaceous period persisted for 300,000 years after the impact. In addition, the Chicxulub crater appears to be much smaller than originally thought -- less than 120 kilometers in diameter compared with the original estimates of 180 to 300 kilometers.

Keller and colleagues are now studying the effects of powerful volcanic eruptions that began more than 500,000 years before the K/T boundary and caused a period of global warming. At sites in the Indian Ocean, Madagascar, Israel and Egypt, they are finding evidence that volcanism caused biotic stress almost as severe as the K/T mass extinction itself. These results suggest that asteroid impacts and volcanism may be hard to distinguish based on their effects on plant and animal life and that the K/T mass extinction could be the result of both, said Keller.

Softening opposition

Because her results are among the first to quantify the biotic effects of volcanism, they may also help other scientists understand the likely effects of greenhouse warming resulting from volcanism or other causes, Keller said.

Together Keller's results give her hope that her ideas may gain greater recognition, but she remains cautious about how many people she is likely to convince. "When you have such a large group of scientists who became famous based on the idea that a single impact at Chicxulub caused the K/T mass extinction, you can't easily change their minds," she said.

Courtillot, whose views largely concur with Keller's, is optimistic that the opposition may be softening, particularly concerning the role of volcanism in the K/T extinction. "Recent years are vindicating our minority views -- at least I hope that is the case," he said.

In the meantime, Keller has further studies planned, including trips to extract sediments from Brazil, the Indian Ocean and the Middle East. She hopes these samples could broaden and clarify the story of the last days of the dinosaurs. "We want to nail it down as far away from Chicxulub as possible," she said.

===========
(3) I'VE GOT A BONE TO PICK WITH YOU, SAY FEUDING DINOSAUR EXPERTS

The Observer, 7 Sept. 2003
http://observer.guardian.co.uk/international/story/0,6903,1037002,00.html

Robin McKie, science editor

The world's biggest bang wiped out the dinosaurs in a cataclysm that swathed our planet in choking dust - or at least that is what many palaeontologists claim. Others say dinosaurs died out gradually as Earth's climate and geology changed.

It sounds a typical academic dispute - but last week it erupted into open warfare. Allegations have been made of deceit and unethical behaviour. One scientist is even alleged to have held back inconvenient evidence.

'This affair has become an object lesson on how partisan and unethical the whole dinosaur controversy has become,' said Dr Norman MacLeod, keeper of palaeontology at London's Natural History Museum. 'Young scientists are now refusing to get involved in this field because no matter what they say it will offend someone and dam age their careers. It's like the nature-nurture debate. No matter what you say, someone will hate you for it.'

The furore focuses on a massive drilling project set up to study the Chicxulub crater in Yucatán. Buried under half a mile of rock, the crater was created 65 million years ago when Earth was hit by a meteorite 10 miles in diameter. The blast would have blotted out the sun for decades, or even centuries, many researchers claim. Given that around this time the dinosaurs became extinct, many scientists made a direct link. Denied sunlight and food, most of the world's animals would have starved, and choked, to death.

But others disagree. Volcanoes, global warming or sea level changes were responsible, they say - pointing to evidence that most dinosaurs became extinct before the explosion and to the fact that many large animals such as alligators survived this alleged catastrophe. Things weren't that bad, they say.

In a bid to resolve the dispute, a £2 million project was launched in Yucatán two years ago. Researchers drilled a pipe into the Earth's crust to bring back samples of the meteor and crater wall. By studying what happened just before and just after the meteorite impact, scientists would glean critical insights, it was argued. For example, it would show if all life was extinguished in the millennia that followed the impact.

In 2002 the first samples were brought up. To the disgust of Mexican geologists, and to many scientists who doubted the Big Blast theory, these were entrusted to Jan Smit, a geologist at the Free University of Amsterdam and a leading supporter of the meteorite hypothesis. Promising to cut up the samples and distribute them to project scientists, Smit left with the precious Chicxulub remains. A year later, many scientists were still seeking the promised samples. 'We were dismayed,' geochemist Erika Elswick of Indiana University in Bloomington states in the current issue of Nature . 'There was no explanation given, no apology.'

