PLEASE NOTE:
*
CCNet, 15 November 1999
------------------------------
QUOTE OF THE DAY
"The proxies indicate that a drier
climate prevailed in the
Shiyang River drainage during the last
glacial. Lake Yiema was
dry and eolian sand covered most part of
the lake basin. During
the early and middle Holocene, a moister
climate prevailed in
the drainage. Climate became dry
stepwise with an abrupt
transition from one stage to another
during the entire Holocene
and became driest since about 4,200 BP.
Maximum dry climate
spells occurred at about 12,000-10,000
BP and after about 4,200
BP.
-- F.H. Chen et al.
(1999) Environmental changes documented
by
sedimentation of Lake Yiema in arid China since the
Late
Glaciation
(1) "SURPRISE" METEOR SHOWER FAILS TO MATERIALISE
SpaceViews, 14 November 1999
(2) POSSIBLE ACTIVITY FROM COMET C/1999 J3 LINEAR
Rainer Arlt <rarlt@aip.de>
(3) FIREBALL OVER FLORIDA
Ron Baalke <baalke@ssd.jpl.nasa.gov>
(4) CRATERS YIELD CLUES TO ASTEROID'S HISTORY
Explorezone, 11 November 1999
(5) CRUSHING BLOW
Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
(6) AMS LEONIDS UPDATES
Jim Richardson <richardson@digitalexp.com>
(7) SEARCHING FOR CLUES TO PERIODICAL CLIMATE CHANGE
Andrew Yee <ayee@nova.astro.utoronto.ca>
(8) MORE ON THE 4000 BP EVENT
F.H. Chen et al., LANZHOU UNIVERSITY
(9) CHANGES IN LATE/MID HOLOCENE SHORELINES IN INDIA
A.S. Gaur & K.H. Vora, MARINE ARCHAEOL CTR
(10) EARTH SCIENCE GOES ONLINE
Andrew Yee <ayee@nova.astro.utoronto.ca>
(11) SPACE EDUCATION
H.H. von Muldau, PFIAT RES,ROSSDORF
=========
(1) "SURPRISE" METEOR SHOWER FAILS TO MATERIALISE
From SpaceViews, 14 November 1999
http://www.spaceviews.com/1999/11/14b.html
A new meteor shower predicted by some astronomers to be visible
last
week as a warmup to this week's Leonids failed to materialize,
with
only a few meteors noticed by observers.
The "surprise" shower, informally dubbed the Linearids,
was predicted
to be visible around November 11 when the Earth passed very near
the
orbital path of newly-discovered long-period comet C/1999 J3
LINEAR,
just 40 days after the comet was in the same area.
This orbital coincidence led some astronomers to predict the
possibility of a meteor shower, as dust left behind by the comet
in
its orbital path burned up in the Earth's atmosphere. This would
be
visible on Earth as a shower of meteors appearing to radiate from
the bowl of the Big Dipper in the constellation Ursa Major.
Reports disseminated through the Internet in the days after the
predicted peak of the Linearids, though, showed no signs of any
shower
observed by astronomers. Most only reported one or a few meteors
coming
from Ursa Major per hour.
This was not a surprise for some astronomers. Existing meteor
showers,
such as the Leonids, are associated with short-period comets,
rather
than the 63,000-year period C/1999 J3 LINEAR. Short-period comets
can
build up streams of dust throughout their entire orbital paths,
so that
the showers can be seen on an annual basis.
Some astronomers planned to use their observations of the
Linearids as
a warmup for the Leonids, an established annual meteor shower
expected
to peak on the night of November 17-18.
Interest in the Leonids has been high because of the intense
storms of
meteors seen approximately every 33 years, most recently in 1966.
Predictions for an intense storm last year fell through, with
peak
sustained counts of 340 meteors an hour, far less than the 1996
peak of
40 meteors per second.
Predictions for 1999 by astronomers Rob McNaught and David Asher
call
for a slightly greater peak rate of 500 meteors an hour, with
that peak
likely to be best visible in the early morning hours November 18
in
Europe.
The possibility of a meteor storm had caused concerns among
spacecraft
operators last year, who feared damage to their spacecraft by the
small
but high-speed meteors. In many cases they took steps to protect
their
spacecraft by orienting them to protect vulnerable areas, such as
solar
panels and electronics, and no damage to any satellites were
reported.
With no major storm forecast for 1999, and with the experience of
1998,
operators are expected to take similar measures to protect their
spacecraft, but with considerably less fanfare.
While no major storm is predicted for 1999, and forecasts for
2000 call
for only a minor shower, astronomers should keep an eye out for
2001
and 2002. The forecasts by McNaught and Asher predict up to
15,000
meteors per hour in 2001 and 25,000 per hour in 2002 as the Earth
passes through newer, denser regions of the dust trail in the
orbital
path of comet Tempel-Tuttle.
With no reports of major showers from the "Linearids",
astronomers now
turn their attention to this week's Leonids.
Copyright 1999, SpaceViews
==============
(2) POSSIBLE ACTIVITY FROM COMET C/1999 J3 LINEAR
From Rainer Arlt <rarlt@aip.de>
-------------------------------------
I M O S h o w e
r C i r c u l a r
-------------------------------------
Possible Activity from Comet C/1999 J3 LINEAR
A slight chance of meteor shower activity caused by debris from
Comet
C/1999 J3 (LINEAR) encouraged quite a few observers to check for
meteors from a radiant position near alpha=175deg, delta=+53deg
as
predicted from the orbit of the Comet.
