PLEASE NOTE:


*

CCNet, 24/2000 - 25 February 2000
---------------------------------


(1) ADDING UP THE RISKS OF COSMIC IMPACT:
    RESEARCHERS TURN ATTENTION TO SMALLER, MORE FREQUENT BLASTS 
    MSNBC Space News, 24 February 2000

(2) NATIVE AMERICAN TRIBE DEMANDS RETURN OF METEORITE
    Larry Klaes <lklaes@BBN.COM>

(3) BETWEEN GLOBAL WARMING & ICE AGE WARNING: WE STILL DON'T UNDERSTAND 
    PERIODIC CLIMATE CHANGE
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(4) ASTEROID 2000 BF19 AND THE MEDIA
    Daniel Fischer <dfischer@astro.uni-bonn.de>
   
==========                 
(1) ADDING UP THE RISKS OF COSMIC IMPACT:
    RESEARCHERS TURN ATTENTION TO SMALLER, MORE FREQUENT BLASTS 
  
From MSNBC Space News, 24 February 2000
http://www.msnbc.com/news/373938.asp

By Alan Boyle
MSNBC
 
Feb. 24 -  Many scientists believe an asteroid or comet killed off the
dinosaurs, but the impact of cosmic collisions on human history is a
matter of sharper controversy. Some researchers say computer simulations
and historical reviews may shed new light on how common such impacts
were in the past - and how much of a threat they could pose in the
future.   

IN RECENT YEARS, most of the concern about cosmic threats has focused on
the hundreds of space rocks and iceballs bigger than 0.6 miles (1
kilometer) in diameter that have a chance of someday colliding with
Earth. Scientists say objects that size could hit with the force of
hundreds of hydrogen bombs, having a global environmental impact and
potentially killing off whole species.

NASA estimates that such collisions occur every 100,000 to 1 million
years, based on analyses of lunar impacts going back to the early 1980s,
said David Morrison, who heads the astrobiology and space research
directorate of NASA's Ames Research Center.

"There is no 'theory' involved," he told MSNBC. The figures are based on
observations of crater densities on the moon, estimates of the current
number of near-Earth objects and the assumption that the average impact
rates have held steady over time.

These figures account for near-Earth objects as big as the one that
scientists say hit Mexico's Yucatan coast 65 million years ago, leading
to the demise of the dinosaurs. But they don't include less deadly
objects much smaller than a kilometer in width.
      
"The short-term threat is more from the smaller objects than the larger
objects," said Benny J. Peiser, an anthropologist at Liverpool John
Moores University who specializes in the social implications of the
asteroid/comet threat.  
 
A computer simulation indicated that more than 1,000 fatal impacts could
crop up in a 100,000-year period, Peiser said last week in Washington
during the annual meeting of the American Association for the
Advancement of Science.

The computer software, devised by the University of Arizona's John Lewis
and run by Michael Paine of the Planetary Society Australian Volunteers,
generates scenarios based on assumptions about the distribution of
near-Earth objects. Thus, the results shouldn't be taken as predictions
of what would actually happen. However, Peiser said the simulation
pointed up some factors that may not be fully considered in official
risk estimates.
      
WITHOUT A TRACE

Most of the fatal events in the 100,000-year scenario were airbursts
over land, analogous to the 1908 Tunguska Meteorite in Siberia. In that
case, a 60-meter-wide (200-foot-wide) object blew up above a remote
Siberian forest with the force of 15 million tons of TNT.

Other blasts occurred in or above the ocean, setting off tsunami waves
that inundated coastlines. Only 3 percent of the scenario's fatal events
left a crater. "Land craters (on Earth) are therefore a very poor
indicator of the hazard due to comets and asteroids," Peiser said.
      
CASUALTY COUNTS

In this and other long-term scenarios, at least one catastrophic event
turns up. The 100,000-year scenario, for instance, includes the
potential for an impact involving a 3-mile-wide (5-kilometer-wide)
asteroid that touches off a climate catastrophe, wiping out the human
race.  