Eventually some samples were sent out, but most were too small for experiments. Dismay turned to fury. Researcher Gerta Keller, of Princeton University, pressed Smit and at last got a good set of samples. At the European Union of Geosciences conference in Nice, she presented her results, which were a bombshell. Her research, Keller claimed, clearly showed that marine plankton, far from being killed off by debris blotting out the sun, thrived for hundreds of thousands of years after the crater was created. The meteor that struck at Chicxulub was not responsible for mass extinctions, she concluded.

Nor is Keller reticent in her interpretation of Smit's behaviour. 'He tried to postpone our results so that he could remain unchallenged at that meeting,' she states in Nature . Smit dismisses the allegation as 'ridiculous'. He blames the delays on his busy schedule and poor communications by those running the project. He also claims Keller misidentified some fossils in her samples.

The row is far from over. Project scientists are preparing papers containing results of studies of the samples they obtained from Smit and these will be published in a special issue of Meteoritics and Planetary Science next year. Few doubt it will resolve the issue. As MacLeod says: 'It's no longer about science. It's about reputations.'

Copyright 2003, The Observer

=========
(4) NEW EARLY PROTEROZOIC MEGA-IMPACT FALLOUT UNIT, PILBARA CRATON

Andrew Glikson <geospec@webone.com.au>

DS7 - a new asteroid impact fallout unit, Dales Gorge Iron Member (2.47-2.50 Ga),
Brockman Iron Formation, Hamersley Group, Pilbara Craton, Western Australia

Andrew Glikson
Research School of Earth Science, Australian National University,
Canberra, A.C.T., 0200
    
This preliminary note reports the discovery and summary documentation of a <5 cm-thick
microkrystite-bearing impact fallout unit associated with the Shale Macroband No. 7 of
the Dales Gorge Iron Member (DSM), Brockman Iron Formation, Hamersley Group, Pilbara Craton.
Age constraints on the DSM are defined as 2.47-2.50 Ga (A.F. Trendall, pers. comm., 2003)

DS4 spherules were originally regarded as pyroclastic in origin (La Berge, 1966). Trendall
and Blockley (1970, p.114) remark on "coarsely clastic breccias in the S4 and S7 Macrobands".
At Dales Gorge, below Fortescue Falls, exposure of low dipping (~10o) strata allow detailed
observations on Macroband units DS2 to DS11 intercalated with banded iron formation (BIF) of
the Dales Gorge Member. At type location 50K 0659620E7513547N the DS7 Shale Macroband unit
consists of about 50-60 cm-thick stilpnomelane-dominated tuffaceous sediment containing
a ~<5 cm-thick microkrystite spherule-rich unit composed of  ~<1 mm-diameter stilpnomelane
spherules in part mantled by K-feldspar and set in stilpnomelane-rich matrix.

The DS7 unit is similar in most respects to, although thinner than, DS4 microkrystite spherule
impact unit. The lack of shocked quartz detritus suggests simatic crustal source regions of
the impact ejecta (Simonson et al., 1998). Iridium and Platinum anomalies in DS4 and the
size distribution of microkrystites (<1.7 mm mean diameter) allow estimates of the diameter
of the parent asteroid in the order of several tens of kilometer and of the parent crater on
the scale of several hundred kilometers (Glikson and Vickers, 2003).

DS7 is the 16th Precambrian impact fallout unit recorded to date (including 2 multiple impacts).
Being the 2nd impact unit found in the Dales Gorge Iron Member, a renewed search for impact
units intercalated in the BIF is warranted, in order to elucidate (1) the impact history of
these impact units; (2) potential relations between impacts and volcanic activity; (3) nature
and origin of associated stilpnomelane-rich tuffaceous sediments. Potential relations between
the multiple DS impacts, banded iron formation and stilpnomelane-rich tuffaceous units remain
open questions. Further detailed field mapping of DS7 and a search for new impact units are
planned.

References: Glikson, A.Y. and Vickers, J., 2003.  Archaean to early Proterozoic asteroid impact
fallout units and related tsunami deposits, Pilbara Craton, Western Australia. Geological
Survey of Western Australia Report; La Berge, G.L., 1966. Altered pyroclastic rocks from iron
formation in the Hamersley Basin, Western Australia. Econ. Geol., 11, 147-161; Simonson,
B.M. 1992. Geological evidence for an early Precambrian microtektite strewn field in the
Hamersley Basin of Western Australia, Geological  Society America Bulletin 104, 829-839;
Simonson, B.M., Davies, D., Wallace, M., Reeves, S. and Hassler, S.W., 1998, Iridium anomaly
but no shocked quartz from Late Archean microkrystite layer:  oceanic impact ejecta?:  Geology,
26, 195-198;  Trendall, A.F. and Blockley, J.G., 1970. The iron formations of the Precambrian
Hamersley Group, Western Australia. Geological Survey of Western Australia Bulletin, 119,
365 pp.