No activity outburst occurred. The below list of individual ZHR
values
indicates weak activity all day on November 9, 1999, and in the
evening
hours of November 11 near the passage of the node of the comet's
orbit.
On several occasions the radiant elevation was too low for
a sensible
ZHR value. Due to possible contamination by sporadic
background
activity, the activity cannot be reliably associated with
particles
from the Comet.
Radar records from Ondrejov, Czech Republic, indicate enhanced
activity
between 21h and at least 3h UT on November 11/12 comared
with the day
before (see http://sunkl.asu.cas.cz/~stork/linearids.html).
The
activity is associated with faint meteors, possibly beyond the
visual
range. No clear enhancement appears in the forward scatter data
by
Kazuhiro Sizuki (see http://www.tcp-ip.or.jp/~kaze/data/htyk9911.htm).
-------------------------------------------------------------------------
Date Period UT LM LIN nonLIN hR
ZHR Observer
-------------------------------------------------------------------------
Nov 08 1335-1415 6.0 2
3 4 - Qi Rui (China)
Nov 08 1441-1528 6.0 0
6 0 Qi Rui
(China)
Nov 08 1620-1750 6.0 3
15 18 9 Qi Rui (China)
Nov 08 1830-2027 6.0 0
14 0 Qi Rui
(China)
Nov 09 0330-0430 5.1 0
3 0 Peter
Detterline (USA)
Nov 09 0746-0846 5.6 1
8 38 3 Peter Detterline (USA)
Nov 09 0846-0946 5.4 1
7 48 5 Peter Detterline (USA)
Nov 09 2220-2321 5.8 2
10 22 9 Alastair McBeath (UK)
Nov 09 2322-0022 5.8 2
10 26 8 Alastair McBeath (UK)
Nov 10 0022-0122 5.8 2
12 31 7 Alastair McBeath (UK)
Nov 10 0123-0228 5.8 0
18 0 Alastair
McBeath (UK)
Nov 10 0655-0755 5.1 0
8 0 Mark Davis
(USA)
Nov 10 0755-0855 5.2 0
8 32 0 Mark Davis (USA)
Nov 10 0855-0955 5.3 0
8 0 Mark Davis
(USA)
Nov 10 1830-1900 4.0 0
3 17 0 C.L. Chan (Hong Kong)
Nov 10 2200-0000 6.0 (3)
8 - Ulhas
Deshpande et al. (India)
Nov 11 0001-0107 5.7 0
12 21 0 Joseph Zammit (Malta)
Nov 10 2323-0423 5.9 7
55 32 4 Martin Galea (Malta)
Nov 11 0257-0424 6.0 2
17 48 3 Joseph Zammit (Malta)
Nov 11 0356-0508 6.0 0
7 44 0 Alfredo Pereira (Portugal)
Nov 11 0330-0715 5.8 1
9 ~0 - Mike Linnolt (USA)
Nov 11 0701-0801 5.3 0
7 0 Mark Davis
(USA)
Nov 11 0801-0921 5.4 0
10 0 Mark Davis
(USA)
Nov 11 1845-1913 5.8 0
2 0 Qi Rui
(China)
Nov 11 1900-2000 -
0 19
0 Peter Zimnikoval et al. (Slovakia)
Nov 11 1910-2015 6.1 1
7 15 5 Jurgen Rendtel (Germany)
Nov 11 1913-2014 5.8 1
12 40 3 Qi Rui (China)
Nov 11 1900-2100 4.8 0
5 2 - J. Marques, R. Afonso
(Portugal)
Nov 11 1900-2115 5.9 0
14 15 0 Frank Enzlein (Germany)
Nov 11 1900-2130 5.8 0
15 15 0 Nikolai Wuensche (Germany)
Nov 11 2115-2130 5.8 1
5 55 10 Qi Rui (China)
Nov 11 2200-2300 6.0 (5)
8 - Ulhas
Deshpande et al. (India)
Nov 12 0022-0320 6.0 2
33 32 2 Umberto Mule Stagno (Malta)
Nov 12 0020-0324 5.8 2
41 33 2 Joseph Zammit (Malta)
Nov 12 0020-0340 5.9 3
39 34 3 Martin Galea (Malta)
-------------------------------------------------------------------------
I would like to thank all the above observers for their efforts
and
swift reports, and I hope I did not overlook any message in this
busy
time before the Leonids.
Rainer Arlt, 1999 November 13
-----------------------------
NOTE: The WWW server of the IMO is down, probably until Monday,
for
unknown reasons. Its site is alarm secured and cannot be
accessed
before Monday. Please apologize for the inconvenience.
IMO-news messages should be directly sent to the distributing
server at: imo-news@eGroups.com
==================
(3) FIREBALL OVER FLORIDA
From Ron Baalke <baalke@ssd.jpl.nasa.gov>
Heavenly fireball puzzles Volusia County residents
November 12, 1999
DELAND, Fla. (AP) - A blue ball of fire that streaked across the
sky
above Volusia County has residents wondering whether the sight
was
something out of this world.
Clint Jones, who caught a glimpse of the hurling mass over DeLand
Tuesday night, is betting on a UFO.
'I believe it's possible,' Jones said from his home on the St.
