PLEASE NOTE:
*
Date sent: Mon, 14 Jul 1997 11:25:36 -0400 (EDT)
From: HUMBPEIS <B.J.PEISER@livjm.ac.uk>
Subject: Purdue Report on Meteorite Streams
To: cambridge-conference@livjm.ac.uk
Priority: NORMAL
from: Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
Purdue University
CONTACT: Lipschutz, (765) 494-5326; e-mail,
rnapuml@vm.cc.purdue.edu
Compiled by Amanda Siegfried, (765) 494-4709; e-mail,
amanda_siegfried@uns.purdue.edu
Purdue News Service: (765) 494-2096; e-mail,
purduenews@uns.purdue.edu
June 1997
Report puts meteorite streams into mainstream science
WEST LAFAYETTE, Ind. -- The road map for our solar system may be
sprinkled with streams of meteoroids, says a Purdue University
professor.
Michael Lipschutz, professor of chemistry who headed the team
that
discovered the first evidence for a meteoroid stream in 1993, has
found a second stream by analyzing a series of meteorites that
have
crashed to Earth between 1812 and 1992.
"This new stream appears to have deposited meteorites on
Earth over
two different intervals," Lipschutz says. "Apparently,
the Earth
intersected the stream's orbit at these points in time, and some
of
the meteoroids that were traveling in the stream landed on
Earth."
He reported his findings in the April issue of the Journal of
Geophysical Research-Planets.
Meteorites are the fragments of small objects called meteoroids
that
survive passage through the atmosphere and fall on the Earth's
surface. Theoretically, a meteoroid stream is made up of a group
of
rocky fragments that are derived from the breakup of a near-Earth
object and then travel in space in the same general orbit,
Lipschutz
says.
"Meteoroids traveling together would likely represent
fragments of
the same asteroid, thus they would have a similar chemical
makeup,"
he says.
Using this knowledge, Lipschutz was able to link 17 meteorites
that
fell to Earth in two separate arrays by analyzing the trace
elements
in the meteorites. Trace elements are chemical markers that are
found in very tiny amounts, such as parts per million or parts
per
billion.
He then compared the contents of the samples with a set of 33
meteorites of similar composition that fell to Earth at random
between 1773 and 1970. The 17 meteorites proved to have a
chemical
makeup that was similar to each other and significantly different
from the meteorites in the random falls.
"Only meteorites from a single source could account for
these
differences," Lipschutz says.
The 17 meteorites fell to Earth in over a period of time in two
separate arrays, indicating that the Earth may have intersected
two
different parts of the stream, Lipschutz says. The first group of
meteorites landed from 1812 through 1831, and a second group of
meteorites landed from 1843 and 1992. The falls all occurred
during
the months of September and October.
In addition, several samples from the stream have interesting
histories, Lipschutz says.
"The first meteorite fall, called Borodino, fell two days
before the
famous 1812 battle there, the ultimate result of which was the
devastating retreat of Napoleon's army from Russia," he
says,
"although no mention appears in history treatises of the
Napoleonic
era."
The most recent fall, which occurred on Oct. 9, 1992, in
Peekskill,
N.Y., hit a car and was observed and videotaped over a five-state
area, Lipschutz says.
The existence of meteoroid streams was first proposed by
Lipschutz
and colleagues in 1986 to explain chemical differences, such as
concentrations of trace elements, between Antarctic and
non-Antarctic meteorites.
*
Date sent: Mon, 14 Jul 1997 11:17:41 -0400 (EDT)
From: HUMBPEIS <B.J.PEISER@livjm.ac.uk>
Subject: Astronomical Theory Offers New Explanation For Ice Age
To: cambridge-conference@livjm.ac.uk
Priority: NORMAL
COSMIC DUST LOADING & ICE AGES
20 years after British astronomers such as Fred Hoyle, N
Wickramasinghe, Victor Clube and Bill Napier first suggested that
periodic ice ages might have been triggered by periodic
dustloadings
by cosmic debris and cometary microparticles, two American
researchers are now convinced to have found hard evidence for
such
an astronomical explanation. While the advocates of coherent
catastrophism think that intersections of the Earth with periodic
cometary streams are the main reasons for the cyclical nature of
ice
ages, the American scholars believe that a periodic change of the
location of Earth's orbit as such would inevitably lead to higher
accretion of cosmic dust and debris. If, however, massive cosmic
dust loads are able to trigger extreme and long lasting ice ages
on
Earth, much smaller dust loads migh also be responsible for
short-term climatic downturns which are detectable in the ice
core
and tree ring records of the Holocene period.
