PLEASE NOTE:
*
CCNet 26/2002 - 19 February 2002
-------------------------------
"At the time of the Eltanin impact, Homo erectus was
emerging in
Africa, and beginning to spread into cooler Eurasia. It is
tempting
to speculate that an impact in the South Pacific could have been
a
stimulus for humanity's first great migration out of
Africa."
--Henry Gee, Nature 1997
"The phrase mass extinction often calls to mind such
potential
culprits as asteroid impacts and volcanism. But new research
suggests
that in the case of a die-off of marine creatures that occurred
two
million years ago, at the interface of the Pleistocene and
Pliocene
epochs, a different phenomenon was to blame. According to a
report appearing
in the February 25 issue of the journal Physical Review Letters,
cosmic
rays from the explosion of a nearby supernova may have done these
animals in."
--Scientific American, February 2002
"They are the most destructive events in the universe, vast
eruptions that rip apart stars and blast radiation across space.
But
supernovae may also play constructive roles in the cosmos -
recent
scientific research has revealed that these stellar annihilations
had a
crucial impact on human evolution."
--Robin McKie, The Observer, 17 February 2002
(1) STUDY SUGGESTS SUPERNOVA SNUFFED OUT MARINE LIFE TWO MILLION
YEARS AGO
Michael Paine <mpaine@tpgi.com.au>
(2) OCEANIC IMPACTS AND RELATED ENVIRONMENTAL PERTURBATIONS
A. R. Gersonde
(3) THE ELTANIAN OCEAN IMPACT 2 MILLION YEARS AGO
NATURE NEWS SERVICE
(4) HOW STAR BLASTS FORGED MANKIND: DID COSMIC DISASTER CHANGE
HOMINID
EVOLUTION?
The Observer, 17 February 2002
(5) COMETARY DUST LOADING DETECTED AROUND THE SUN
CNN, 18 February 2002
(6) NEWFOUND COMET IS BRIGHTENING
Astronomy.com, 16 February 2002
(7) WHEN CHIPS FOR BARTERING FALL FROM TEH SKY
The New York Times, 19 February 2002
(8) SEARCH AND OBSERVATIONS OF SAPCE DEBRIS AND NEAR EARTH
OBJECTS AT INASAN
L.V. Rykhlova et al.
(9) PREDICTION OF THE MOTION OF ASTEROIDS AND COMETS OVER LONG
INTERVALS OF
TIME
I. Wlodarczyk
(10) HYPERVELOCITY IMPACT CRATERING ON ICE
M.J. Burchell et al.
(11) RADAR CONSTRAINTS ON ASTEROID REGOLITH PROPERTIES
C. Magri et al.
(12) COLLISION-INDUCED THERMAL EVOLUTION OF A COMET NUCLEUS
R. Orosei
(13) A RAIN OF ORDINARY CHONDRITIC METEORITES IN THE EARLY
ORDOVICIAN
B. Schmitz et al.
(14) AND FINALLY: CAUGHING A SIGH OF RELIEF AS CAR EXHAUSTS 'MAY
SLOW GLOBAL
WARMING'
Ananova, 19 February 2002
================
(1) STUDY SUGGESTS SUPERNOVA SNUFFED OUT MARINE LIFE TWO MILLION
YEARS AGO
>From Michael Paine <mpaine@tpgi.com.au>
Dear Benny
See the Scientific American article below. Note that the Eltanin
ocean
impact, possibly by a 4km diameter asteroid, occurred 2.15Ma. Its
global
environmental consequences do not appear to have been studied in
detail
but simply the ejection of huge quantities of chlorine-laden
seawater in
to the atmosphere would have affected (if not wiped out) the
ozone
layer.
regards
Michael Paine
Study Suggests Supernova Snuffed out Marine Life Two Million
Years Ago
http://www.sciam.com/news/021302/1.html
The phrase mass extinction often calls to mind such potential
culprits as asteroid impacts and volcanism. But new research
suggests that in the case of a die-off of marine creatures that
occurred two million years ago, at the interface of the
Pleistocene and Pliocene epochs, a different phenomenon was
to blame. According to a report appearing in the February 25
issue of the journal Physical Review Letters, cosmic rays from
the explosion of a nearby supernova may have done these
animals in.
Conventional explanations for the extinction, which claimed the
lives of numerous molluscs, look to the emergence of the
Panama isthmus or climate cooling from Northern Hemisphere
glaciations. But analysis of a cluster of stars in our galactic
neighborhood known as the Scorpius-Centaurus association led
Narciso
Benítez of Johns Hopkins University and colleagues to conclude
otherwise.