Johns
River. 'I know they exist.'
Police scanners indicated a number of residents saw the blue
ball.
At 9:16 p.m., one anonymous caller told the Volusia County
Sheriff's
Office he saw a fireball pass over the intersection of Clyde
Morris and
LPGA boulevards. It was headed for Ormond Beach.
Sheriff's deputies, along with Daytona Beach police officers and
a
sheriff's helicopter, searched for more than an hour. They found
nothing.
The National Weather Service in Melbourne reported no unusual
activity
Tuesday night. Officials at the Federal Aviation Administration
tower
in Daytona Beach and the FAA Regional Office in Atlanta said they
saw
nothing out of the ordinary.
'If a pilot would have seen it, they would have reported it,' FAA
spokeswoman Kathleen Bergen said.
Roger Hoefer, curator of astronomy at the Museum of Arts and
Sciences
in Daytona Beach, speculated that people may have seen a Bolide
meteor.
Bolide meteors appear to be falling, when in reality, they're
simply
crossing the horizon.
'This was not falling,' Hoefer said. 'It was still moving in its
orbital path.'
=================
(4) CRATERS YIELD CLUES TO ASTEROID'S HISTORY
From Explorezone, 11 November 1999
http://explorezone.com/archives/99_11/12_mathilde_craters.htm
By Greg Clark, space.com . 11.12.99
When the Near-Earth Asteroid Rendezvous spacecraft flew past
Mathilde
in 1997, it returned several surprises to Earth.
By analyzing the deflection in the craft's flight path that the
asteroid's gravity caused, scientists calculated that Mathilde
had a
density only 30 percent greater than water.
Mathilde's low density surprised many planetary scientists
because
asteroids are thought to be composed of mostly solid, rocky
material.
The least dense of the asteroid samples that have fallen to Earth
as
meteorites are about 60 percent more dense than water. The most
persuasive explanation for the low density of Mathilde is that it
is
very porous.
More puzzling than the density, though, were pictures of giant
craters
that seemed completely free of surrounding debris. Craters are
one of
the ubiquitous physical features of the solar system, and almost
always
they are filled, covered and surrounded by the fragments of
material
called ejecta. This is the material that is excavated by an
impact,
explodes outward and then falls back to the surface, blanketing
the
area in and around the hole. In craters the size of Mathilde's,
but on
other asteroids, this ejecta is often kilometers deep. Mathilde,
however, is clean.
Now, laboratory modeling that simulates high-speed impacts that
might
have occurred on Mathilde shows that the craters could have been
punched in like dimples into a Styrofoam ball rather than
excavated
out.
Researchers at the Boeing Company's Shock Physics Group in
Seattle,
Wash. have found that under certain conditions, craters form in
porous
material by compressing it, rather than throwing it out. The
research,
lead by Kevin Housin, a research fellow at Boeing, is published
in this
week's issue of the journal Nature.
One of the unique characteristics of porous materials was noted
in the
1950s when the United States and Britain were testing atomic
weapons on
coral atolls in the Pacific Ocean. Craters in these very porous
corals
formed essentially by being crushed up as shock waves passed
through.
In these craters, virtually all the material was compacted, not
ejected.
This inspired the idea, Housen said, that perhaps the same kind
of
collapse might occur with impact craters on Mathilde if it really
is
very porous.
"Instead of forming a crater by digging a hole out and
throwing the
material around the crater. You basically just squish it up,
compact it
and compress it with very little ejecta being formed."
To test this idea, Housen and his colleagues used a high-speed
centrifuge with a hypervelocity gun mounted in the center.
Spinning the
centrifuge to produce an artificial gravity 500 times that of
Earth,
the team shot small nylon projectiles at a target material that
had the
same density as Mathilde.
"If you look at the physics of how craters form,"
Housen explained,
"and want to conduct a small-scale experiment that correctly
models a
very large crater on Mathilde, you have to form the crater at
elevated
gravity. You want to reproduce the weight of material that is
being
excavated on Mathilde."
Boosting the gravity makes a small amount of material behave like
a
much larger mass of material.
"You can think of it as a wind tunnel for impact
cratering," Housen
said. "People test the aerodynamics of how airplanes work by
making
very small scale models. But they adjust properties of the fluid
-- the
air that's flowing over them and the velocity so that they get
things
simulated in the right way.
"By doing this experiment at 500 times normal gravity we can
simulate
directly one of these large craters that form on Mathilde,"
he said. The
craters do indeed form without ejecta blankets.
Joe Veverka, who leads the imaging team for the NEAR spacecraft,
said
this kind of impact modeling is what is needed to explain
Mathilde's
curious craters.
The holes on Mathilde appear to have been formed right next to
one
another, without affecting each other at all. "We would
expect a huge,
catastrophic collision of this kind to cause major modification
to the
craters nearby, but we don't see this happening," said
Veverka, who is
chair of the astronomy department at Cornell University.
These very localized effects of large impacts suggest that
Mathilde is
made of something that dampens the shock of impact,
"basically like a
body made of shock absorbers," Veverka said.
People have suggested that a very porous body might be able to
dampen
the shocks of impacts so that one crater might form next to
another
without causing major landslides and such, Veverka said. This
sort of
explanation has only been a vague suggestion, never tested with
experimentation.
