[meteorite-list] Cosmic Dust in Terrestrial Ice

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Sat Aug 5 15:46:15 2006
Message-ID: <001801c6b8c7$cbb5f4a0$2a7f4b44_at_ATARIENGINE>

Hi,

    This is one of those odd cases of knowledge being acquired
and lost and re-acquired in generational cycles, even in the so-called
"exact" sciences. The authors of this study say:
>
> The ratio of 4He in terrestrial dust to the dust concentration itself
> reveals a marked difference between the last Ice Age and the current
> warm period. As . Gisela Winckler, head of the working group "Isotope
> Tracers and Constant Flux Proxies" at L-DEO says, "the terrestrial dust
> coming down on Antarctica during the Ice Age obviously is not the same
> as that during warm periods. This may be due to the mineral dust
> originating from different regional sources or to changes in weathering,
> the process responsible for production of dust." Both scientists now
> want to intensify their collaboration even further and investigate the
> details of this phenomenon.
>
    Just as there are those who decry impact explanations because
they are a form of "catastrophism," there was great resistance in the
mid-nineteenth century to the proposal that there had been "ice ages,"
dismissing the evidence because the whole idea was forbidden as
"catastrophism."
    When we got over that, we learned a lot about ice ages, and one
of the paradoxes of ice ages is that they are times of global dessication
and dryness. Most of the great deserts were formed during ice ages.
At the peak of the last ice age, the sea level was 450 feet lower than
today.
    I live at 613 feet above sea level and 1200 miles inland, but
storms have no difficulty bringing Gulf moisture over 1200 miles
of mostly flat land and dumping 40-odd inches of rain per year
on me. But if I were suddenly at 1063 feet above sea level and the
ocean was either hundreds of miles further away or at the foot of
a 400 foot cliff, I would get a lot less rain. To complicate the
problem, the temperature would be 10-15 degrees cooler; there
would be fewer rain storms and they would carry less water.
Southern Illinois would look a lot like eastern Colorado. Water
erosion would cease to be common; wind erosion would take
its place. The Dust Bowl of the Depression is a very weak
rehearsal of this effect. These effects would be world-wide;
I just used a local example.
    The authors of the study say dust came from different regions
and from different weathering mechanisms and these changes need
to be investigated. There are mountains of studies 1880-1930 that
document these changes in great detail; they're sitting in geological
libraries and have never been put on the internet; go take a look.
An example of "knowledge being acquired and lost and re-acquired
in generational cycles..."
    I ran across a reference the other day on a NASA website to
satellite studies "discovering" that the Sahara has underground
rivers in a vast connected web. Nope, not "discovered," not by
a long shot. Forty years (1890-1930) of difficult field work by
(mostly) French geologists discovered, traced, mapped, and
documented, in exquisite detail, not only the network of those
underground "rivers" in the Sahara but identified and mapped
their original surface watercourses. Yeah, satellites can probably
do a great deal to expand that knowledge and they should, but
field work in the Sahara is no picnic and if you do it, you should
get credit for it...
    The Sahara, by the way, is not an "ice age" desert, but a modern
one. During the "recent" ice ages, it was wet, temperate, forested,
a paradise of game and good times for a substantial early human
population. The striking contrast between that picture and the
"Great Sand Sea" of today is a perfect example of what a huge
change a shift in weather and weathering can accomplish in a
relatively short time.
    The current "southward march" of the sand is not a climatic
effect, but a physical one. Sand is generated continually in the
central Sahara and like any sandpile to which more sand is
added centrally, it spreads by gravity in any direction the slope
allows, in this case southward.
    The Sahara is only an example of the complexity of ice age
desert change (in reverse). There are lots of geologists on this
List and they all know about "loess." There are parts of the world
where this wind-deposited fine soil (commonly called "dust")
is hundreds of feet deep (NW China, the Great Plains). These
are the soils rapidly emplaced in a cold, dry and dusty ice age
world.
    Perhaps isotope studies can refine our knowledge of the
mechanisms of what an ice age world was like and what the
precise role of differing mechansisms of weathering were. By
all means, they should "investigate the details of this phenomenon,"
but this is not a "discovery," just really good work, of which
a lot has already been done.
    And, for Rob Matson, I just want to point out, an ice age is
what happenes when you



----- Original Message -----
From: "Ron Baalke" <baalke_at_zagami.jpl.nasa.gov>
To: "Meteorite Mailing List" <meteorite-list_at_meteoritecentral.com>
Sent: Friday, July 28, 2006 12:26 PM
Subject: [meteorite-list] Cosmic Dust in Terrestrial Ice


