PLEASE NOTE:


*

CCNet, 83/2000 -  5 September 2000
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(1) ASTEROID GIVES EARTH A COSMIC 'CLOSE SHAVE'
    THE TIMES, 5 September 2000

(2) UNIQUE METEORITE REPRESENTS NEW KIND OF COSMIC MATERIAL
    Michael Paine <mpaine@tpgi.com.au>

(3) GUYRA METEORITE PROBE TO START
    Michael Paine <mpaine@tpgi.com.au>

(4) INTRIGUING METEORITE DISCOVERED IN SASKATCHEWAN
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(5) "SPACE WEATHERING" CEMENTS ASTEROID-METEORITE LINK
    John Wagoner <stargate@astromax.com>

(6) RECENT CATACLYSMS ON THE SURFACE OF MARS?
    Ev Cochrane <ev.cochrane@ames.net>

===============
(1) ASTEROID GIVES EARTH A COSMIC 'CLOSE SHAVE'

From THE TIMES, 5 September 2000
http://www.the-times.co.uk/

BY MARK HENDERSON, SCIENCE CORRESPONDENT

Danger from outer space

THE Earth has had a cosmic near miss with an asteroid one third of a
mile wide, leading to new calls for an international task force to
devise ways of preventing a devastating impact.

The 2000 QW7 asteroid, which originated in the belt between Mars and
Jupiter, passed within 2.4 million miles of the Earth on Friday
morning, astronomers said yesterday. It was detected at Cornell
University's Arecibo Observatory in Puerto Rico, six days before it
hurtled past the Earth.

The asteroid was only twelve times further away than the moon when it
reached the nearest point to earth on its orbit - a close shave in
cosmic terms.

Lembit Opik, the Liberal Democrat MP who has campaigned for
international co-operation to counter the dangers of asteroids, said
that the Earth had had a very narrow escape. "It is as if someone had
thrown a marble at you across a tennis court and missed your head by
the width of your hand," he said. "It is all very well saying it
didn't hit us, but if it had been 2.4 million miles this way, which is
peanuts, we wouldn't be here talking about it today."

The near miss underlined the need for international co-operation to
share information on the extent of asteroid threats and to work out
means by which dangerous asteroids could be destroyed or diverted, he
said. Astronomers said that the discovery of 2000 QW7 was highly
significant as it offered an exceptional opportunity to study a
potentially hazardous asteroid (PHA) at close quarters.

"This is a very importat object," said Eleanor Helin, principal
investigator at Nasa's Near Earth Asteroid Tracking system (Neat), on
Maui, Hawaii. "It's so bright that astronomers can track it now and
through to the end of the year. It's a bit of a mystery why we haven't
seen this one before." Asteroids are classified as PHAs if they are
larger than a couple of hundred metres across, and have orbits within
4.65 million miles of the Earth.

Gravitational nudges by the Earth, Mars or Jupiter could alter their
orbits, and set them on a collision course with our planet. Any such
impact would be devastating to life on Earth, and could wipe out up to
a quarter of the human population. An asteroid seven miles wide that
hit the Yucatan peninsula 65 million years ago, in what is now
Mexico, is widely accepted to have caused the extinction of the
dinosaurs and three quarters of the other species living on the planet.

An asteroid about 60 metres across landed at Tunguska in Siberia in
1908, flattening trees for 13 miles and killing hundreds of reindeer.
Had the impact been in the centre of London, everything inside the M25
would have been destroyed. Scientists say that if an asteroid the size
of 2000 QW7 - which is nine times as large as the Tunguska asteroid -
were to hit the Earth, the devastation it would cause would be
frightening. If it landed in the Atlantic Ocean, everything within two
miles would be vapourised and the east coast of the United States and
the west coast of Europe would be swept by tidal waves. Molten debris
would continue to rain down for weeks after the impact, and dust
particles would cause effects similar to a nuclear winter".

Mr Opik said: "It would not be as bad as the dinosaurs, but you might
estimate that one in four of the world's population would die in the
end."

Both the British and US armed forces are believed to be studying ways
in which an asteroid could be blasted off course by nuclear attack.

Copyright 2000, Times Newspapers Ltd.

----------
MODERATOR'S NOTE: Can anyone please tell me what all the fuss is about
asteroid 2000 QW7? Three decades ago, detecting that an asteroid was
coming to 12 times the distance of the moon was unusual. But now it is
happening *all the time*, as CCNet readers can easily appreciate from
the chronological list of such objects provided by the Minor Planet
Center [http://cfa-www.harvard.edu/iau/lists/CloseApp.html].
 
