PLEASE NOTE:
*
CCNet DIGEST, 14 December 1998
------------------------------
(1) LARGE SCALE IMPACT EVENT MAY HAVE TRIGGERED EXTINCTIONS IN
ARGENTINA 3 MILLION YEARS AGO
Bob Kobres <bkobres@arches.uga.edu>
(2) COSMIC DUST MAY TRIGGER ICE AGES
San Francisco Examiner
http://www.abcnews.com/sections/science/DailyNews/spacedust981210.html
(3) GLOBAL ANALYSIS OF LEONIDS AVAILABLE
Rainer Arlt <rarlt@aip.de>
(4) RADIATION BELT AROUND EARTH ADVERSLY AFFECTING SATELLITES
Andrew Yee <ayee@nova.astro.utoronto.ca>
=========================
(1) LARGE SCALE IMPACT EVENT MAY HAVE TRIGGERED EXTINCTIONS
IN
ARGENTINA 3 MILLION YEARS AGO
From Bob Kobres <bkobres@arches.uga.edu>
I called Pete and the word 'small'--that I questioned in the
earlier
note--should be changed to 'just large' as it is below.
bobk
From:
http://www.brown.edu/Administration/News_Bureau/1998-99/98-052.html
36 types of animals disappeared 3.3 million years ago Study
associates asteroid or comet impact with extinctions in Argentina
A
paper in Science magazine proposes that a major
ecosystem-altering
asteroid or comet impact took place 3.3 million years ago - a
geologically recent time - in what is now Argentina.
--------------------------------------------------------------------------------
PROVIDENCE, R.I. -- A new study shows that a previously unknown
impact from an asteroid or comet coincides with the disappearance
of
35 different types of ancient mammals and a flightless bird 3.3
million years ago. The impact may have directly caused the
regional
extinctions or triggered a climate change that led to the
disappearance of the animals in what is now southeastern
Argentina.
The findings may provide an opportunity for scientists to study
the
cause and effect of an event that wiped out animal life similar
to
species on Earth today.
"Unlike what impacts did to dinosaurs and other prehistoric
creatures, this was not an event that led to global
extinctions,"
said principal investigator Peter Schultz, professor of
geological
sciences at Brown University and an impact specialist.
"We've found
something linked to much more recent land history. The advantage
to
studying something this young is that you can really examine the
forensics.
"This is a threshold event. It may have been just large
enough to
cause regional damage and extinctions and may have triggered a
climate change. El Niņo or a volcanic eruption produces small
tweaks
to the climate compared to what one of these impacts can
do." The
cyclical cooling of the Earth's temperatures that began soon
after
the impact 3.3 million years ago continues today, he said.
The study is published in this week's Science magazine. Its
co-authors are Argentinean scientists Marcelo Zarate and Cecilia
Camilion; Willis Hames, an Auburn University geologist; and John
King, a researcher in the Graduate School of Oceanography at the
University of Rhode Island. The team studied an 18-mile-long
narrow
layer of greenish glass and red brick-like materials found in the
high ocean cliffs of southeastern Argentina. Called escoria, the
glass had puzzled scientists since it was first described in
1865.
[Editors: A color image of the escoria is available at the News
Bureau's web site.]
The glass and surrounding red-baked powder bear the signatures of
a
powerful ancient blast archived in the thick Argentine dust, say
the
researchers. They describe a half-dozen physical signs, from the
twisted and folded shapes of the glass to its isolation from
other
potential sources such as volcanoes. Chemical analysis of the
glass
produces all the right impact signatures: unusually high levels
of
magnesium oxide and calcium oxide, significant amounts of iridium
and
chromium, and only the tiniest traces of water.
The study shows the glass occurs just below a layer of dusty
deposits
containing fossil evidence of a 3-million-year-old disappearance
of 36
local types of animals. Extinct species include large
armadillo-like
creatures, ground sloths, hoofed groups of related mammals and a
flightless carnivorous bird. Other fauna later appeared in their
place.