===========
(5) SPACE ROCK'S CLOSE CALL

BBC News Online, 24 Sept. 2003 
http://news.bbc.co.uk/1/hi/sci/tech/3133000.stm

By Dr David Whitehouse
BBC News Online science editor 

A small rock about five metres across flew past the Earth a few days ago. Only four other such celestial bodies have come closer since monitoring began.
 
The rock, designated 2003 SW130, was far too small to pose any risk. Had it entered the Earth's atmosphere, it would have fragmented in a spectacular meteor display.

But its detection demonstrates just how efficient astronomers are becoming at picking up such rocks, even those that are the size of a living room.

Half of the top 10 approaches to the Earth by space rocks have been detected in the past two years.

From Venus to the Earth

The rock was discovered about 21 hours after its closest approach by Arianna Glearson and Tom Gehrels observing with the Spacewatch 1.8-metre telescope in Arizona, US.

The following night, the Klet Observatory in the Czech Republic picked it up. It was almost obscured by the glare of Mars which was nearby in the sky.

Observations suggest that it came within about 168,000 kilometres of the Earth at 0600 GMT on 19 September.

It has an orbit that takes it from just inside the orbit of Venus to just outside the orbit of the Earth.

Astronomers are becoming increasingly efficient at detecting small rocks moving in the Earth's vicinity. Last year, they found 2002 XV90 and 2002 MN, which occupy number two and three in the list of close approaches by celestial objects.

'Lots of them'

The closest known approach was 1994 XM1, which came within 112,000 km.

Of course, many large objects do strike the Earth from time to time, such as the Tunguska impactor in 1908.

Brian Marsden, of the Minor Planet Center in the US, said: "There must be lots of objects as tiny as 2003 SW130 that pass closer than the Moon and are missed.

"Spacewatch did a great job finding it, and the Klet Observatory in following it up. Nice cooperation - even if the object would likely burn up high in the atmosphere if it were to hit," he told BBC News Online.

Copyright 2003, BBC

=========
(6) THE DISCOVERY OF 2003 SW130

The Spacewatch Project, 25 Sept. 2003
http://spacewatch.lpl.arizona.edu/new.html

2003 September 20- To date, 2003 SW130 is the smallest asteroid detected by Spacewatch and designated by the MPC. During a routine survey scan at the Spacewatch 1.8-meter telescope, sweeping the sky for asteroids, Arianna E. Gleason noticed a significantly trailed object. Excited by the prospects of finding this Fast-Moving Object [FMO] and the implication of its Near-Earth Asteroid [NEA] status she hurried to execute a series of follow-up measurements and gave the object a Spacewatch designation of ts272. This designation name corresponds to the "Third Spacewatch" survey making its 272nd designation.

Over a period of 3 nights, she and fellow Spacewatch observer, Prof. Tom Gehrels, re-observed this object numerous times. More measurements were obtained by observers at the Klet Observatory-KLENOT and the Very Large Telescope [VLT]. Re-observation is necessary to produce an orbit solution for NEA candidates. A preliminary orbit calculated by the Minor Planet Center [MPC] suggested this Spacewatch object was only 0.005 astronomical units [AU] (750,000km) from the Earth at the time of discovery, or about twice the distance from the Earth to the Moon. This NEA's closest approach actually occurred the night before, September 19 when it flew by at a distance of only 162,000km, or less than half the distance to the Moon! It was not visible until September 20, however, since it had been inside of Earth's orbit, only visible in the daytime sky until after its closest approach.