Cautioning that he had not seen the results of Housen's work,
Veverka
said that this type of study is necessary to figuring out how
Mathilde's craters formed.
The craters formed in Boeing's centrifuge also match Mathilde's
craters
in this sense. In the porous material, the affects of craters
remained
very localized. Craters could form right next to each other
without
disturbing one another, Housen said.
The impact craters Housen's team produced do remarkably resemble
those
found on Mathilde, but some scientists who have studied the
asteroid
worry that the compaction explanation for the craters may raise
more
questions than it answers.
William Merline, an astronomer at Southwest Research Institute in
Boulder, Colo. who studies asteroids, is one of those.
"It's a little hard to believe that you keep compressing the
thing and
it still has a density of 1.3 (grams per cubic centimeter),"
Merline
said. (Water has a density of 1 gram per cubic centimeter)
"It would
seem like you would have to start with an even-lower-density
body."
Mathilde's low density is hard enough to explain, Merline said.
It is
even harder to imagine a body so porous that its density is the
same
as water.
Housen, though, thinks that might be possible.
"If you calculate how much Mathilde should have compacted
just by the
formation of those large craters that you see, it turns out that
the
density might have been about 20 percent lower than what it is
now."
An earlier Mathilde, uncompressed by cratering, would have had a
density very close to that of water.
"People tend to think that when the solar system formed,
when you have
gas and dust settling down in a very quiescent kind of
environment, you
may tend to build up these fluffy kind of objects," he said.
"Unless
you get something that's fairly large -- much bigger than
Mathilde --
it won't have enough self gravity to really squish itself up
much."
Mathilde might be an early step in the evolution of heavier
asteroids,
Housen suggests. Perhaps after a few more billion years of
swinging
around the solar system and being pounded and compressed, it may
come
to resemble the more dense, less porous rocks that have landed
on Earth as meteorites.
Copyright 1999, Explorezone
==================
(5) CRUSHING BLOW
From Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
Nature News Service
Press Release: November 11, 1999
Crushing Blow
In June 1997, the Near Earth Asteroid Rendezvous spacecraft flew
past
the asteroid 253 Mathilde, sending back images of a
crater-battered
world about 52 kilometres in diameter, with five giant craters
each
over 20 km in diameter. Craters of such a size are generally
surrounded
by blankets of ejected material several kilometres deep, but on
Mathilde there are no signs of such material.
The asteroid's unusually low density is thought to be part of the
explanation for this lack of ejected material, and this is now
confirmed
by hypervelocity impact experiments carried out by Kevin R.
Housen
of The Boeing Company, Seattle, Washington, and colleagues. These
experiments -- which involve firing projectiles at very high
velocities
at samples of a porous material -- suggest that the craters are
produced
by compaction, rather than excavation. Such a compaction process
would
result in relatively little ejected matter being lost into space,
explaining
why material from highly porous asteroids is a rarity in
meteorites
reaching Earth.
Erik Asphaug of the University of California at Santa Cruz,
California
discusses these findings in an accompanying News and Views
article.
[NOTE: The News and Views article and full text of the paper are
available
at http://www.nature.com/cgi-bin/wbsp-home.cgi
. Click on the item
"Crushing blow (11 November 1999)".]
============
(6) AMS LEONIDS UPDATES
From Jim Richardson <richardson@digitalexp.com>
Hello colleagues,
Throughout the upcoming week, the American Meteor Society (AMS)
will be
maintaining a Leonids '99 Update page at the AMS web site,
located at:
http://www.amsmeteors.org/leo99update.html
The purpose of this page is to provide a narrative description,
along
with eyewitness accounts, of the 1999 Leonid meteor shower as
compiled
from reports received by the AMS and our affiliate group, the
North
American Meteor Network (NAMN). We are designing this page
to act as a
compliment to the reporting efforts and analysis of the
International
Meteor Organization (IMO), Dutch Meteor Society (DMS), and other
related groups. Although observed hourly rates and shower
characteristics will be given, we do not intend to offer a
detailed
analysis or ZHR profile (leaving this to the other groups).
Instead,
we intend to compile a historical record of selected anecdotal
accounts
and personal impressions of the 1999 Leonids.
Many of the accounts included on this page will undoubtedly come
from
the MeteorObs mailing list, but we would *greatly* appreciate
receiving
reports from all of the various professional and amateur Leonid
expeditions worldwide. If you would like to send us a narrative
account
of your personal Leonid experience, in addition to the scientific
data
collection which you are doing, I can receive your reports at the
below
email address:
Jim Richardson <richardson@digitalexp.com>
Selected narratives will be posted on the AMS web site as quickly
as
possible, in addition to commentary on the overall shower
activity,
with a final edited collection of Leonid accounts to appear in
the next
issue of the AMS journal, Meteor Trails. This was done with
good
success last year, and it is hoped that these historical
narratives
will prove to be a enjoyable companion to the numerous scientific
studies being performed.
Best regards,
Jim
James Richardson
Department of Physics
Florida State University (FSU)
Operations Manager
American Meteor Society (AMS)
http://www.amsmeteors.org
================
(7) SEARCHING FOR CLUES TO PERIODICAL CLIMATE CHANGE
From Andrew Yee <ayee@nova.astro.utoronto.ca>
Office of Public Affairs
Columbia University
New York
November 8, 1999
Deep Ocean Current 'Seesaw' May Relate To Global Warming/Cooling
Cycle
By Kurt Sternlof
In a display of far-reaching scientific opportunism and
synthesis,
Lamont-Doherty Earth Observatory marine geochemist Wallace
Broecker and
colleagues have used data on the distribution of an
ozone-depleting
pollutant to shed light on a deep ocean mystery that could affect
our
understanding of global warming.