By using a laser fusion technique to measure heavy to light argon
atoms in the glass, and by comparing the magnetic readings of the
glass layer to published records of magnetic-field changes over
the
eons, the researchers date the glass as 3.3 million years old,
just
prior to the extinctions.
Using research by other scientists that compared heavy to light
oxygen isotopes in sediment cores from the nearby ocean floor,
Schultz and colleagues offer evidence of a sudden drop in both
atmospheric and water temperatures almost 3.3 million years ago.
The
finding indicates that a climate change occurred shortly after
the
glass appeared and just prior to the animal life turnover.
"This research is analogous to comparing several time
clocks," said
Schultz. "We compared a clock in the glass to a clock in the
soil to
a clock in the deep-sea cores. This told us the conditions at the
time. We were surprised to find that the appearance of the
glasses
and the turnover of the fauna coincided with a temperature
drop."
The research began as a simple project to determine the origin
and
age of the escorias. However, the work identified a series of
coincidences that strongly suggest a major, ecosystem-altering
event
took place relatively recently, geologically speaking, he said.
=========================
(2) COSMIC DUST MAY TRIGGER ICE AGES
From San Francisco Examiner
http://www.abcnews.com/sections/science/DailyNews/spacedust981210.html
Space Dust Ice Age Trigger?
May Dim, Cool Earth Every 100,000 Years or So
S A N F R A N C I S C O, Dec. 10 —
The sky is falling—literally
in the form of dust, dropping to Earth from outer space.
This rain of particles may vary in cycles, periodically dimming
sunlight and cooling Earth. The variations may partly trigger ice
ages every 100,000 years or so, some scientists think.
But others are skeptical—at least until better data come in,
they
said Tuesday at the American Geophysical Union conference in San
Francisco. So in a sort of scientific spring cleaning,
researchers
are plumbing the ocean floor and flying into the upper atmosphere
to
collect dust that has fallen to Earth over millions of years, or
that
is falling right now through the atmosphere perhaps right past
your
eyes.
Like Popcorn Underneath the Couch
In high resolution images, these “interplanetary dust
particles”
vaguely resemble stale popcorn. Scientists hope the particles
will
tell us about Earth’s climate history and outer space.
One scientist even collects outer space particles that drop onto
rooftop collectors atop a building at Caltech in Pasadena. But
given
Los Angeles’ notorious smog, a rooftop collector isn’t
ideal “because
of all the gunk from the sky that falls on it,” admits the
researcher, space scientist Kenneth A. Farley.
Noted UC-Berkeley space scientist physicist Richard A. Muller has
argued for years that Earth’s pendulum-like swings between
glacial
and warmer conditions might be caused, in part, by our planet
swinging into and out of the solar system’s dust belts.
“Someone said this is a wonderful session because none of
the
speakers agree with any of the other speakers,” Muller joked
during
his talk at a half day symposium titled, “Accretion of
Extraterrestrial Matter Throughout Earth’s History.”
Passing Through the Dust Rings
Cyclical variations in the inclination of Earth’s orbit
cause it to
pass in and out of solar system dust rings sloughed off giant
rocks
some as big as cities, others the size of small states—called
asteroids, Muller says. Over time, these rings slowly drift
toward
the inner solar system and periodically encounter Earth. Muller
suspects Earth’s encounters with the rings partly account
for an
apparent 100,000-year cycle in ice ages.
Is the 100,000year cycle real, or a statistical illusion like so
many
natural “cycles” that scientists have reported for
centuries?
(An infamous example is a purported—but false—link
between sunspot
activity and crop prices, reported by scientists in the early
19th
century.)
Computer Model Shows Cycles
The 100,000-year cycle is real, at least if Steven J. Kortenkamp’s
data are right. The Carnegie Institution of Washington researcher
used computer models to show how dust would flow into the inner
solar
system by flaking off three “families” of asteroids
known as Eos,
Themis and Koronis. His computer model implies that over the last
1.2 million years, “the accretion rate of asteroidal dust
varies …
with a 100,000-year periodicity.”