Subsequent observations of this tiny asteroid were a bit tricky for the Spacewatch observers. On the second night Ms. Gleason acquired follow-up measurements, the length of the trail had decreased to 1/4 its original size! What could account for this change? The object's apparent angular rate was slowing down. In other words, as an object travels farther away from the Earth its apparent motion on the sky decreases, manifesting in Spacewatch images as a decrease in trail length. Prof. Gehrels's follow-up observations also showed the trail length shrinking as it continued to recede from the Earth. The change in trail length from 73 arcsec to 3 arcsec is a function of decreasing apparent angular rate. The actual velocity (9.2km/s) of this object has not changed significantly. In addition to this drastic change in trail length overnight, the object's location was always quite far off the ephemeris prediction. A bit of hunting around the sky was required by Ms. Gleason and Prof. Gehrels to make follow-up measurements, now complicated by both the location and the expected trail length being in question.

Fortunately, enough data were acquired to establish a reliable orbit and on Sept 22, this Spacewatch object was given the official designation of 2003 SW130 which is an Aten-type asteroid. By definition, an Aten is an asteroid with a semi-major axis less than 1 AU, whose orbit crosses that of Earth near its aphelion, or farthest point from the Sun.

As the smallest asteroid detected by Spacewatch and designated by the MPC, its estimated size is between 5 - 9 meters in diameter, calculated as a function its absolute magnitude (H = 29.2), An object of this size poses no threat to the Earth, despite its close proximity on Sept 19. If the orbit were ever perturbed, predicting an impact with the Earth, it would probably disintegrate in the Earth's upper-atmosphere, appearing as 'shooting-stars'. Small pieces of the asteroid might also fall to the ground as meteorites. It has been roughly calculated that objects of this size (about 5 meters) impact somewhere on the Earth's surface once each month! These are the largest objects a person could expect to see as a brilliant shooting-star in a lifetime. Although the smaller objects such as 2003 SW130 are not hazardous, the statistics of their population provide information about the processes of fragmentation and cohesion of asteroids due to their mutual collisions and gravitation, respectively.

2003 June 7- Comet C/2003 L1 (SCOTTI) discovered by J. V. Scotti.
2003 March 10 - Amor Asteroid 2003 EN16 becomes the first NEO discovered with the Spacewatch Mosaic of CCDs.
2003 - Comet C/2003 A2 discovered January 10th by A. E. Gleason.
2002 - Photo Gallery of the 0.9-meter telescope conversion.
2002 October 23 - First Observation of an NEO with the Mosaic! On the second night of testing the CCD mosaic in bright moonlight, the focus and collimation were already so good that we decided to try some real observations. We detected the Potentially Hazardous Asteroid (PHA) 2002 TD66. Software and engineering refinements continue.
2002 October 22 - First Light on the Mosaic of CCDs! On Oct. 10 we had First Light on the optical system, and now we have achieved First Light on our new science detector, the Mosaic of CCDs. Focus, tip, and tilt look good.
2002 October 10 - First Light on the Mosaic optical system. Installation of the new optical system for the mosaic of CCDs was completed, and images of star trails on a small engineering CCD showed good collimation and focus. Tracked "stare" images will be next, after the telescope is balanced with the science detector and the drive system set up again.
2002 September 24 - Spacewatch accepts delivery of the Mosaic mirror and conversion of the telescope speeds ahead.
2002 August 16 - Spacewatch detection of "lost" CONTOUR Spacecraft. [More]

=========== LETTERS ===========

(7) THOUGHTS ON IMPACT RISK ASSESSMENT

Gerrit Verschuur <gverschr@postoffice.memphis.edu>

Those of us who carry out research in whatever field would not dream of making public our every thought and premature conclusion about the outcome or meaning of an experiment. We make our observations and then try to understand them. While you might be momentarily excited by finding something new, any good scientist continues to see whether the phenomenon persists. Subsequently you sit down and analyze the data in the rarefied atmosphere of your office. If you are working in a team you will have discussions as you try to determine what makes sense and what does not. None of that is published.

During this process you will consider many ideas that are quickly rejected. Now just imagine that you were to publish them all. You'd become a laughing stock! A former colleague and I used to say that bright new ideas had "half-lives." If you still liked it a few days or weeks later you might be onto something. A few months later you might be convinced to the point that you would write it up for publication. However, the vast majority of such ideas are dead within a day or two.

To me it is inconceivable that there should be any branch of science where first impressions about the meaning of one's data are published. That is why the entire concept of the Torino scale makes no sense to me. That is like asking me to publish any passing thought I may have about my experiments. Something has got to change.