That "Armageddon" was excluded in figuring out the fatality count for a
typical 10,000-year period - one-tenth the total span for the computer
scenario. Paine and Peiser came up with 13 million deaths traceable to
asteroid or comet impacts, assuming a constant worldwide population of 5
billion.
      
HISTORICAL RECORD

How does this square with human history? Here, science tends to blend
with folklore. For example, in China's Shanxi Province, 10,000 people
were said to have been killed in the year 1490 by a hail of "falling
stones" that some astronomers surmise may have been triggered by the
breakup of a large asteroid.

Bruce Masse, an environmental archaeologist with Los Alamos National
Laboratory, has tried to untangle other astronomical observations from
ancient tales told from the Middle East to Hawaii. He referred to an
impact event in the Rio Cuarto region of northern Argentina, in which an
asteroid 100 to 300 yards (or meters) across apparently skipped along
the surface, leaving a series of gouges.  

This map shows the shallow path of a near-Earth object that blazed
through the atmosphere and hit northern Argentina thousands of years
ago. Archaeologist Bruce Masse says the black spots indicate areas where
cultures told tales of a catastrophic "Great Fire" in ancient times.

This event, which has been dated to around 2000 B.C., may square with
tales told of a catastrophic "Great Fire" by cultures in a large region
around the impact site, Masse said.

Masse went on to say that at least some of the tales of a Great Flood,
found in hundreds of cultures around the world, may relate to an oceanic
impact that set off a tsunami.

"The preliminary picture emerging from this analysis is that on or
shortly after May 10 in 2807 B.C., the earth was struck by a cosmic
impact in the deep waters between Africa and Antarctica. ... These data
indicate that the flood itself was the very real product of a
combination of large tsunami and atmospheric rainout."

Masse cautioned, however, that his analysis was not yet complete. Other
researchers have sought to link the biblical account of a Great Flood to
a catastrophic inundation of the Black Sea, touched off in the wake of
the last Ice Age around 5000 B.C.
      
THE SKY ISN'T FALLING

NASA's Morrison said the linkages between folklore and celestial
phenomena could easily be taken too far. He cited the example of Russian
psychologist Immanuel Velikovsky, who tied all sorts of ancient accounts
to cosmic collisions and near-collisions. "One has to be careful not to
fall into Velikovsky-like situations," Morrison said.

He said the computer simulations were useful for putting the risk of
cosmic impact into perspective, but shouldn't necessarily be taken at
face value. "There's nothing really new in these simulations," Morrison
told MSNBC. "All they do is generate output that's based on what's put
into them ... so what you get generally reflects the assumptions that
you put in."  
 
Even the projected death toll had to be put into perspective, Morrison
said. When compared with total deaths during the same time frame,
impact-related fatalities generally worked out to far fewer than 1 in
10,000, which he said was consistent with the view that asteroids and
comets were a significant but not a major cause of death.

Morrison, who has participated in NASA's 1992 Spaceguard Survey and
other efforts to assess the risk from near-Earth objects, said he was
"quite skeptical" about tying cosmic impacts to historical events.

But Peiser said such events should be considered among the environmental
factors that could affect history. For instance, small-scale impacts -
along with increased levels of cosmic dust in the atmosphere - could
have contributed to climate changes, he said.

"You have to look for something before you find it," he said

------

What do you think about the threat of an asteroid impact?
 
* 43501 responses

The threat is being exaggerated  33%
 
I'm adding it to my list of worries 23%
 
Something needs to be done! Now! 29%
 
None of the above (share your views on the Space News BBS) 15%

Copyright 2000, MSNBC

=======
(2) NATIVE AMERICAN TRIBE DEMANDS RETURN OF METEORITE

From Larry Klaes <lklaes@BBN.COM>

Tribe Demands Return of Meteorite

By JOHN JURGENSEN
.c The Associated Press

NEW YORK (AP) - A group of American Indians says a 16-ton meteorite that
will be the main attraction at the Museum of Natural History's new
planetarium is a holy tribal object and should be returned to Oregon.