The MPC list of such objects is particularly long for 2000 because
current discoveries are often rather near the earth when they are
found. Only tree months ago, for instance, an asteroids came to
*one-tenth* the distance of 2000 QW7 - two days *before* it was
discovered! Of course, that object, 2000 LG6, was very small - only a
few meters across and unable to do significant damage if it hit.
Nevertheless, I believe that increasing NEO search efforts will
ultimately result in a growing awareness that so-called 'close
approaches' by asteroids such as 2000 LG6 or 2000 QW7 are happing all
the time. In may ways, they constitute a general feature of our
immediate cosmic environment. As long as we fail to established
comprehensive detection and deflection systems, outer space will remain
as uncertain and chancy as Russian Roulette.
 
Benny J Peiser

===================
(2) UNIQUE METEORITE REPRESENTS NEW KIND OF COSMIC MATERIAL

From Michael Paine <mpaine@tpgi.com.au>

Dear Benny,

An article about a recent meteorite fall.

regards
Michael Paine

Chemists Find Primordial Meteorite In A Class By Itself
Science Daily Magazine
http://www.sciencedaily.com:80/releases/2000/09/000904093243.htm

WEST LAFAYETTE, Ind. - A chemical analysis of a rare, uncontaminated
4.5 billion-year-old meteorite that fell to Earth earlier this year
shows that its composition sets it apart from other meteorites found on
Earth, giving scientists a glimpse of the solar system that has not
been seen before.

The findings, when added to other studies of the meteorite, may provide
new information about the first moments of the solar system's
formation.

Purdue University chemist Michael Lipschutz, and his graduate student
Jon Friedrich, have analyzed 45 chemical elements in a meteorite that
fell to Earth into the wilds of northwestern Canada on January 18.

Chemically speaking, the meteorite, called the Tagish Lake meteorite,
falls into a classification called carbonaceous chondrite. The
carbonaceous chondrites are very rare and extremely interesting to
scientists. These meteorites contain carbon as organic compounds, some
of which are the basic building blocks for life, and interstellar
material, which comes from exploded stars outside of our solar system.

The Purdue study shows, however, that some compositional and
mineralogical features set the Tagish Lake sample apart from other
carbonaceous chondrites, placing it into a gap between two subtypes of
meteorites in that class.

"This meteorite is unique, and represents a new kind of planetary
material," says Lipschutz, a professor of chemistry who has studied
meteorites for more than 30 years. "From the chemical composition, it's
reasonable to assume it came from parts of the solar system different
than the ones that produced other carbonaceous chondrites previously
studied."

Lipschutz says the oxygen isotopes in the sample place the Tagish Lake
meteorite somewhere between the subtypes called CI and thermally
metamorphosed CM, putting the sample in a class by itself.

"Thermally metamorphosed meteorites came from parts of their parent
bodies that went through some type of major heating experience that
caused some volatile elements to vaporize," he says. "The fact that it's
not thermally metamorphosed means that this meteorite is much more
closely related to the CI meteorites than to any other kind of
meteorite."

CI meteorites are considered a "measuring stick" of sorts in
cosmochemistry, Lipschutz says, because they contain a chemical
composition similar to the outside surface of the Sun.

"The Tagish Lake meteorite is, in fact, a sample of the pre-solar
nebula, out of which the planets formed," he says. "We have never
before had a sample of this material."

Purdue is among four research centers worldwide that were selected to
perform laboratory analyses of the Tagish Lake meteorite. The studies
focused on trace elements - chemical elements found in parts per million
or parts per billion - which can be used to obtain information about the
meteorite's parent body and its history.

The findings, presented Thursday and Friday (8/31 - 9/1) at the
Meteoritical Society's annual meeting in Chicago, will be combined with
other studies of the meteorite to present a more complete picture of the
meteorite's history. While the possibilities have researchers very
excited, the meteorite's true significance remains to be fully
understood, Lipschutz says.

The studies at Purdue were completed using several analytical tools
including an inductively coupled plasma mass spectrometer, or ICPMS.
Friedrich, a doctoral candidate working with Lipschutz to chemically
analyze meteorites, adapted the ICPMS to study meteorite samples. The
ICPMS machine allowed him to complete his studies in a fraction of the
time required by standard methods.