They determined that Scorpius-Centaurus has produced 20
supernovae explosions-the swan songs of dying stars-during the
last 11
million years. One of these outbursts, the team proposes,
occurred around
two million years ago, and took place close enough to Earth
for its cosmic rays to catalyze large-scale destruction of the
ozone
layer. The resulting increase in harmful ultraviolet rays from
the sun reaching
Earth, they say, could have killed the marine plankton that
molluscs
depend on for food.
The supernova explosion hypothesis for mass extinctions has
floated
around in academic circles for more than four decades, but the
new
study seems to make the strongest case yet. The next step,
Benítez and his
co-authors note, will be to determine more precisely the time and
distance at which each supernova explosion took place. "A
coincidence in
time between the [supernova] expected to have the strongest
effects on the
biosphere and the Pleistocene-Pliocene extinction," they
write, "would
strongly support the existence of a link between both
events."
-Kate Wong
c2001 Scientific American
===============
(2) OCEANIC IMPACTS AND RELATED ENVIRONMENTAL PERTURBATIONS
R. Gersonde, Alfred
Wegener Institute, P.O. Box 120161, Bremerhaven 27515, Germany.
Catastrophic Events Conference, Vienna, 2000 3049.pdf
Only ca.13% of the ca.165 known terrestrial impact structures
have been
identified to originate in marine environments. The marine
impacts have been
reported from shallow water marginal or epicontinental seas,
except one, the
Eltanin impact, that was discovered in the deep-sea basin of
the southeast Pacific. Reasons for the mismatch between the
numbers of
continental and deep-sea impacts include (i) the relatively young
age of
oceanic basins, (ii) the post-impact burial of marine impact
structures,
(iii) the deceleration and disintegration of small projectiles in
the
water column preventing the formation of impact traces at the
deep-sea
floor, (iv) the inaccessibilty of the deep-sea floor, and (v) the
lack of
programs for the detection of oceanic impacts. In contrast to
continental
impacts, oceanic impacts will generate megatsunamis that could
potentially
devastate coastlines. This includes destruction of coral reefs,
destabilisation of shelf ice and shelf deposits and the backwash
of
terrestrial material. Future oceanic
impacts represent a potential hazard because impact-generated
large-scale
tsunamis can cause enormous loss in populated coastal areas,
including areas
located at great distances of the impact ground-zero. Another
specific
threat related to oceanic impacts is the ejection of large
quantities of water and salt into the atmosphere. Such deposition
might lead
to depletion of the ozone shield, to acidification of surface
regions and
could affect the Earth´s albedo and the power of greenhouse
forcing. Despite
the great potential of oceanic impacts for causing sudden
disturbance of past and future Earth´s climate, environment and
life, our
knowledge on these processes is still quite limited. To date, the
only
example for a deep-ocean impact is the late Pliocene (2.15 Ma)
Eltanin
impact in the 5000 m deep Bellingshausen Sea. Originally
discovered in 1981,
based on an Ir-anomaly[1], and documented in more detail in 1997
[2], the
Eltanin impact represents a baseline for further impact-related
studies and
modeling, and the identification of other deep-sea impacts.
Combined with
seismic and sediment core data, numeric modeling
represents the most important tool to understand the complex
impact-related
processes such as short-term effects (pressure, velocities, shock
waves) in
the water column, large scale oceanic phenomena (e.g. tsunami
generation and
propagation), the effects of shock waves and oceanic processes on
the
sediment cover and basement, as well as perturbations in
atmospheric and
environment.
References: [1] Kyte, F.T. et al. (1981) Nature, 292, 417-420.
[2]
Gersonde, R. et al. (1997) Nature, 390, 357-363.
Catastrophic Events Conference 3049.pdf
=============
(3) THE ELTANIAN OCEAN IMPACT 2 MILLION YEARS AGO
>From NATURE NEWS SERVICE
http://www-geology.ucdavis.edu/~GEL3/Plioceneimpact.html
Ocean splashdown
by Henry Gee
An asteroid between one and four km in diameter that splashed
into the
Southern Ocean, 1500 km SW of Chile, just over two million years
ago, may
have worsened a period of global cooling that saw the emergence
of modern
humans. The asteroid impact explains several other puzzles, too,
as Rainer
Gersonde of the Alfred Wegener Institute for Polar and Marine
Research in
Bremerhaven and colleagues discuss in the 27 November 1997
Nature.
The impact in question was first discovered during a cruise of
the Eltanin
in the 1960s: betrayed by anomalously high amounts of iridium in
ocean-bed
cores. The Eltanin impact is the only example of the 140 known on
Earth to
have occurred in the deep ocean. Given that 70% of the Earth's
surface is
underwater, and most of that is ocean, we would expect most
incoming
asteroids and comets to meet watery graves. Statistics suggests
that around
500 bodies the size of the Eltanin asteroid hit the oceans in the
past 540
m.y.: almost one every million years, on average. This is why the
Eltanin
impact site is so valuable, and why Gersonde and his colleagues
have taken
another look, their results coming from a cruise in 1995 by the
research
ship Polarstern.