I'd begin by changing the numbers used as flags on any impact risk scale. Instead of running from 1 to 10 assign numbers from 0.1 to 1. The point is that if a journalist (no slight intended) sees that as asteroid is assigned a threat scale of 1 that suggests a certain hit. However, if it is assigned a number like 0.1 no one will get disturbed. That will allow all the other decimal places to be used for refining the scale before the top of the scale is reached

For example, 0.1 might indicate that more observations are desirable, when you can get around to it. Something around 0.5 might signal that more observations are urgently needed. Then I'd use 1.0 on the scale to indicate absolute certainty of collision but producing only regional destruction. I'd go so far as to suggest that any numbers above 1.0 be used to indicate the extent of the damage. Thus 1.5 could imply the collapse of civilization and 2.0 would mean extinction of life.

The scale could also be refined so that we allow for the time interval before possible impact. If an asteroid appears on a collision course in one year it would be assigned a higher decimal number to urge immediate follow-up observations. If it doesn't pose a threat for decades than a lower decimal number of appropriate because there is no urgency for follow-up data.

Whatever the details of any change I will repeat that the casual observer seeing that an impact risk has been assessed as a 1 will assume it is certain. In every other walk of life a probability of 1 is certainty. So let's remove that psychological barrier to understanding a risk scale. No one will get excited to see an 0.1 on the NEO impact risk web page.

Gerrit Verschuur

==========
(8) FORECAST OF A BIG EARTHQUAKE AND NEO COLLISION ALERTS

Syuzo Isobe <isobesz@cc.nao.ac.jp>
Japan Spaceguard Association

Dear CCNet Colleagues:

As posted in CCNet of September 6, a Japanese amateur stronomer predicted that a big
earthquake with magnitude 7 would hit the Tokyo area between September 14 to 18.
I knew this information through a popular magagine published on September 8 and a
circular through an academic e-mail by Dr. Arima (past minister of Education, Science,
and Culture) and Dr. Ueda (Emeris Professor of University of Tokyo and Geophysisit)
who called a workshop on this topic inviting Mr. Kushida on September 13.

Although I read his aricles on his VHF observatons, I can not find any physical
support on his forcast. Therefore, I dared to stay in the Tokyo area between
September 14 to 18 to show my attitude that I did not believe this forcast. We had one
earthquake with magnitue 4 which he said is too weak to detect its pre-activity, on
September 20 in an area of the outer edge of his estimated fan-shaped zone.

I can make a simple calculation of probability of a big earthquake in the Tokyo area.
We have one big earthquake with magnitude larger than 7 once one to two hundred years.
This interval is about 50,000 days. His possible days are between 14 to 18, that is 5 days.
Then, even if one says that any date will be possible to have a big earthquake, its
success probability is one to 50,000. Even though nearly 30 million people surrounding the
Tokyo are living, working, and enjoying their life without any anxious for that big earthquake.

Now, I would like to question why the NEO community put out an asteroid alert with a
collision probability of 1 to 1,000,000. On this point, I strongly support Alain Maury's
recent propsal and Brian Marsden's. We should handle NEO collision alerts much more
carefully. As I wrote in my COSPAR paper, the probability will vary drastically if one can
extent our target NEO observational period, and in nearly all cases it will go down to zero.
I believe this is minimum actions which do not create unnecessary confusion to mass media and public.

Syuzo Isobe

===========
(9) K/T CONTROVERSY: WE SHOULD BE OPEN TO NEW SCIENTIFIC EVIDENCE

Michael E. Phillips <Michael.Phillips@geog.uib.no>

Benny,

I'm sure you have this story already, if so my apologies.

It's certainly food for thought, as Chicxulub has long been held up as the imapct that
finally finished the dinosaurs, or worse still, the only reason. I have never agreed with
the anti-impact/pro-volcanism theorists that base their findings on lack of impact evidence
associated with mass extinctions, as that says what is says - we haven't found the evidence
(yet). I feel I'm in a majority in the Geoscience world when I say that the general view is
that the K/T extinction was a combination of factors, including impact(s), volcanism and other environmental considerations.

So in that respect, Gerta Keller isn't saying anything new. However, if the evidence suggests
that Chicxulub did not occur at the K/T event, that's a different story and whilst I call
myself a 'pro-impact' believer, ultimately it's the scientific results that matter.