The meteorite - about the size of a small car - will be displayed in the
planetarium's main hall when it opens Saturday.

The meteorite hit Earth more than 10,000 years ago and was moved by
glacial ice to a hillside in West Linn, Ore. The Clackamas tribe adopted it
as a sacred object, and the rain water that collected in its deep craters
was prized for its holiness.

``Songs given to us by the meteorite are still sung today,'' said Ryan
Heavy Head, a consultant to the Confederated Tribes of the Grand Ronde,
which includes the Clackamas.

He said the meteorite called ``Tomanoas'' by the Indians embodies three
heavenly realms - sky, earth and water. Clackamas youths were sent on
vigils to the meteorite to await messages from the spirit world and other
tribes also made pilgrimages, said Heavy Head, a Blackfoot.

The Grand Ronde submitted a claim for the meteorite to the museum last
September, under the Native American Graves Protection and Repatriation
Act. The federal law gives the museum until Feb. 29 to respond.

Ann Canty, a museum spokeswoman, would not comment on the claim. But she
and an architect of the new building made clear that it would not be easy to
move the meteorite from the planetarium, officially the Rose Center for
Earth and Space.

``Because the meteorite is so massive, parts of the facility had to
essentially be built around it,'' Canty said.

The meteorite had sat in the old planetarium since 1935 and was moved
with a large crane when that building was dismantled in 1997. Two years
before the new center was finished, contractors installed three structural
piles - 60-foot tubes driven into the ground - just to support it.

When tribal representatives visited in September, they ``had quite a
problem getting in to see the meteorite,'' Heavy Head said in a telephone
interview from his home in Salem, Ore.

Over six days, he and his wife Adrienne took thousands of pictures
documenting objects in the museum for possible repatriation. He said the
museum staff was ``civil but not necessarily cooperative'' when he asked
to see the meteorite.

``We had to remind them that we had a federal grant behind us,'' he
said. ``Eventually they gave us hard hats and let us in, but when we started
taking pictures, they freaked.''

The meteorite changed hands several times before the museum acquired it
in 1906. A part-time miner named Ellis G. Hughes discovered it in 1902 on
land belonging to an iron company, moved it into his barn and began charging
a quarter for admission.

In 1905, a state Supreme Court returned the meteorite to the iron
company; it was then bought for $20,600 by a New York woman, Mrs. William
Dodge, who donated it to the museum.

Tim McKeown, who oversees Indian claims for the National Park Service,
said proof of ownership could decide the case of the meteorite or the two
parties could reach agreement.

But McKeown said if the case goes to a federal review committee or to
court, it may take time.

Heavy Head said he does not expect a harmonious exchange given the
effort and expense devoted to building the meteorite into the Rose Center.

``It was a good thing that it traveled to the museum,'' he said. ``Their
ownership was essential to its safety. But now it needs to come home.''

Copyright 2000, AP

============
(3) BETWEEN GLOBAL WARMING & ICE AGE WARNING: WE STILL DON'T UNDERSTAND 
    PERIODIC CLIMATE CHANGE

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

Columbia University
New York, New York

February 18, 2000

Scientist Refutes Notion of Recent Climate as "Uniquely Benign," Sees
Evidence of Approaching Ice Age Despite Global Warming

By Kurt Sternlof

Paleoclimatologists agree that during the 10,000 years since the end of
the last ice age -- a period known as the Holocene -- Earth has enjoyed a
relatively warm and stable climate. During this period human civilizations
blossomed into global dominance. The question now is whether another ice age
is on its way? And if so, when?

At an international symposium convened by the Lamont-Doherty Earth
Observatory last October, the consensus answer was, "Yes, but not for at
least another five thousand years." While that sounds like a simple
reprieve, the issue of what the geologic record of past climate can tell us
about the future remains both complicated and contentious.