But other scientists say it’s too early to credit the
invisible dusty
downpour for the ice ages—those semi-global freezes that
buried much
of North America under ice sheets miles thick, lowered sea
levels,
and enabled the ancestors of Native Americans to cross from
Siberia
into the New World. The last ice age ended roughly 10,000 years
ago,
just before the mass peopling of the Americas and the rise of the
great ancient civilizations of the Middle East.
Contrary to Muller’s thesis, there is no evidence that waves
of
interplanetary particles peak every 100,000 years, another
scientific
team was scheduled to announce at the conference.
The team members, Tom Trull and Will Howard of Australia, and
Bernard
Marty of France, dated the age of particles found in primeval
sediments by illuminating them with lasers. This technique
allowed
them to measure the particles’ abundance of an isotope
called
helium3, which is common in space particles. They found no
evidence
of a 100,000-year periodicity in the volumes of particles that
have
dropped to Earth over time.
Some scientists suspect the periods are real but have a more
down-to-Earth cause—namely, variations in oceanic processes
that
cause helium3 rich particles that clump together in certain
portions
of sediments.
Copyright 1998 Scripps Howard News Service.
========================
(3) GLOBAL ANALYSIS OF LEONIDS AVAILABLE
From Rainer Arlt <rarlt@aip.de>
Dear meteor astronomers,
A first comprehensive global analysis of the 1998 Leonids
will be published in the December issue of WGN, the journal
of the IMO. An HTML version is available from the homepage
http://www.imo.net. Below is the
abstract of the paper.
Kind regards, Rainer Arlt
----------------------------------------------
Bulletin 13 of the International Leonid Watch:
The 1998 Leonid Meteor Shower
----------------------------------------------
Rainer Arlt
Abstract:
---------
An overview of the 1998 Leonid activity is given based on visual
records from 217 observers who saw more than 47000 Leonids in 858
observing hours. A broad component rich in bright meteors
(background
component) was found to have its maximum at lambda=234.52 degrees
(eq.
J2000; 1998 November 17, 1h 40m UT) with ZHR=340+-20. The actual
`storm' component of the Leonid meteroid stream turned out to be
weak
in 1998 with a peak at lambda=235.308 degrees (1998 November 17,
20h
30m UT) reaching ZHR=180+-20. The first component is
characterized by
an extremely low population index of r=1.19 +-0.02 at
lambda=234.43
(1998 November 16, 23h 30m UT), whereas relatively high values of
r=2.00+-0.05 are found between lambda=235.15 degrees and
lambda=235.32
degrees (1998 November 17, 16h 40m - 20h 50m UT). The full
width at
half maximum of the background component is 17 hours, that of the
`storm' component is 0.75 hours. The data indicate a strong
dependence
of observable rates from the zenith distance through other than
geometrical effects.
(The paper can be downloaded from http://www.imo.net)
===================
(4) RADIATION BELT AROUND EARTH ADVERSLY AFFECTING SATELLITES
From Andrew Yee <ayee@nova.astro.utoronto.ca>
Office of Public Relations
University of Colorado-Boulder
354 Willard Administrative Center
Campus Box 9
Boulder, Colorado 80309-0009
(303) 492-6431
Contact:
Daniel Baker, 303-492-4509
Jim Scott, 303-492-3114
Radiation Belts Around Earth Adversly Affecting Satellites
Much of the energetic electron activity in Earth's radiation
belts, once
thought to be generated by the sun and solar wind, actually is
accelerated
to light-speed by Earth's own magnetic shell, creating periodic
havoc with
satellites.