The impact left a distinctive 'signature' of geological layers,
very like
that of the Chicxulub impact. Lowest in the 'impact' sequence is
a thick
layer of disordered rubble, full of chunks of rock up to 50 cm
across: this
layer represents the large-scale disturbance immediately after
the impact as
the ten-megaton blast ripped up the ocean floor. This layer took
around four
hours to settle after the blast. Smaller particles, such as
grains of sand,
took longer to settle, explaining why this layer was found
immediately above
the rubble layer.
Capping the whole sequence is a thin layer of very fine sediment,
dispersed
over a wide area. This would have contained fine-grained material
(including
vaporized asteroid) flung high into the air and which took days
or months to
settle out. This layer contained the iridium.
The Eltanin asteroid was much smaller, less than half the
diameter of the
asteroid of the Chicxulub impact. There is no trace of a
submarine Eltanin
crater; indeed, most of the asteroid probably vaporized before it
could
leave much of a scar on the ocean floor. Nevertheless, Eltanin
was still an
impact to be reckoned with, being just large enough to disturb
the global
ecosystem. The impact would have blasted sediment high into the
atmosphere,
explaining why fossils of microscopic deep-sea diatoms made their
way to the
mountainous interior of Antarctica. It would also have sent
terrifyingly
high tsunamis to broach on coasts all over the South Pacific and
Southern
Oceans. These would have washed hundreds of metres inland,
explaining the
strange jumble of terrestrial and marine animals from
contemporary deposits
in Peru.
The impact would also have sent enormous quantities of water and
dust into
the atmosphere, which would have influenced the climate. Although
polar
ice-sheets had become well-established by that time, the Earth
was yet to
settle into the pronounced cycle of continental glaciation that
has
characterized the past 1-2 million years.
At the time of the Eltanin impact, Homo erectus was emerging in
Africa, and
beginning to spread into cooler Eurasia. It is tempting to
speculate that an
impact in the South Pacific could have been a stimulus for
humanity's first
great migration out of Africa.
©Macmillan Magazines Ltd 1997 - NATURE NEWS SERVICE
=============
(4) HOW STAR BLASTS FORGED MANKIND: DID COSMIC DISASTER CHANGE
HOMINID
EVOLUTION?
>From The Observer, 17 February 2002
http://www.observer.co.uk/uk_news/story/0,6903,651829,00.html
Cosmic radiation two million years ago had a crucial impact on
our evolution
Robin McKie
They are the most destructive events in the universe, vast
eruptions that
rip apart stars and blast radiation across space.
But supernovae may also play constructive roles in the cosmos -
recent
scientific research has revealed that these stellar annihilations
had a
crucial impact on human evolution.
Two million years ago, just as the Earth's primitive apemen were
evolving
into big-brained humans, a pair of supernovae explosions occurred
near
Earth.
Our planet was buffeted with blasts of radiation - with
devastating effects.
'These supernovae would have blown away our protective ozone
layer,' said Dr
Narciso Benítez, of Johns Hopkins University, Baltimore.
'Earth lost its protection against ultraviolet solar rays and for
several
hundred years the planet would have been battered by intense
radiation. All
sorts of mutational damage to animals' DNA would have occurred.
New species
could have emerged as a result. It is possible Homo sapiens may
have been
one of these.'
A supernova occurs when a hot, dense star burns up its fuel too
quickly and
suddenly implodes, generating shock waves and intense blasts of
radiation
across space. When a supernova explodes, it outshines all the
other 200
billion stars that make up our galaxy, the Milky Way.
The likely impact of a supernova's radiation led scientists in
the past to
speculate that one may have affected evolution on Earth. But
calculations
indicated that fields of interstellar gas would have dissipated a
supernova's radiation and blunted its impact.
However, Benítez and his colleague, Dr Jesús Maíz-Apellániz,
of the Space
Telescope Science Institute in Baltimore, now believe that at
least two
supernovae occurred near Earth two million years ago. The first
would have
blasted space free of interstellar particles; the second would
have struck
Earth at full force, destroying its ozone layer.
'Supernovae are very rare. So two such explosions occurring
relatively close
together might seem unlikely. However, we have discovered that
around this
time a group of hot, dense young stars - just the type that turn
supernova -
passed relatively close to Earth,' said Maíz-Apellániz.
'Some of this group - known as the Sco-Cen group - would have got
within 100
light years of us, which, astronomically, is not a great
distance. Our
calculations suggest that two or three of these exploded as
supernovae.'