In a paper drawn from that symposium and solicited by Science for its 11
February 2000 issue, Lamont-Doherty paleoclimatologist George Kukla
argues that a currently popular interpretation of Holocene climate as
uniquely benign is both mistaken and misleading. He contends that the weight
of evidence shows that neither has the Holocene been uniformly benign, nor
is it without precedent in the geologic past. And if there's nothing unique
about our current climate pattern, there's no reason to think glacial
history won't repeat itself.

In fact, the geologic record reveals that Earth has experienced an
ongoing cycle of ice ages dating back millions of years. Cold, glacial
periods affecting the polar to mid-latitudes persist for about 100,000
years, punctuated by briefer, warmer periods called interglacials. The
Holocene is just another interglacial that is more than half over, Kukla
said.

It turns out that this ongoing cycle of glaciation closely matches
cyclic variations in Earth's orbit around the sun, leading many researchers
to conclude that orbit drives glaciation. This correspondence between orbit
and climate is called the Milankovich cycle, after the scientist who
analyzed and popularized it in the 1920s.

"I feel we're on pretty solid ground in interpreting orbit around the
sun as the primary driving force behind ice-age glaciation. The relationship
is just too clear and consistent to allow reasonable doubt," Kukla said.
"It's either that, or climate drives orbit, and that just doesn't make
sense."

Although the actual mechanisms that initiate and drive glaciation remain
a mystery, evidence suggests that the pendulum-swing to an ice age-type
climate may already be underway, Kukla said. For one thing, the
configuration of the sun and Earth is fast approaching what it was 116,000
years ago when the last interglacial period ended. And, while the annual
mean temperature on earth is now rising -- along with concerns that humanity
is to blame -- polar mean temperatures remain steady and ice fields in the
upper elevations of Greenland are actually expanding.

Three primary lines of geologic evidence are used to reconstruct Earth's
climate history during the last interglacial -- called the Eemian -- and the
transition into the most recent ice age, a period running from about 128,000
to 106,000 years ago. These come from ocean sediments, lake sediments and
ice cores from the polar regions. All of them provide indirect measures of
relative conditions such as temperature and so are open to interpretation.

Evidence from oxygen isotopes recorded in the shells of tiny ocean
creatures called foraminifers, a primary component of ocean sediment, yields
a measure of the changing global volume of continental ice through time.
Similar oxygen isotope data from water molecules trapped in successive
layers of old ice yield a measure of actual polar temperatures when the ice
formed. Plant pollen deposited in northern European lake sediments provides
a record of the transition on land between temperate woodlands and the
sparse grasslands that dominate during cold periods.

The view of the Holocene as uniquely benign grew out of an interpretation of
a single ice core collected in Greenland by a European team in 1992. The
oxygen isotope data from that core showed the Holocene to have been
uniformly mild in comparison to the Eemian, which appeared to have witnessed
relatively severe temperature swings. Once published, this interpretation
spurred other researchers to look for and find evidence of Eemian climate
extremes, which point to the Holocene as something other than just another
interglacial.

To Kukla, it is a classic example of an interesting, but mistaken,
theory gaining validation as other researchers jump onboard and, not
surprisingly, uncover evidence of what they expect to find. In fact, the
data from the European ice core disagrees with that of another core
subsequently collected nearby, as well as the overwhelming weight of ocean
sediment data. These lines of evidence show the Holocene to be similar to
the early and mid Eemian, he said.

The real problem Kukla sees is that the misinterpretation of Holocene
climate as unprecedented could interfere with our ability to recognize
future climate trends in evidence from the past.

"There is a tendency these days to focus on whatever agrees with global
warming and the idea that we are living in an unusual climatic epoch," Kukla
said. "Certainly the earth as a whole is warming right now. But you have to
remember that the tropics and subtropics comprise about 50 percent of the
total surface area; so, conditions there dominate the average."