Their paper on the subject appears in the November 5th issue of
Science.
Deep ocean circulation is dominated by two "rivers" of
sinking
seawater, Broecker explained. One deep-water source originates in
the
North Atlantic, the other off the coast of Antarctica. In this
way all
the water in the oceans is ventilated at the surface and mixed at
depth
about once every 800 years.
The mystery lies in the fact that different chemical tracer
methods for
measuring the rate of deep-water formation have yielded different
results -- a faster rate over the long term and, more recently, a
slower rate for the Antarctic source -- while other evidence
suggests
that deep ocean circulation runs at a steady rate, with roughly
equal
inputs from north and south over the 800-year mixing cycle.
Broecker's team turned to data on the pollutant
chlorofluorocarbon-11,
better known as freon, to double-check the recent rates of
deep-water
formation. Freon makes a perfect tracer, because it disperses
quickly
in the atmosphere, is highly soluble in water, can be measured
very
accurately, and was released only recently. Thus, the levels of
freon
in deep-water samples provide a measure of how much surface water
has
subsided to the depths over the past few decades.
The freon data was analyzed in a study led oceanographer
Alejandro Orsi
of Texas A&M University.
According to Broecker's reading of that study, the current rate
of
Antarctic deep-water formation is only one-third that of the
North
Atlantic, where the rate matches the expectations of a
steady-state
scenario. The freon data also suggests that no other significant,
as
yet undiscovered deep-water source areas exist. Accommodating all
the
data suggests to Broecker that the rate of Antarctic formation
must
have changed dramatically over the last 800 years, from fast to
slow.
"If I'm right, deep ocean circulation is not steady state
process. That
concept is mind-boggling, and certainly open to debate,"
Broecker said.
"But it's reasonable to wonder whether deep ocean
fluctuations could be
related to fluctuations in global climate. The potential
consequences
of that are enormous, and provide a lot of fodder for scrutiny
and
further research."
Broecker believes that such a relationship does exist. After all,
scientists have demonstrated that El Nino cycles are strongly
tied to
fluctuations in the patterns of shallow ocean currents. Why
wouldn't
changes in deep ocean currents also express themselves
climatically? He
finds it tantalizing to look at the evidence for the Antarctic
slow-down and consider the possibilities.
Of particular interest is the relationship between the new data
and
three well-established climatic phenomena.
First, that about 12,500 years ago deep-water formation in the
north
virtually ceased during a pronounced cold event, while Antarctic
deep-water formation accelerated in conjunction with a relative
warming
there. Second, that pronounced ice-rafting events related to
cyclical
warming trends occur in the North Atlantic every 1,500 years. And
third, that a cooling event called the "Little Ice Age"
occurred
between 1350 and 1880, since which the planet has warmed in two
roughly
equal steps -- from 1880 to 1945 and from 1975 to present.
Within all this, Broecker sees the possibility that deep-water
formation continues to seesaw from north to south in association
with
temperature changes on a 1,500-year cycle. If true, regardless of
the
mechanism by which deep ocean currents affect climate, natural
global
temperature changes can be expected to occur on a millennial time
scale. The question then becomes -- are we now in the midst of
just
such a natural temperature shift and, if so, what would today's
climate
be like in the absence of greenhouse warming?
"There's really no way we can tell at this point. It is just
as likely
that natural forces currently retard the effects of greenhouse
warming
as enhance it," Broecker said. "We don't know enough
about these
natural climate shifts or how quickly they occur to be able to
predict."
Broecker does believe that the key to understanding humanity's
role in
the current global warming trend lies in unraveling the demise of
the
Little Ice Age -- what part of the two-step warming since 1880 is
due
to greenhouse gases versus natural forces. And he hopes that his
paper
will stimulate more interest and research in that direction.
That further research might disprove his notion of a deep ocean
cycle
tied to climate is fine with Broecker. However, to those of his
colleagues who would attribute the current global warming trend
entirely to such natural causes, he says nonsense.
"It is ridiculous to argue that greenhouse gases are having
no effect,"
he said. "The preponderance of evidence that they are
warming the
planet is overwhelming, regardless of any underlying natural
trend."
==============
(8) MORE ON THE 4000 BP EVENT
F.H. Chen*), Q. Shi, J.M. Wang: Environmental changes documented
by
sedimentation of Lake Yiema in arid China since the Late
Glaciation.