In short, Earth was hit by an astronomical double whammy - though
the
discovery that supernova-prone stars passed near Earth two
million years ago
does not, on its own, provide complete proof, as the two
scientists admit.
However, further support for the theory, to be published in
Physical Review
Letters next week, has been found by scientists studying samples
of
sediments from the Pacific ocean floor. German researchers
recently
uncovered an isotope of iron known as iron-60 in ocean bed
samples laid down
about two million years ago. 'Iron-60 is made by only one thing
in nature -
a supernova,' said Benitez. 'A supernova sprays space with many
different
elements. Many are rare - like iron-60. These particles hit our
atmosphere
and settle like a thin layer of dust over the planet.'
Intriguingly, the iron-60 layer found by the German group did not
come from
a single supernova but appeared to come from a number of them.
'Different
layers seem to have fallen at different times, but all around two
million
years ago,' said Benítez.
In addition, observations of space around our Sun have revealed
that unlike
the rest of the galaxy, space near us has little interstellar gas
in it.
'Essentially it is missing much of its dust and gas - just as if
a supernova
had cleaned it out,' added Maíz-Apellániz.
In other words, our tiny corner of the galaxy appears to have
been swept
clean by a supernova brush about two million years ago.
Intriguingly, at
just this time, a set of extinctions - known as the
Pliocene/Pleistocene
extinctions - is also known to have occurred.
Geologists have found that plankton and molluscs were wiped out
in vast
numbers and that land animals and plants were also affected. 'We
now think
these creatures were killed off because Earth's ozone was blasted
away by
two or more supernovae,' said Benítez.
'There would have been no protection against the Sun's intense
ultraviolet
radiation. All sorts of changes could have resulted.'
It was also around this time that mankind's direct ancestor, Homo
erectus,
the species considered to be the first true human being, appeared
in Africa
and Asia after replacing more primitive ape-like creatures such
as
Australopithecus africanus. These beings may have been some of
the lucky few
who were able to advantage of conditions in these hazardous,
radioactive
times. This triumph only occurred thanks to this celestial
intervention,
however.
'It is a very interesting idea,' said Professor Chris Stringer,
of the
Natural History Museum in London. 'Certainly, quite a number of
extinctions
around this period. At the same time, Homo erectus was beginning
to make its
way in the world.
'However, we would have to tie down the datings of the supernovae
eruptions
and also the dates that the layers of the iron-60 were deposited
before we
could start to take such an idea seriously as a cause of the
changes we see
in the fossil records'.
Copyright 2002, The Observer
MODEARTOR'S NOTE: On cosmic impacts as agents of punctuated human
evolution,
see: Reinventing Darwin Again: How Asteroids Impacted Human
Evolution
http://www.space.com/searchforlife/human_evolution_010424-1.html
=======
(5) COMETARY DUST LOADING DETECTED AROUND THE SUN
>From CNN, 18 February 2002
http://www.cnn.com/2002/TECH/space/02/18/sun.ring/index.html
Sun ring could point the way to distant planet systems
By Richard Stenger
(CNN) -- A newly detected disk around the sun could narrow down
the search
of other star systems that might harbor planets, according to
scientists.
Astronomers with the European Space Agency said this month that
they had
found the first direct evidence of the bright dust ring, located
beyond the
orbit of Saturn.
Young stars are known to posses thick bands of dust, gas and
debris. In the
inner regions, planets can coalesce. Farther out, the more thinly
distributed material can clump into sparse bands of miniature ice
objects.
Any dusty leftovers disappear into deep space. But if an older
star such as
the sun possesses a dusty ring, some hidden source of material
must be
sustaining it, the agency's researchers say.
Replenishing the one around the sun requires 50 tons of dust each
second,
estimated agency scientist Markus Landgraf.
His colleague Malcolm Fridlund elaborated.
"The dust has to come from somewhere," Fridlund said.
"The only explanation
is that the star has planets, comets, asteroids or other bodies
that collide
and generate the dust."
The dust ring is fed by the constant collisions of primordial
comets in the
outer reaches of the solar system, the so-called Kuiper Belt
Objects,
according to the researchers.
Viewed from afar, the sun's ring likely would resemble a disk
such as this
one around a star called HR 4796A.
The finding could give a major boost to the search for planets
around other
stars in the galaxy.
"If we see a similar dust ring around a mature star like the
sun, we'll know
it must have asteroids or comets," Landgraf said. "If
we see gaps in the
dust ring, it will probably have planets that are sweeping away
the dust as
they orbit."
Satellites such as the Cosmic Background Explorer and Ulysses
helped
astronomers find the disk around the sun. Future planet-seeking
missions
such as the space agency's Eddington and Darwin may help refine
the search
around other stars in the coming decades.