On the other hand, glaciation emanates from the polar regions, which
together comprise only 14 percent of Earth's surface. And the preponderance
of evidence suggests that ice ages begin building at the poles thousands of
years before their effects are felt elsewhere, he said. Thus, the important
indicator of impending glaciation may not be global mean temperature so much
as the temperature difference between the poles and the equator.
Theoretically, the larger the difference the stronger the probable flow of
water vapor from the tropics toward the poles, where it would fall as snow
to feed the growing ice fields.

The ultimate significance of human-induced global warming may therefore
depend more on how it affects water-vapor transport, than its influence on
average global temperature or any effect on the underlying glacial cycle,
Kukla said. It is conceivable that greenhouse warming could even hasten the
transition to glacial conditions by exacerbating the polar/equatorial
temperature difference and increasing the rate of water transport poleward.

Based on the record revealed in ocean and lake sediments, the most
likely scenario over the next few thousand years is for the volume of ice in
the polar regions to slowly grow, gradually dropping sea level and
increasing the polar/equatorial temperature differential. Except near the
poles, oceans and continents will remain relatively warm, although the
climate will become increasingly unstable. Ultimately, a surge of built-up
polar ice into the mid-latitude oceans will plunge the continents into
ice-age conditions.

"As near as we can tell, that is what has happened in the past," Kukla
said, "and there's no reason yet to think anything has changed."

============
(4) ASTEROID 2000 BF19 AND THE MEDIA

From Daniel Fischer <dfischer@astro.uni-bonn.de>

Hi Benny,

you mentioned that you were "working on a review of the 2000 BF19
event and how it unfolded [...] to focus on [...] also how the
science media reacted to the story." (CCNet of Feb. 14)

Well, being part of the latter with, among other (printed) outlets,
http://www.astro.uni-bonn.de/~dfischer/mirror.html - The Cosmic Mirror,
here is how the story unfolded for me. I happened get online in that
short interval between the announcement of the possibility of an impact
and after Milani had found the new data and removed the asteroid from
his "Risk Page" (http://newton.dm.unipi.it/neodys/risk.html) - but
before the announcement about the 'all clear' had been posted widely.

Since the asteroid was no longer linked on the Risk Page, I checked its
homepage
(http://newton.dm.unipi.it/cgi-bin/neodys/neoibo?objects:2000BF19;main)
and found no dangerously close approaches either - thus I posted only a
small notice in http://www.astro.uni-bonn.de/~dfischer/mirror/173.html
(where the links to the respective CCNet issues and news media stories
were added later): "Another minimally hazardous asteroid come - and gone."

Lessons learned here: a) while many science writers read the CCNet
nowadays and get the news about possible impactors first-hand, it seems that
only when it's in the New York Times, it's making news basically everywhere.
Amazing that this "if it's in the NYT, it must be important" attitude from
the old pre-internet days still prevails today.

b) Once more most reports I've seen after the 'all clear' talked about
the astronomers "correcting" their wrong prediction, and hardly any
stressed that this time things went almost like in the textbook for
planetary defense (if there is such a thing :-): Possible impactor
spotted, call out for more data, data come in, all clear sounded, and
all that within hours.

And c) I would still consider it a good thing if there would be a link
on the NEODys Risk Page to risks that are history, just that one could
quickly check on previous cases and how they were resolved. It's all in the
CCNet archive, of course, but some info on NEODys would be helpful. I
actually talked about that with Milani at the Abano DPS Meeting last year,
and back then he promised to do just that some day.

Regards,

Daniel

P.S.: NEO news on the frontpage of Germany's largest-circulation tabloid
today! "BILD" has a recent NEAR picture of Eros on the frontpage (it was
http://near.jhuapl.edu/iod/20000217b), with the headline: "Photographed
for the first time: That's what an Earth Killer looks like." And in the
article (I've only read the part you can see without opening the vending
machine :-) it says about Eros that "it is being explored to be
destroyed."

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