JOURNAL OF PALEOLIMNOLOGY, 1999, Vol.22, No.2, pp.159-169
*) LANZHOU UNIVERSITY,DEPT GEOG,LANZHOU 730000,GANSU,PEOPLES R
CHINA
In this study, a 6 m long core (16,000 BP) at the center of the
dry
Lake Yiema, a closed lake of Shiyang River drainage in Minqin
Basin of
the arid northwestern China, was retrieved to recover the history
of
climate changes and lake evolution in the area. Five radiocarbon
dates
on organic matter were obtained. A chronological sequence is
established based on these five dates and other dates from nearby
sites. Magnetic susceptibility, particle size and chemical
composition
were analysized for climate proxies. The proxies indicate that a
drier
climate prevailed in the Shiyang River drainage during the last
glacial. Lake Yiema was dry and eolian sand covered most part of
the
lake basin. During the early and middle Holocene, a moister
climate
prevailed in the drainage. Climate became dry stepwise with an
abrupt
transition from one stage to another during the entire Holocene
and
became driest since about 4,200 BP. Maximum dry climate spells
occurred
at about 12,000-10,000 BP and after about 4,200 BP. A dry climate
event
also existed at about 7,600 BP. Periodical sand storms with about
400-yr cycle happened during the middle Holocene. Desiccation
processes
of the lake started at 4,200 BP, and were accelerated since the
last
2,500 yrs by the inflow water diversion for agriculture
irrigation.
During the past 2,500 yrs, the lake size has been closed
associated
with the human population, implying that the human impact has
been
accelerating the lake desiccation superimposed on the natural
climate deterioration. Copyright 1999, Institute for Scientific
Information Inc.
==========
(9) CHANGES IN LATE/MID HOLOCENE SHORELINES IN INDIA
A.S. Gaur*) & K.H. Vora: Ancient shorelines of Gujarat,
India, during
the Indus civilization (Late Mid-Holocene): A study based on
archaeological evidences. CURRENT SCIENCE, 1999, Vol.77, No.1,
pp.180-185
*) MARINE ARCHAEOL CTR,NATL INST OCEANOG,PANAJI 403004,GOA,INDIA
Changes in the shoreline at any point could be due to various
reasons
such as tectonic disturbance or shift in sedimentological regime
causing erosion or deposition. Many scientific investigations,
focusing
on the palaeo-shoreline vis-a-vis sea level fluctuations in India
based
on numerous geological techniques, have indicated that at about
6000
BP, the sea level was approximately 6 m higher than at present
and
about 4000 years BP it stabilized at the present one with minor
fluctuations. Copyright 1999, Institute for Scientific
Information Inc.
==============
(10) EARTH SCIENCE GOES ONLINE
From Andrew Yee <ayee@nova.astro.utoronto.ca>
Office of Public Affairs
Columbia University
New York
November 5, 1999
Another Innovative On-line, Multi-media Resource -- Columbia
Earthscape
-- Launched by Columbia
By Lauren Marshall
In a bold departure from its paper counterparts -- scientific
journals
that reproduce their print editions on-line -- Columbia and
Columbia
University Press have launched Columbia Earthscape, the first
multi-media resource in the earth sciences designed for
scientists and
laymen alike.
Described as one-stop shopping in the field of earth system
science,
Columbia Earthscape contains current research, breaking news,
policy
debates and curriculum models for Earth science teachers on a
wide-range of topics, such as climate change, oceanography,
geology,
and environmental resources.
The site contains of over 70,000 pages of multi-media web
content,
including full-text books, video clips, current journal
articles,
lectures and seminars, conferences, policy papers and commentary,
maps
and models, searchable databases, links and live web-casts of
important
conferences, from a variety of sources -- among them, Columbia,
NASA,
MIT, the American Museum of Natural History and ABC News.
On Nov. 15 and 16, Earthscape will feature a live webcast of
Lamont
Doherty Earth Observatory's The State of the Planet conference,
which
will assess the state of the Earth from four standpoints:
climate,
natural resources, natural hazards and humankind's impact on the
planet.
As the Earthscape site matures, 2,000 pages of information will
be
added monthly.
By virtue of its medium, the World Wide Web, it is expected that
Earthscape will transform the way researchers, scholars,
teachers,
students and decision-makers gain access to critical information
in the
Earth sciences and environmental policy. The virtual publication
is
expected to reduce the cost of scholarly information access and
use,
and to expand the dissemination of scientific research to a wide
audience. It also has the potential to create a trend in on-line
curricular support for teachers in the field.
According to John Haber, editor of Columbia Earthscape, the site
was
developed with scientists in mind, but is not exclusively for a
scholarly audience.
"Because science and environmental policy intrude on
people's lives on
a daily basis, the site offers something for everyone," said
Haber.
A quarterly on-line magazine Earth Affairs offers a forum for
scientists to exchange opinions and ideas. Breaking news engages
the
general public, and while the site offers information in the
earth
sciences for students, curriculum modules offer classroom tools
for
science teachers.
"Earthscape provides an environment for experimentation in
the science
curriculum thereby creating a community of teachers who are using
high-tech multimedia materials in the classroom," said
Haber.
In addition to curriculum modules in eight areas of the earth
sciences,
the site provides course models for others to follow, guidance on
how
to approach particular issues in the classroom and ways to
further
integrate current research and policy into undergraduate course
curriculum.
"With Earthscape we are attempting to bring easily
searchable quality
content in a variety of media from a variety of resources,"
said Kate
Wittenberg, senior executive editor of Columbia University Press
and
director of the Electronic Publishing Initiative at Columbia.
"In a
university setting, because of our resources and expertise, we
can move
swiftly and innovatively in the creation of interesting new
models for
publication."
Columbia Earthscape is the newest scholarly publication in a
generation
of innovative, interdisciplinary digital publications developed
by
Columbia. Through the Electronic Publishing Initiative at
Columbia (the
EPIC Center) established this summer, innovative on-line
publications
are explored, developed, and evaluated as digital solutions to
the
current crisis in scholarly publication: growing publishing costs
in a
shrinking market for scholarly books.