Daniel Baker, director of the University of Colorado at Boulder's
Laboratory for Atmospheric and Space Physics, said new findings
indicate that electrons in the Van Allen radiation belts circling
Earth are energized to speeds much higher than researchers had
thought. The Van Allen belts are two main zones in Earth's
magnetosphere where charged particles are confined by the
planet's
magnetic fields.
"We used to think that the Van Allen Belts slowly waxed and
waned and
were not particularly dynamic," he said. "But these
belts have now
been shown to be powerful, energetic particle accelerators,
generating excitement and awe in the scientific community."
Named for physicist James Van Allen who discovered them in 1958,
the
belts consist of two doughnut-shaped regions containing electrons
and
protons centered thousands of miles above Earth's surface.
Speeding particles in the near-Earth environment from the sun,
solar
wind and Earth's magnetosphere -- commonly known as "killer
electrons" -- have had a dramatic effect on human
technological
systems, said Baker. "This includes many of the satellites
that are
up there now and future spacecraft like the space station, which
have
the potential to be severely impaired electronically by
light-speed
electrons."
Baker presented his latest findings at the fall meeting of the
American Geophysical Union held Dec. 6 to Dec. 10 in San
Francisco.
A paper authored by Baker and colleagues in the Oct. 6 issue of
Eos,
a publication of AGU, indicate an intense flux of electrons from
Earth's magnetosphere likely played an important role in the
failure
of the Galaxy 4 spacecraft last May. The event led to a temporary
loss of pager service to 45 million customers.
Activity in the two known Van Allen radiation belts grew so
intense
in May 1998 that a new belt was created, said Baker. The activity
was
detected by several NASA spacecraft, including NASA's WIND,
SAMPEX
and Polar satellites, all part of the multi-agency International
Solar and Terrestrial Physics Program.
"We have gotten a much clearer picture of cosmic particle
acceleration in the Van Allen Belts from these satellites,"
said
Baker, an investigator on the Polar and WIND experiments.
"New
observations indicate very rapid changes in these belts on
timescales
of months, weeks, days, hours and even seconds."
The new findings that killer electrons can be accelerated inside
the
Van Allen belts may help scientists better protect satellites by
powering them down or using back-up systems during electronic
storms.
"This knowledge will help us better prepare for the next
solar
maximum period when the sun is most active, expected in late 2000
or
early 2001," said Baker.
Scientists plan to coordinate observations from more than a dozen
spacecraft, which may allow them to produce "space
weather" maps of
particle acceleration that could be potentially damaging to
satellites. "In many ways, every spacecraft will act as a
high-energy
detector," said Baker.
In addition, CU-Boulder recently was selected to design, build,
operate and control a NASA satellite that will study the response
of
Earth's Van Allen radiation belts to the powerful solar wind. The
$12.8 million satellite project, known as the Inner Magnetosphere
Explorer, or IMEX, is being directed by Professor John Wygant of
the
University of Minnesota in Minneapolis.
Co-Investigators include Baker and LASP Associate Researcher
Xinlin
Li. CU-Boulder is expected to receive about half of the funding
for
the project.
IMEX will study the energetic charged particles -- primarily
protons
and electrons -- comprising Earth's radiation zones. In 1996,
Baker's
research indicated the operational failure of a Canadian
communications satellite, Anik E1, appeared to be linked to
severe
space weather.
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*
ON PAUL DAVIES AND THE ORIGIN OF LIFE
From Andrew Glikson <andrew.glikson@anu.edu.au>
Paul Davies is to be commended on his venture into biogenesis,
which I
find as inspiring as his earlier ideas on fundamental theological
and
philosophical questions. Metaphorically, Davies'
inter-disciplinary
cross-fertilisation from physics into the humanities and
geological
science is potentially as important for the discovery of the
"truth" -
whatever it is - as the proposed Mars-Earth cross-fertilisation
may have
had for the seeding of life.