Based on data from satellites and observatories, promising places
to
investigate include the Vega and Epsilon Eridani star systems,
researchers
say.
Copyright 2002, CNN
==========
(6) NEWFOUND COMET IS BRIGHTENING
>From Astronomy.com, 16 February 2002
http://www.astronomy.com/Content/Dynamic/Articles/000/000/000/763khkce.asp
A newly discovered comet could become naked-eye this spring.
by Vanessa Thomas
While Southern Hemisphere observers have been treated to a
dazzling Comet
LINEAR lately, a new comet has shown up in Northern Hemisphere
skies and may
put on nearly as nice of a show this spring.
During the last few days of January, comet watchers north of the
equator
wished they could transport themselves southward as Comet 2000
WM1 (LINEAR),
at the time only visible from the Southern Hemisphere, flared to
better than
3rd magnitude. Just a couple days later, though, two comet
hunters found a
new fuzzy object in the western sky that soon eased the pain of
northern
observers unable to see Comet LINEAR's grand display.
On February 1 two comet hunters, Kaoru Ikeya of Japan and Daqing
Zhang of
China, independently reported spotting an unidentified comet in
their
evening skies. Using a 25-centimeter (10-inch) telescope,
Ikeya (who has
discovered or co-discovered several comets before), estimated
that this new
visitor was about 9th magnitude. Zhang, who used a 20-centimeter
(8-inch)
reflector, estimated that it was slightly better at magnitude
8.5.
Soon, other amateur astronomers, from both hemispheres, reported
seeing the
comet as well. Over the past two weeks, they've watched as Comet
2002 C1
(Ikeya-Zhang) has brightened to better than magnitude 7.5.
Additionally,
some observers report that a thin tail has already begun to
develop.
Early estimates of the comet's orbit has it reaching perihelion
on March 8.
Astronomers currently predict that its peak brightness could hit
magnitude 4
several days later. Unfortunately, Comet Ikeya-Zhang will still
be quite
close to the sun at that time. But it has the potential to remain
a
naked-eye object through April. Comet watchers know their
favorite targets
can be unpredictable and will keep a close watch on Comet
Ikeya-Zhang in
case it has some surprises in store.
Currently in Cetus and moving northward, Comet Ikeya-Zhang will
make its
closest approach to the sun while in Pisces before moving into
Pegasus in
late March. To view star charts showing the comet's position over
the next
two weeks, click on the "related stories" below.
Copyright © 1996-2002 Kalmbach Publishing Co.
============
(7) WHEN CHIPS FOR BARTERING FALL FROM TEH SKY
>From The New York Times, 19 February 2002
http://www.nytimes.com/2002/02/19/science/space/19METE.html
By KENNETH CHANG
Want a piece of a historic meteorite from the Smithsonian
collection or
maybe the Natural History Museum in London?
Offer a blank check and the answer will be, sorry, it is not for
sale.
But there is a good chance that the curators at those and other
natural
history museums will give it to you - if you can trade another
extraterrestrial rock they want.
Rare meteorites act as their own currency, giving private
collectors access
to collections at the most prestigious museums.
That is how two pieces of the Willamette Meteorite - the prized,
15 1/2-ton
centerpiece of American Museum of Natural History's planetarium -
wound up
at auction this month, to the dismay of Oregon Indians who regard
it as
sacred and to the concern of some museum association officials.
In recent years, an avid collector's market has pushed prices for
precious
meteorites to thousands of dollars an ounce, often too expensive
for
universities and museums. What academic institutions do have are
historic
meteorites that collectors want a piece of. Hence, they trade.
"We're forced into doing that kind of thing," said Dr.
Rhian H. Jones,
curator at the University of New Mexico's Institute of
Meteoritics. "The
private dealers, they're not donating the material to research.
If we want
to do the research, we have to get the material into the
collection. It
doesn't harm our collection significantly to trade a small piece
of
meteorite that we have a large amount of it for something that
has
scientific value."
Once in private hands, a museum meteorite is typically cut into
smaller and
smaller pieces and sold and resold at sometimes considerable
profit. Or the
collector makes more trades to gain yet more rocks.
Collectors say the high values have spurred more people to hunt
for
meteorites, and that aids the scientists.
"If it were not for the new meteorite bonanza of the 90's,
the research
community would never have had so many new rare and exciting
specimens made
available to them," said Michael I. Casper, a meteorite
dealer and collector
in Ithaca, N.Y.
But for museum visitors, sometimes there is slightly less to see.
At the top
of the Willamette Meteorite - the largest ever found in the
United States -
is a smooth, polished surface about a foot wide where the museum
cut off a
28-pound chunk about four years ago. Small fragments from that
chunk are now
for sale at mhmeteorites.com. The Web site informs the viewer:
"Available
exclusively at Mile High Meteorites."