Like Columbia International Affairs On-line, the first
multi-disciplinary on-line venture of its kind in the field of
International Affairs, which was launched by Columbia two years
ago,
Columbia Earthscape is the result of a collaborative effort
between the
Columbia University Press, the University Libraries, and Academic
Computing Information Systems (AcIS).
"The groundwork for Earthscape was set when we began
planning for the
Columbia Digital Library. This work gave us much insight into the
viability of on-line resources in academic settings," said
Elaine
Sloan, vice president for Information Services and University
librarian. "Since that time, our commitment to the
development of the
digital library has grown. One of the outcomes is the creation of
EPIC,
an organization that draws from the expertise of a range of minds
within the University: faculty who create knowledge, information
technologists who create the complex architecture and security of
EPIC
sites, librarians who contribute their expertise in the
collection and
organization of information, and Columbia University Press'
contributions as publishers."
In addition to a start-up grant from the Office of the Provost,
Columbia Earthscape has received two three-year grants assisting
in the
development, launch and staffing of the publication, including
$590,000
from the National Science Foundation's Digital Library 2 Program
and
$200,000 from SPARC, the Scholarly Publishing and Academic
Resources
Coalition. According to the Director of SPARC, Rick Johnson,
Earthscape
was one of three digital initiatives awarded grants because of
their
"enormous potential to transform the scientific information
economy"
and "general benefit to science, academe and society at
large."
Columbia Earthscape, located at www.earthscape.org, is accessible
to
the Columbia community free of charge via Columbia Net. The site
will
be available for subscription to both institutions and
individuals in
mid-December.
For more information on digital projects at Columbia contact Kate
Wittenberg at (212) 666-1000, ext. 7119 or kw49@columbia.edu or visit
the earthscape site at http://www.earthscape.org.
=============
(11) SPACE EDUCATION
H.H. von Muldau*): Space education, a tool to influence the
cultural
development in the society. ACTA ASTRONAUTICA, 1999, Vol.44,
No.7-12
SISI, pp.803-807
*) PFIAT RES,ROSSDORF,GERMANY
Culture is an organized group of learned responses of a
particular
society, or the total round of human activities, not due to
heredity, shared by members of a group. This means that culture
is
a dynamic process and it is in tight relationship to the
civilization as a tool to master their all day's tasks. Space
science is a result of the shift from the mass production
civilization to the knowledge civilization. The science had
opened
new ways of thinking into a new environment, space. The ability
to
develop thinking to new living areas is already a Learned
response
to the environment and therefore an act of culture. The next
changes in culture are a result of the different view, mankind
has
From earth looking back out of the spacecraft window. We see now
with other eyes the small and vulnerable living area of mankind.
We see no political limits partitioning the surface. We
understand
time zones as systems properties of the regions. This has up to
now influenced big groups of the societies. As this view has to
be
shared by all members of the societies in the same mode, space
education has to organize this effect. (C) 1999 Published by
Elsevier
Science Ltd. All rights reserved.
----------------------------------------
THE CAMBRIDGE-CONFERENCE NETWORK (CCNet)
----------------------------------------
The 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
*
LETTERS TO THE MODERATOR - CCNet, 15 November 1999
--------------------------------------------------
(1) SHOVING AROUND FLUFFY ASTEROIDS
Erik Asphaug <asphaug@es.ucsc.edu>
(2) DEFLECTING FLUFFY ASTEROIDS
Terry Richardson <richardsont@cofc.edu>
(3) HOYLE & WICKRAMASINGHE’S “COSMIC WINTER”
HYPOTHESIS
Duncan Steel <D.I.Steel@salford.ac.uk>
(4) COMETARY DUST LOADING
Bill Napier <wmn@star.arm.ac.uk>
=========
(1) SHOVING AROUND FLUFFY ASTEROIDS
From Erik Asphaug <asphaug@es.ucsc.edu>
Dear Benny,
Roy Tucker is right, that a low-density object is easier to
"shove
around" than a high-density object, all things being equal.
However
it's not as simple as that, since the material and structural
properties themselves determine how energy and momentum are
coupled to
a target.
For example, Stan Love and colleagues once fired identical
bullets into
cylinders of glass, and into cylinders of sintered glass beads.
Where
the aggregate targets formed a modest crater, the homogeneous
(and
more dense) targets flew apart into scattered fragments. We are
basically seeing the same thing in our asteroid impact models.
With regard to shoving asteroids around, it should be remembered
that
an explosion does not contribute momentum directly. Rather,
pieces
flying away at high speed cause the equal but opposite rebound
that
diverts the asteroid. (In laboratory impact experiments, it is
not uncommon for the largest remaining fragment to be moving
_towards_
the rifle, because of fragments ejected from its back
side!) If very
little material escapes the "ground zero", there will
be
correspondingly little change in the asteroid's momentum.
So the bottom line is, a very porous asteroid might be difficult
to
divert or disrupt by standard ("Deep Impact" or
"Armageddon") methods.
On the other hand, its low density would make it easier to divert
by
direct momentum coupling, e.g. by a solar sail, by kinetic mass
excavation, or by localized thermal devolatilization
(outgassing),
given enough advance warning. The notion of a standoff burst, as
explored by Al Harris and Tom Ahrens, also has promise, and
needs to
be revisited for highly porous, probably compactible surfaces.