As Paul Davies knows, the distinction between the scientific
method on
the one hand and religion and philosophy on the other hand is
that
scientific theories are only as good as are their testable
predictions -
i.e. whether they satisfy the principle of falsification. Short
of mere
speculation, the value of hypotheses such as Mars-Earth
bio-transport
and panspermia will reside in the development of diagnostic
criteria and
the design of discriminative tests. In the following I like
to comment
on some of the latter:
1. As identified by Zhao and Bada (1989; Nature, 339:463-464),
amino
isobutaric acid (CH3)2CNH2COOH) and racemic isovaline
(CH3CH2(CH3)CNH2COOH), which are exceedingly rare on Earth, form
major
amino acids in carbonaceous chondrites. Significantly these have
been
identified along the Cretaceous-Tertiary impact boundary at
Stevns
Klint, Denmark. Further tests of organic matter preserved in the
geologic record, for example in Precambrian carbonaceous shales
and
cherts, are critical for the testing of hypotheses such as
panspermia
and interplanetary bio-exchange.
2. I am unaware of unequivocal proof that isotopically light
12/13
Carbon is exclusively diagnostic of biogenetic activity, nor
whether the
carbon inclusions in apatite from rocks of the Akilia island,
southwest
Greenland, are 3.85 billion years old - an age recently disputed
by S.
Moorbath (Oxford) and colleagues. The oldest life forms
identified to
date are represented by 3.5 billion years old stromatolites and
associated bacteria in the Pilbara, Western Australia, and in the
Barberton Mountain Land, Transvaal. It is thus still possible
that the
onset of life had to wait until favourable conditions ensued in
terms of
the abatement of the incidence of cosmic and ultraviolet
radiation on
the early Earth.
3. Without doubt impact by asteroids and comets played a major
role in
the extinction/radiation history of life on Earth. However, I am
unaware
of data at hand requiring inter-planetary bacterial seeding. A
large
number of meteorites have been examined without identification of
bacterial spores. The occurrence of polycyclic aromatic
hydrocarbons
(PAHs) and carbonates showing fossil-like textures in the Martian
meteorite ALH84001 is not considered to provide evidence for
biological
processes (cf. Greshake, 1998, Lunar Planet. Sci. 29:1263).
4. Advanced experimental studies are required in order to define
the
upper limits on the resistance of DNA molecules in bacterial
spores to
external factors to which they are exposed underground and in
space,
i.e. in terms of temperature, pressure and radiation effects. The
problem of terrestrial bacterial contamination of
extra-terrestrial
samples and underground samples is severe. The more resistant DNA
may
prove to be under extreme conditions, the more likely it would be
that
life developed independently in millions/billions of locations in
the
universe, as suggested by Sagan and Shklovskii in their extensive
study
on Intelligent Life in the Universe (1977).
In conclusion, in so far as the scientific method legitimately
requires
both (1) tests based on theoretical speculation, and (2)
questions
arising from the data, I have yet to see data supporting
cross-planetary
fertilisation. Yet I accept it that - in the words of Carl
Sagan -
"absence of evidence is not evidence of absence".
On a reflective note, bearing in mind Paul Davies' philosophical
disposition, the question needs to be addressed regarding the
factors
underlying the ideological motivation for the modern space
culture,
namely the extent to which it arises as a "cargo
mentality" (e.g. mining
of asteroids and importation of mineral riches etc.), and/or
despair
vis-a-vis Earth's severe environmental predicament, and/or the
god-like
megalomania of some for universal conquest - the modern
equivalent of
the story of Babel's tower. Recognising the destructiveness
of our
species, it is to be hoped that, should Homo sapiens ever reach a
new
site of life in space, the locals will fare better than the
American
Indian, the Incas or the Aztecs ... It has been said that - if
there is
one thing space exploration has shown so far - it is that there
is no
second Earth in the solar system.
I congratulate Paul Davies on the Fifth Miracle.
Andrew Glikson
Australian National University
Canberra, A.C.T. 0200
andrew.glikson@anu.edu.au
11 December, 1998