The museum had traded the 28- pound chunk to a private collector,
Darryl
Pitt of New York City, for a small piece of a meteorite from
Mars, and Mr.
Pitt, in turn, cut a 3.4- ounce slice off his chunk, which he
auctioned off
on Feb. 10 for $11,000.
The buyer, Matt Morgan, owner of Mile High Meteorites, will cut
it into six
or seven pieces, keeping some, selling others. A second, smaller
piece of
the meteorite, which Mr. Pitt had obtained in a trade with the
Natural
History Museum in London, sold for $3,300.
The auctions have upset descendants of the Clackamas Indians in
Oregon,
where the meteorite was found. They regard it as a spiritual
union of earth,
sky and water. The trade between Mr. Pitt and the museum occurred
a couple
of years before the claim; the museum says it will not cut any
more pieces.
The buyer of the smaller piece, Dr. David Wheeler, a chiropractor
in West
Linn, Ore., has said he may donate it to the Confederated Tribes
of Grande
Ronde, which includes the Clackamas. Mr. Morgan said Friday that
he and his
two fellow investors would also give a small piece to the tribes.
But even had there been no cultural considerations, some find it
troubling
that a piece of a meteorite was cut off not to be studied, but to
fill the
desire of a collector.
"It's almost defacing," Nancy Heller of New York City,
a visitor to the
planetarium last week, said of the Willamette Meteorite. "I
can't imagine
anyone deliberately wanting to damage a work of art. This is not
exactly a
work of art, but it is a museum."
Dr. Geoffrey Lewis, chairman of the ethics committee of the
International
Council of Museums, said that he was troubled by some of what he
had heard
about the meteorite trades and that his committee would review
the practice
when it met this summer in Paris. "Clearly, there are many
issues there,
which should be examined," he said.
He said he could not comment on the Willamette Meteorite trades
because he
did not know the details. But he cited several sections in the
council's
Code of Professional Ethics, which state that there should be a
"strong
presumption" against getting rid of specimens, that museum
professionals
should not participate in the buying or selling of objects for
profit, even
indirectly, and that collections should not be treated as
"realizable
assets."
Dr. Michael J. Novacek, the provost of science at the American
Museum of
Natural History, said tmuseumis not a member of the international
council
and that the museum's practices were entirely in line with the
code of
ethics established by the American Association of Museums, which
states that
sales or trades should occur "solely for the advancement of
the museum's
mission."
The trade with Mr. Pitt brought the museum a sample of a very
rare Martian
meteorite, more important scientifically than the fairly common
iron of the
Willamette Meteorite.
"Our motive is to raise the scientific value of the
collection," Dr. Novacek
said. "We don't view ourselves as out of compliance with any
ethics."
Still, when meteorite collectors view museum collections, they
sometimes
seem more like shoppers than visitors.
Mr. Morgan of Mile High Meteorites said he regularly traded with
museums at
a couple of universities. When he gets something new, he sends
e-mail
messages to the curators: "I say, are you guys interested in
any of this?"
He keeps catalogs of the museums' collections, so if they're
interested, he
can suggest what he would like in return.
Copyright 2002 The New York Times Company
============
(8) SEARCH AND OBSERVATIONS OF SAPCE DEBRIS AND NEAR EARTH
OBJECTS AT INASAN
Rykhlova LV, Bagrov AV, Barabanov SI, Kasimenko TV, Mikisha AM,
Smirnov MA:
Search and observations of Space Debris and near Earth objects at
INASAN
SPACE DEBRIS. ADVANCES IN SPACE RESEARCH 28 (9): 1301-1307
2001
The concept of Space Debris is tightly connected with the rapidly
developing
activity of men in space, and accompanied by a contamination of
the
surrounding space by artificial debris. Besides artificial
debris, in the
vicinity of the Earth is moving a large number of natural
celestial bodies:
comets, mini-comets, asteroids, meteor streams with fragments of
various
sizes and chemical composition. Our activity in the observations
concentrates in three directions: position observations of
artificial
objects on the geostationary orbit (GEO); photometric
observations on GEO
and LEO (low orbits); observations of natural near-Earth objects
(NEO).
Scientific investigations are carried out in the following
directions:
explosions of upper stages of rockets in LEO and GEO; solar
radiation
pressure and its influence on the evolution of orbits; space
debris on GEO;
natural objects' population in near-Earth space. (C) 2001 COSPAR.
Published
by Elsevier Science Ltd. All rights reserved.