We would be fools, of course, not to take our time to thoroughly
understand asteroids before implementing any idea which might
involve
gigaton warheads in space. This is no emergency, and missions
such as
Deep Impact are the perfect type of necessary exploration at this
stage.
Whether asteroids are "flying Rice Krispie treats" -- a
colorful
(flavorful?) description of the type of hyperporous, compactible
bodies
proposed by Housen et al. in this week's issue of Nature -- or
some
other kind of structure, my first recommendation is for those
curious
about such mechanisms to go to the article itself (available at
most
news stands) and references therein, rather than settling for
filtered
news content which of necessity simplifies a complex story.
My second recommendation is for the public to speak up for
missions
which will probe the physical nature of asteroids and
comets. They are
strangely difficult to understand, and more intricate than we
have yet
imagined.
Erik Asphaug
University of California, Santa Cruz
asphaug@es.ucsc.edu
================
(2) DEFLECTING FLUFFY ASTEROIDS
From Terry Richardson <richardsont@cofc.edu>
Dear Dr. Peiser,
Fluffy asteroids provide an alternate means of deflection should
one be
aimed at the earth and we reach the level of technology to
deflect
asteroids. Based on the idea of an ion engine where a small
amount of
mass propelled continuously over a period of time can accelerate
a
rocket to high speeds, a mechanism could be landed on such an
asteroid
that launches parts of the asteroid into space, reloads and
continues
to do so gradually deflecting the orbit away from the earth.
Perhaps a
longer lead time might be necessary in the discovery of such
asteroids
to employ such a system, but loosely organized material of the
right
nature should make such a system possible.
Sincerely,
Terry Richardson
Department of Physics and Astronomy
College of Charleston
Charleston, SC 29424
pager #937-1048
843 953-8071 phone
843 953-4824 fax
http://www.cofc.edu/~richardt/
==============
(3) HOYLE & WICKRAMASINGHE’S “COSMIC WINTER”
HYPOTHESIS
From Duncan Steel <D.I.Steel@salford.ac.uk>
Dear Benny,
The 19th century mathematician Augustus De Morgan, who was
Secretary of
the Royal Astronomical Society, wrote that one can tell the true
paradoxer by the extent to which he (De Morgan would write only
'he'
despite being the tutor of Ada Byron) had or had not studied the
work
which had previously been done on some topic of mathematics or
natural
science. That is, had the paradoxer read and understood the
literature?
In my review in Sky and Telescope I wrote that Hoyle and
Wickramasinghe
had published their hypothesis in 1978. I was working from memory
when
I wrote that, but it took me less than 60 seconds to find the
full details plus
abstract via the internet:
-------------------------------------------------
F. Hoyle and N.C. Wickramasinghe: Comets, ice ages, and
ecological
catastrophes. Astrophysics and Space Science, volume 53, number
2, pp.
523-526 (1978).
Abstract:
A total mass of the order of 10 to the 14th power grams added to
earth's upper atmosphere in the form of small particles of high
albedo
for visual wavelengths would produce an inverse greenhouse
effect,
shielding ground level from sunlight but permitting infrared
radiation
from the ground to escape into space. Such a mass of small
particles
might be acquired by earth in a close approach to a cometary
nucleus.
Ice ages and ecodisasters, such as that which occurred 65 million
years
ago, could arise from the effects of such an addition of
small
particles.
-------------------------------------------------
Now, the authors may well have been wrong in their hypothesis and
analysis, but that requires them to be judged on what they
did/wrote
and *not* on what some others may just think that they did/wrote.
To
that extent recent messages discussing the dust and/or sulphur
injected
into the (lower) atmosphere by volcanic eruptions has no bearing
upon
the question in hand, which pertains to the possible climatic
effects
of the deposition of substantial amounts of cometary dust into
the
upper atmosphere/mesosphere, where the physics involved is quite
different. If one is interested in the question, why not simply
look up
the Hoyle and Wickramasinghe paper and see what is involved?
Duncan Steel
==============
(4) COMETARY DUST LOADING
From Bill Napier <wmn@star.arm.ac.uk>
Dear Benny,
Lack of time doesn't allow me to do justice to your query (I'm on
leave
trying to meet a deadline for another novel!). However I can
comment
briefly on the basic astronomical model for dusting. We should be
thinking, not in terms of 20 km single-flyby comets, but rather
of
100-200 km diameter comets thrown into short-period,
Earth-crossing
orbits. These yield repeated stratospheric dustings with cyclic
inputs
on various scales, and also a zodiacal cloud with a mass enhanced
by
two orders of magnitude or so over periods of many millennia.
Giant
comets are easily the dominant mass input to the inner planetary
system
on say 100,000-year timescales.
There are now quite a few papers in the refereed literature, by
various
authors, showing that significant atmospheric perturbations are
expected. This is a very active area, relevant to many academic
disciplines as well as Spaceguard, and papers will be along in
due
course.
Best regards
Bill Napier
-----------------
CCNet-LETTERS is the discussion forum of the Cambridge-Conference
Network. Contributions to the on-going debate about near-Earth
objects,
the cosmic environment of our planet and how to deal with it are
welcome. The fully indexed archive of the CCNet, from February
1997 on,
can be found at http://abob.libs.uga.edu/bobk/cccmenu.html