Benny J Peiser
----------------------------------------------------------------
from: Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
University of California at Berkeley
Astronomical theory offers new explanation for ice age
By Jeffery Kahn, LBNL
Berkeley, 7/11/97 -- Recent ice ages -- ten periods of glaciation
in
the past million years -- are caused by changes in the tilt of
the
Earth's orbit, according to research published in today's (July
11)
issue of Science magazine. The new analysis also presents strong
evidence that another long prevailing theory does not account for
these ice ages.
Researchers Richard A. Muller of the Ernest Orlando Lawrence
Berkeley National Laboratory (Berkeley Lab) and the University
of California at Berkeley, and Gordon J. MacDonald of the
International Institute for Applied Systems Analysis, Austria,
are co-authors of the Science article.
Muller and MacDonald report that cyclical changes in the location
of
the Earth's orbit cause differing quantities of extraterrestrial
debris to come into the Earth's atmosphere. This, in turn,
results
in variations of climate on the planet.
Said MacDonald, "As the Earth moves up and down in the plane
of the
solar system, it runs into various amounts of debris, dust and
meteoroids. Our work was an outgrowth of investigations of larger
impacts, such as the comet or asteroid that killed the dinosaurs.
However, meteoroids and dust are much smaller and more spread-out
over time."
Muller, a professor of physics at UC Berkeley, notes that this
new
research has important implications for the understanding of the
present climate, and for predictions of future climate.
"As far as we know," he said, "none of the present
climate models
include the effects of dust and meteors. And yet our data
suggests
that such accretion played the dominant role in the climate for
the
last million years. If we wish to make accurate predictions, we
must
understand the role played by such material."
Despite the current relatively warm climate on Earth, regular
recurring epochs of glaciation have dominated the planet for the
past million years. Ten times, glaciers have advanced and then
retreated with the duration of retreat (and corresponding warmth)
frequently lasting not more than 10,000 years. The Earth has been
in
a warm period for about 10,000 years now.
In the paper in Science, the researchers compared the geological
record to the climactic cycles that would result from their
theory
and to that of the competing theory, first published in 1912 by
Serbian scientist Milutin Milankovitch. Using a geological
fingerprinting technique, Muller and MacDonald found that the
climactic changes recorded in the rocks matched their theory but
not
that of Milankovitch.
Milankovitch said the ice ages are caused by variations in
sunlight
hitting the continents. In his theory, the ice ages are linked to
"eccentricity," a very gradual, cyclic change in the
shape of the
Earth's egg-shaped orbit around the sun that completes a cycle
roughly every 100,000 years. Eccentricity changes the Earth's
average annual distance from the sun and slightly alters the
amount
of sunlight hitting the Earth.
To visualize the different astronomical cycle that Muller and
MacDonald have found to match that of the climatic record,
imagine a
flat plane with the sun in the center and nine planets circling
close to the plane. In fact, all the planets orbit the sun close
to
such a fixed orbital plane. The Earth's orbit slowly tilts out of
this plane and then returns. As Muller first calculated in 1993,
the
cycle of tilt repeats every 100,000 years.
In their Science paper, Muller and MacDonald examine the
geological
record of the past million years to see which of the two
100,000-year cycles (eccentricity or tilt) matched the data.
They applied a technique called spectral analysis to ocean
sediments
taken from eight locations around the world, examining the
oxygen-18
composition. This isotope is generally accepted to reflect the
percentage of the Earth's water frozen in ice.
Muller and MacDonald's analysis yields "spectral
fingerprints" which
can be compared to the predictions of the two theories. Their
analysis shows a clear pattern: The fingerprints of the ice ages
show a single dominant feature, a peak with a period of 100,000
years. This precisely matches their theory. The fingerprints do
not
match the expected trio of peaks predicted by the Milankovitch
theory.
Said Muller, "The mechanism proposed by Milankovitch could
be
adjusted to explain the cycles of glaciation that occurred prior
to one million years ago. However, for the past million years the
glacial record is an excellent match to the cycle of tilt."
Berkeley Lab conducts unclassified scientific research for the
U.S.
Department of Energy. It is located in Berkeley, California and
is
managed by the University of California.