Addresses:
Rykhlova LV, Russian Acad Sci, Inst Astron, Pyatnitskaya St 48,
Moscow
109017, Russia
Russian Acad Sci, Inst Astron, Moscow 109017, Russia
Copyright © 2002 Institute for Scientific Information
============
(9) PREDICTION OF THE MOTION OF ASTEROIDS AND COMETS OVER LONG
INTERVALS OF
TIME
Wlodarczyk I: Prediction of the motion of asteroids and comets
over long
intervals of time
ACTA ASTRONOMICA 51 (4): 357-376 2001
Difference of the mean anomalies of two starting orbits of a
minor planet or
a comet which only differ by an error of calculating of one of
the orbital
elements grows rapidly with time. This means that it is almost
impossible to
predict behavior of minor planets or comets on the orbit outside
the period
of time called the time of stability in our work. The time of
stability for
some selected minor planets and comets are given. For some minor
planets and
comets the time of stability is surprisingly short, about several
hundreds
years only.
Addresses:
Wlodarczyk I, WPKIW, Astronom Observ Chorzow Planetarium,
PL-41501 Chorzow,
Poland
WPKIW, Astronom Observ Chorzow Planetarium, PL-41501 Chorzow,
Poland
Copyright © 2002 Institute for Scientific Information
=========
(10) HYPERVELOCITY IMPACT CRATERING ON ICE
Burchell MJ, Grey IDS, Shrine NRG: Laboratory investigations of
hypervelocity impact cratering in ice ADVANCES IN SPACE RESEARCH
28 (10):
1521-1526 2001
Hypervelocity impact experiments on water ice targets have been
performed
using a two stage light gas gun. The resulting craters were
measured to
obtain the crater depth and diameter. From the data set for 23
impact
craters, damage equations have been obtained which give the
crater depth
(diameter) in terms of the dependence on impact velocity,
projectile
diameter and projectile density. The resulting damage equations
are compared
to those for another brittle material, glass. Scaling of the
excavated
crater volume with energy is shown to obey a simple power law
over 10 orders
of magnitude in energy (10(-7) to 10(3) J). (C) 2001 COSPAR.
Published by
Elsevier Science Ltd. All rights reserved.
Addresses:
Burchell MJ, Univ Kent, Unit Space Sci & Astrophys,
Canterbury CT2 7NR,
Kent, England
Univ Kent, Unit Space Sci & Astrophys, Canterbury CT2 7NR,
Kent, England
Copyright © 2002 Institute for Scientific Information
===========
(11) RADAR CONSTRAINTS ON ASTEROID REGOLITH PROPERTIES
Magri C, Consolmagno GJ, Ostro SJ, Benner LAM, Beeney BR: Radar
constraints
on asteroid regolith properties using 433 Eros as ground truth
METEORITICS & PLANETARY SCIENCE 36 (12): 1697-1709 DEC 2001
Radar data enable us to estimate an asteroid's near-surface bulk
density,
thus providing a joint constraint on near-surface porosity and
solid
density. We investigate two different approaches to simplifying
this joint
constraint: estimating solid densities by assuming uniform
porosities for
all asteroids; and estimating porosities by assuming uniform
mineralogy
within each taxonomic class. Methods used to estimate asteroids'
near-surface solid densities from radar data have not previously
been
calibrated via independent estimates. Recent spacecraft results
on the
chondritic nature of 433 Eros now permit such a check, and also
support
porosity estimation for S-class objects. We use radar albedos and
polarization ratios estimated for 36 main-belt asteroids and nine
near-Earth
asteroids to estimate near-surface solid densities using two
methods, one of
which is similar to the uncalibrated algorithms used in previous
studies,
the other of which treats Eros as a calibrator. We also derive
porosities
for the same sample by assigning solid densities for each
taxonomic class in
advance. Density-estimation results obtained for Eros itself are
consistent
with the uncalibrated method being valid in the mean; those
derived for the
full sample imply that uncalibrated solid densities are, at most,
a few tens
of percent too large on average. However, some derived densities
are
extremely low, whereas most porosity estimates are physically
plausible. We
discuss the relative merits of these two approaches.
Addresses:
Magri C, Univ Maine, 173 High St,Preble Hall, Farmington, ME
04938 USA
Univ Maine, Farmington, ME 04938 USA
Univ Arizona, Steward Observ, Vatican Observ Res Grp, Tucson, AZ
85721 USA
CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA
Copyright © 2002 Institute for Scientific Information
==========
(12) COLLISION-INDUCED THERMAL EVOLUTION OF A COMET NUCLEUS
Orosei R, Coradini A, De Sanctis MC, Federico C:
Collision-induced thermal
evolution of a comet nucleus in the Edgeworth-Kuiper Belt
ADVANCES IN SPACE RESEARCH 28 (10): 1563-1569 2001
In this work, we attempt an order-of-magnitude estimate of the
effects of
heating caused by low-velocity collisions on the structure and
composition
of an Edgeworth-Kuiper Belt object. This was done by using a
numerical code
developed for the study of comet nuclei. This code solves the
heat
conduction and gas diffusion equations in one dimension, within a
spherically simmetric porous body made of a mixture of ices and
dust. Ices
can sublimate, gas can flow within the porous matrix, and dust
can be
ejected by the gas flow escaping from the object. The code was
adapted to
the EKO case by adding the heat released by an impact in the
interior of the
body. Within the uncertainties in the values of parameters
describing the
EKO structure and the heat release due to impacts, it was found
that the
outcome of even a large collision cannot be taken for granted: in
some
cases, the impacted body is altered to depths of more than 1 km,
while in
some other cases very small effects are produced. The results
also point to
the interesting possibility of heat buildup within an EKO due to
multiple
impacts. (C) 2001 COSPAR. Published by Elsevier Science Ltd. All
rights
reserved.