The Tagish Lake meteorite fell to Earth in January in a remote area
between Atlin, British Columbia and Carcross, Yukon Territory. A week
later, nearby resident Jim Brook found the meteorite fragments while
driving home. He collected the samples using rubber gloves and kept them
frozen to prevent contamination or degradation.

The meteorite is considered one of the best preserved samples from our
early solar system, Lipschutz says.

Editor's Note: The original news release can be found at               
http://news.uns.purdue.edu/html4ever/0009.Lipschutz.yukon.html

c2000 Purdue University

===================
(3) GUYRA METEORITE PROBE TO START

From Michael Paine <mpaine@tpgi.com.au>

The following has just popped up on the ABC news site:
http://www.abc.net.au/news/newslink/daily/newsnat-5sep2000-35.htm

Guyra meteorite probe to start

Work is expected to start within days to find the Guyra meteorite.

The meteorite crashed into one of the shire's water supply dams in
November last year, attracting international attention.

While it is believed to be no bigger than a golf ball, it left a trail
a number of metres long and tunnelled itself four metres into mud.

Guyra's deputy mayor Robyn Jackson says Griffith-based company Ventura
Extraction will use a boat-based suction technique to bring the
meteorite to the surface.

Ho hum!!!
Mike

================
(4) INTRIGUING METEORITE DISCOVERED IN SASKATCHEWAN

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

University of Calgary
Calgary, Alberta

Press contact:
Andrew Wark
News Services & Media Relations
(403) 220-5727

July 27, 2000

Intriguing meteorite discovered in Saskatchewan

An odd-looking rock that a Saskatchewan farmer found in his field two
decades ago has been recently identified as a meteorite with significant
scientific value by researchers with the Prairie Meteorite Search.

Melvin Christensen of Kyle, Sask. found a strange seven-kilogram 'rock'
while cultivating land about 20 years ago. The heavy, black rock piqued
the interest of Andrew Bird, a third-year geology student at the
University of Calgary, who was hosting a Prairie Meteorite Search "show
and tell" on July 3 at the Kyle museum. Bird was examining rocks that
local residents thought could be meteorites.

"It was in the back of your mind that it just didn't look like a rock
that should be here," he says. "It was heavy with the black crust that
looked like it had been melted." Christensen put the strange rock in
the gazebo at his farmstead where it sat for two decades.

"The first thing that struck me was the perfect fusion crust and the
dished surface typical of meteorites, however, this meteorite had a
hole through it the size of a quarter," says Bird. "This is the first
stone I know of to have a hole." By chance, U of C planetary scientist
Alan Hildebrand, one of the project leaders of the Prairie Meteorite
Search, visited Bird later that day, and was puzzled by the unusual
surface on the dense and magnetic stone. Tests at the U of C showed
that the meteorite was 25 per cent nickel-bearing metal -- an
unambiguous indication of a rock from space.

Its extraterrestrial identity was then confirmed by John Wacker of the
Pacific Northwest Laboratory, located in Washington, who detected signs
of the meteorite's exposure to cosmic rays during its long journey in
space to Saskatchewan. The meteorite has a flattened pyramidal shape,
and is covered with hollows and a black fusion crust from surface melting
as friction slowed it in the upper atmosphere.

Cutting the meteorite revealed a very unusual texture of coarse fragments
mixed with a fine grained melted matrix. "This texture may represent a
mixture of melt and broken fragments produced by a large impact on the
meteorite's parent asteroid," says Hildebrand, a professor in the Department
of Geology and Geophysics. "This odd-ball texture will make the meteorite
an interesting study, and will provide one more clue about what the rest
of our solar system is like." This is the 13th new meteorite recovery in
Saskatchewan. Alberta is Canada's current leading province with 14
recoveries. The Prairie Meteorite Search locates meteorites by encouraging
prairie farmers to have rocks identified that they suspect to be
meteorites. The project consists of local publicity campaigns and
visits to towns with meteorite specimens to show local residents. The
project relies on people actually having seen meteorites and the
possibility of immediate identification to make discoveries.

"Farmers have been very responsive to the search and keenly interested in
meteorites," says Bird. "With their help we look forward to identifying
more this summer." About a dozen unconfirmed new meteorites are thought
to be in the hands of farming families across the prairies. The Prairie
Meteorite Search hopes to find four of them this summer. Anyone who
believes that they have meteorite is encouraged to bring it forward.