So Gerta Keller certainly deserves to be heard, she could be onto something!

Michael Phillips
Institute for Geography
University of Bergen
Breiviksveien 40
5045 Bergen

tlf. +47 55959974
michael.phillips@geog.uib.no

====
(10) "NEW THEORY ON DINOSAUR EXTINCTION": SLOPPY PRESS RELEASE

From: Michael Paine <mpaine@tpg.com.au>
To: sschultz@princeton.edu

Steven
http://www.princeton.edu/pr/news/03/q3/0925-keller.htm
That is a very sloppy press release for a university. The idea of a
gradual rather than sudden extinction is far from a "New theory". As you
point out later in the article, the debate has been going on for decades.
There is an excellent review of the issues by Walter Alvarez in
Astrobiology  Vol 3 No.1 p153
(http://giorgio.ingentaselect.com/vl=3114634/cl=53/nw=1/rpsv/catchword/mal/15311074/v3n1/s11/p153

I have kept track of the healthy debate at
http://www4.tpg.com.au/users/horsts/crater.html

I take issue, however, with the statement "In addition, if the majority
of scientists eventually reduce their estimates of the damage done by a
single asteroid, that shift in thinking could influence the current-day
debate on how much attention should be given to tracking and diverting
Earth-bound asteroids and comets in the future."

This is the sort of careless line that politicians sieze on to undermine
  legitimate concern expressed by scientists.

Spaceguard (which receives pitiful funding, mostly from the USA) is
attempting to find most Near Earth Asteroids that are around  1km in
diameter since an impact around this size could easily cause the
collapse of our civilisation (eg a year with summer). The annual risk of
such an impact is about one in a million, compared with 1 in 100 million
for objects capable of causing mass extinction so debate over Chicxulub
has very little to do with the need to track NEAs. See a paper about the
consequences of smaller impacts at
http://www4.tpg.com.au/users/horsts/bioastr2002.pdf

While there might be uncertainy about the size of the Chicxulub crater
it should be remembered that it was the worldwide evidence of a major
impact that led to the theory that an asteroid or comet killed the
dinosaurs. That evidence led to estimates of the magnitude of the impact
well before a crater was discovered. Since then super-computer modelling
has confirmed global environmental damage caused by major impacts. See
http://www4.tpg.com.au/users/horsts/climate.htm
for a summary and links.

There are many other natural hazards that could ruin our day as a
species - volcanic explosions, flood basalts, supernova, ice ages, gamma
ray bursts. The key point about a major asteroid impact is that, with
comparatively little effort and cost, the impact can be predicted and
mitigating action taken. We have the technology to do this now.

regards
Michael Paine

=============
(12) AIAA PLANETARY DEFENSE CONFERENCE (PDC) PROGRAM AND NASA SMALL NEO HUNT

Andy Smith <astrosafe22000@yahoo.com>

Hello Benny and CCNet,

The PDC Program is now on the Web at
http://www.aiaa.org/calendar/index.hfm?cal=5&programSeevie...
and there is a separate click for each day (23-26 Feb.
04). It is impressive in both scope and depth...and it
is good to see such a high level of international
participation. It is also good to see that Congressman
Rohrabacher will make the opening keynote
presentation, because he has been such a strong
supporter of PD.

Thanks to the CCNet, we have an international and open
place for dialogue on such important matters as this
and it is possible to share technical, calendar and
other information.

NASA Small NEO Hunt Report

This impressive report is at
http://neo.jpl.nasa.gov/neo/neoreport030825.pdf

It certainly reflects a lot of effort, in a short
period of time, and it outlines the important work and
support that is needed....to find the large number of
sub-kilometer NEO.

However, we felt that this important  effort should
have given more attention to the many ongoing and
promising programs which aim at helping to complete
the critical NEO inventory (100,000 plus objects) in a
decade or so. Some of these programs are developing
better ground systems (Pan-STARRS, LSST and others)
and some are developing orbital systems (GAIA,
Sub-millimetron, etc..). We hope the development and
operation of the next generation of NEO telscopes will
reflect a high level of global technical
teamwork....and we would certainly like to see the
promised 3-meter UK telescope play a major role
(recent comment by BP).