Addresses:
Orosei R, CNR, Ist Astrofis Spaziale, Via Fosso Cavaliere 100,
I-00133 Rome,
Italy
CNR, Ist Astrofis Spaziale, I-00133 Rome, Italy
Univ Perugia, Dipartimento Sci Terra, I-06100 Perugia, Italy
Copyright © 2002 Institute for Scientific Information
===========
(13) A RAIN OF ORDINARY CHONDRITIC METEORITES IN THE EARLY
ORDOVICIAN
Schmitz B, Tassinari M, Peucker-Ehrenbrink B: A rain of ordinary
chondritic
meteorites in the early Ordovician
EARTH AND PLANETARY SCIENCE LETTERS 194 (1-2): 1-15 DEC 30 2001
Forty fossil meteorites with a total original mass of similar
to7.7 kg have
been recovered in the first systematic search for fossil
meteorites, pursued
in an active quarry in Lower Ordovician (480 Ma) marine limestone
in
southern Sweden. The meteorites represent at least 12 different
falls over a
seafloor area of similar to6000 m(2) during less than or equal
to1.75 Myr,
making the quarry one of the most meteorite dense areas known in
the world.
Geochemical analyses of relict chromite grains indicate that all
or most of
the meteorites are ordinary chondrites and probably L chondrites.
Mechanisms
for meteorite delivery from the asteroid belt to Earth were the
same 480 Ma
as today, however, the flux was one to two orders of magnitude
higher, most
likely reflecting the disruption of the L chondrite parent body
at about
that time. This is a major event in late solar-system history,
which may
also have led to an enhanced flux of asteroids to Earth during
similar to 30
Myr. (C) 2001 Elsevier Science B.V. All rights reserved.
Addresses:
Schmitz B, Ctr Earth Sci, POB 460, SE-40530 Gothenburg, Sweden
Ctr Earth Sci, SE-40530 Gothenburg, Sweden
Vaner Museum, SE-53117 Linkoping, Sweden
Woods Hole Oceanog Inst, Dept Marine Chem & Geochem, Woods
Hole, MA 02543
USA
Copyright © 2002 Institute for Scientific Information
===========
(14) AND FINALLY: CAUGHING A SIGH OF RELIEF AS CAR EXHAUSTS 'MAY
SLOW GLOBAL
WARMING'
>From Ananova, 19 February 2002
http://www.ananova.com/news/story/sm_524431.html?menu=news.scienceanddiscovery
A climate expert says global warming could be balanced out by the
cooling
effect of car exhausts.
He says aerosols pumped out by vehicles can lead to the formation
of rain
droplets in clouds which, in turn, has a cooling effect.
Computer climate models which predict global warming may not have
taken this
effect into account.
Ran Ramanathan, of the Scripps Institution of Oceanography in
California,
says aerosol output has increased by about a third since 1980.
The Times reports he has calculated that the cloud-seeding effect
of
aerosols could lower temperatures locally by up to 2.5C.
Aerosols are also produced by industrial processes and naturally
by
volcanoes but do have some negative health and environmental
effects.
Ramanathan said: "There is a possibility that it might add
more impact or
virtually balance all the impact of greenhouse warming."
Copyright 2002, Ananova
--------------------------------------------------------------------
CCNet is a scholarly electronic network. To
subscribe/unsubscribe, please
contact the moderator Benny J Peiser <b.j.peiser@livjm.ac.uk>.
Information
circulated on this network is for scholarly and educational use
only. The
attached information may not be copied or reproduced for any
other purposes
without prior permission of the copyright holders. The fully
indexed archive
of the CCNet, from February 1997 on, can be found at
http://abob.libs.uga.edu/bobk/cccmenu.html.
DISCLAIMER: The opinions, beliefs and viewpoints expressed in the
articles
and texts and in other CCNet contributions do not necessarily
reflect the
opinions, beliefs and viewpoints of the moderator of this network