The Prairie Meteorite Search is a project of the Meteorites and Impacts
Advisory Committee to the Canadian Space Agency. This is Canada's
volunteer group charged with the investigation of fireballs and the
recovery of meteorites. Additional project funding comes from the
Canadian Society of Exploration Geophysicists, the Natural Sciences and
Engineering Research Council, and the University of Calgary.

The project leaders are Alan Hildebrand, University of Calgary; Peter
Brown, University of Western Ontario, and Martin Beech, University of
Regina.

For more details, see: www.geo.ucalgary.ca/PMSearch/ .

[NOTE: Images supporting this release are available at
http://www.geo.ucalgary.ca/PMSearch/PMSearch_kyle.htm]

====================
(5) "SPACE WEATHERING" CEMENTS ASTEROID-METEORITE LINK

From John Wagoner <stargate@astromax.com>

For decades planetary scientists have struggled to learn which
asteroids are the source of ordinary-chondrite meteorites, which make
up more than 80 percent of all known falls on Earth. The most likely
"parents" were thought to be the rocky bodies called S-types that
dominate the inner asteroid belt. But there's a compositional mismatch:
the S asteroids' slightly red color and weak spectral lines implied
that they contained too much metal to be the parent bodies for the
chondrites. Even Galileo's flybys of the S asteroids 243 Ida and
951 Gaspra failed to solve the mystery. So some researchers proposed
that some kind of "space weathering" was masking the asteroids' true
optical properties. Others posited the existence of an entire
population of undiscovered asteroids that were peppering Earth with
their chondritic castoffs.

The solution, it turns out, had unknowingly been discovered 25 years
ago. In 1975, while probing why the lunar regolith becomes darker and
redder with time, Bruce Hapke (now at the University of Pittsburgh)
and two colleagues proposed that the solar wind slowly evaporated the
lunar soil, causing individual grains to be coated with a microscopic
film of iron droplets just a few nanometers (billionths of a meter)
across. "Our suggestion was completely ignored at the time," recalls
Hapke, in part because no one could find any trace of the vapor
deposits.

But at this week's meeting of the Meteoritical Society, held in
Chicago, meteorite specialists at last convinced themselves that space
weathering really does happen, and that "nanophase iron" is primarily
responsible for it. "It's a pretty tight case," notes Carle Pieters
(Brown University). "Observations, experiments, and theory are now all
telling us the same thing." The stage for this consensus was set in
1993, when electron microscopy by NASA-Johnson Space Center
researchers Lindsay P. Keller and David S. McKay revealed the tiny
iron droplets in lunar samples from the Apollo 16 and 17 landing
sites. They theorized that the iron is deposited from the puff of
vapor created when micrometeorites slam into the lunar soil.

"I think everyone now agrees that ordinary chondrites come from the S
types," observes Beth Clark (Cornell University). She has found
evidence of space weathering in detailed spectra of the asteroid 433
Eros gathered by the NEAR-Shoemaker spacecraft. In Chicago Clark
reported that Psyche, the largest crater on Eros, exhibits patches of
soil that are much brighter and slightly redder than elsewhere. She
believes the bright patches were exposed by tiny landslides. Once a
fresh surface is exposed to space, suggests Clark Chapman (Southwest
Research Institute), the microscopic film of iron begins to
accumulate, first reddening then darkening over time.

Despite the newfound optimism, the case for space weathering won't be
considered ironclad until the tiny beads can be found in
ordinary-chondrite meteorites themselves. And that, Clark and Pieters
agree, may prove difficult even with state-of-the-art microscopic
techniques.

Copyright 2000 Sky Publishing Corporation.

=============================
* LETTERS TO THE MODERATOR *
=============================

(6) RECENT CATACLYSMS ON THE SURFACE OF MARS?

From Ev Cochrane <ev.cochrane@ames.net>

Thanks for this update, Benny. 

Scientists will continue to be baffled by new clues about Martian
meteorites and Martian geology for the simple reason that their
estimates of the age of the most recent Martian geological events are
off by several billion years. For many years now I have been claiming
that Mars was geologically active in the recent prehistoric past. I
have also written extensively on the impossibility of reconciling the
evidence from Martian meteorites with conventional astronomy.  No one
listens, of course, but with each passing month the evidence continues
to mount for recent cataclysmic episodes on the surface of Mars.

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