We also thought the study seriously underestimated the
consequences of sudden climate change (the famine
fatalities from the 1815 volcanic explosion were
probably close to a million, in Ireland alone....and
this explosive energy level was about what would
result from  a 200 meter NEO impact). Also, Vitimsky
(probably about a 6 meter atmospheric impact,  in
Siberia, last September) showed us that we need to
move the 50 meter bar down a bit.

It is great to see such important documents as the
NASA  study being provided on the Web and we urge the
PDC team to also do this, if at all possible. We are
also looking forward to a web page from the Russian
Planetary Defense Center and our friends who are
developing the Citadel system (participating in PDC
Session 10).

Cheers,
Andy Smith
International Planetary Protection Alliance (IPPA)
astrosafe22000@yahoo.com

============
(13) AND FINALLY: FORGET ASTEROIDS, GAMMA RAYS MAY HAVE DEVASTATED LIFE ON EARTH

New Scientist, 24 Sept. 2003
http://www.newscientist.com/news/news.jsp?id=ns99994198
 
A devastating burst of gamma rays may have caused one of Earth's worst mass extinctions,
443 million years ago.

A team of astrophysicists and palaeontologists says the pattern of trilobite extinctions at that time resembles the expected effects of a nearby gamma-ray burst (GRB). Although other experts have greeted the idea with some scepticism, most agree that it deserves further investigation.

GRBs are the most powerful explosions known. As giant stars collapse into black holes at the end of their lives, they fire incredibly intense pulses of gamma rays from their poles that can be detected even from across the universe for 10 seconds or so.
  
Doomsday Scenario

All the bursts astronomers have recorded so far have come from distant galaxies and been harmless on the ground, but if one occurred within our galaxy and was aimed straight at us, the effects could be devastating, according to astrophysicist Adrian Melott of the University of Kansas in Lawrence.

The Earth's atmosphere would soak up most of the gamma rays, Melott says, but their energy would rip apart nitrogen and oxygen molecules, creating a witch's brew of nitrogen oxides, especially the toxic brown gas nitrogen dioxide that colours photochemical smog (see graphic).

Melott estimates that a burst would produce enough of the gas to darken the sky, blotting out half the visible sunlight reaching the Earth. Nitrogen dioxide would also destroy the ozone layer, exposing surface life to a dangerous overdose of ultraviolet radiation from the sun for a year or more until the ozone recovered.

Plankton layer

The idea that GRBs could have affected the course of evolution was first suggested two years ago (New Scientist print edition, 15 December 2001, p 10). John Scalo and Craig Wheeler of the University of Texas at Austin estimated that GRBs close enough to affect life in some way might occur once every five million years or so - around a thousand times since life began.

Now Melott believes he has palaeontological evidence that this actually happened at the end of the Ordovician period 443 million years ago, causing one of the five largest extinctions of the past 500 million years. Working with Bruce Lieberman, a specialist in fossil trilobites also at the University of Kansas, and other colleagues, he looked at the pattern of extinctions in the late Ordovician.

The researchers found that species of trilobite that spent some of their lives in the plankton layer near the ocean surface were much harder hit than deep-water dwellers, which tended to stay put within quite restricted areas. Usually it is the more widely spread species that fare better in extinctions.

Melott says this unusual pattern could be explained by a GRB, which would probably devastate creatures living on land and near the ocean surface, but leave deep-sea creatures relatively unharmed.

Previous theories blame the two extinctions that occurred in the late Ordovician period on the start and end of an ice age at the time. But it is hard to explain what triggered the ice age itself, which started very suddenly at a time when the climate was quite warm.

Continental changes would have taken too long, and climate models have not been able to replicate the ice age. But a GRB that blocked out the sun could have caused it, points out Pat Brenchley, a retired palaeoecologist from the University of Liverpool, UK, calling the idea "an interesting alternative".

"I'd like to see a lot more information," says Peter Sheehan of the Milwaukee Public Museum, who has studied the Ordovician extinctions. When Sheehan looked at the pattern of extinctions among brachiopod species, he found that 90 per cent of the widespread species survived, compared with only 10 per cent of those living in restricted areas. This is the normal pattern during extinctions.

He thinks that glaciation alone might have killed off shallow-water species by draining water from shallow continental seas. Mellot concedes that a lot more work needs to be done, but is optimistic: "We think it's a good hypothesis."
 
Jeff Hecht

Copyright 2003, New Scientist

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