>
> http://www.awi-bremerhaven.de/AWI/Presse/PM/pm06-2.hj/060728Cosmic%20dust-e.html
>
> Cosmic Dust in Terrestrial Ice
> Alfred-Wegener-Institute
> July 28, 2006
>
> For the last 30,000 years, our planet has been hit by a constant rain of
> cosmic dust particles. Two scientists from the Lamont-Doherty Earth
> Observatory (LDEO) at Columbia University in New York and the
> Alfred-Wegener-Institut (AWI) for Polar and Marine Research in
> Bremerhaven, Germany, have reached this conclusion after investigating
> the amount of the helium isotope 3He in cosmic dust particles preserved
> in an Antarctic ice core over the last 30,000 years. They have shown
> that this rare helium isotope in cosmic dust exceeds that of terrestrial
> dust in ice by a factor of 5,000. Moreover, measurements of the amount
> of 4He - a helium isotope much more common on Earth - in the Antarctic
> ice strongly suggest a change of origins in terrestrial dust between the
> last Ice Age and the interglacial warm period we currently live in.
>
> In the current issue of Science, the scientists from New York and
> Bremerhaven for the first time present chronologically resolved
> measurements of the 3He and 4He flux of interplanetary and terrestrial
> dust particles preserved in the snow of the Antarctic. According to
> current estimates, about 40,000 tons of extraterrestrial matter hit the
> Earth every year. "During its journey through interplanetary space, the
> cosmic dust is charged with helium atoms by the solar wind. At his point
> they are highly enriched with the rare helium isotope 3He," explains Dr
> Hubertus Fischer, head of the research program "New keys to polar
> climate archives" at the Alfred Wegener Institute. "Cosmic dust
> particles in the size of a few micrometers enter the Earth's atmosphere
> unharmed and carry their helium load unchanged to the Earth's surface
> where they are, among other places, preserved in the snow and ice of the
> polar ice caps." Due to the high temporal resolution uniquely to be
> found in ice cores, it has now been possible for the first time to
> determine the temporal variability of this helium flux between glacial
> and interglacial periods along with the 3He and 4He ratios of these
> exotic particles. The results are expected to have significant impact on
> interpretation of high-resolution climate archives, such as ice, marine
> and lake sediment cores.
>
> This, however, is not all the helium isotope method has to offer. The
> ratio of 4He in terrestrial dust to the dust concentration itself
> reveals a marked difference between the last Ice Age and the current
> warm period. As . Gisela Winckler, head of the working group "Isotope
> Tracers and Constant Flux Proxies" at L-DEO says, "the terrestrial dust
> coming down on Antarctica during the Ice Age obviously is not the same
> as that during warm periods. This may be due to the mineral dust
> originating from different regional sources or to changes in weathering,
> the process responsible for production of dust." Both scientists now
> want to intensify their collaboration even further and investigate the
> details of this phenomenon.
>
> EPICA
> Data for this study have been collected within the European Project for
> Ice Coring in Antarctica (EPICA). As the German partner within EPICA,
> Alfred Wegener Institute is responsible for the Dronning Maud Land
> drilling operations. The EPICA project is carried out by a consortium of
> ten European countries (Belgium, Denmark, France, Germany, UK, Italy,
> the Netherlands, Norway, Sweden and Switzerland). Coordinated under the
> roof of the European Science Foundation (ESF), EPICA is funded by the
> participating countries and the European Union.
> The manuscript "30,000 Years of Cosmic Dust in Antarctic Ice" will be
> published in Science on July 28, 2006.
>
> Bremerhaven, July 27, 2006
>
> In case of publication, please provide a copy.
>
> Your contact person at Alfred Wegener Institue is Dr Hubertus Fischer
> (0471-4831 1174; email hufischer_at_awi-bremerhaven.de) and in the public
> relations department. Dr Angelika Dummermuth (0471-4831 1742; email
> medien_at_awi-bremerhaven.de). For further information from LDEO, please
> contact Dr Gisela Winckler (++1-845-365 8756 or
> winckler_at_ldeo.columbia.edu) and for media contact: Mary Tobin (Tel.
> ++1-212-854 9485; email: mtobin_at_ei.columbia.edu) or Ken Kostel (Tel.
> ++1-212-854 9729; email: kkostel_at_ei.columbia.edu). Printable images can
> be found on our webpage at
> http://www.awi-bremerhaven.de/AWI/Presse/PM/index-d.html.
>
> Lamont-Doherty Earth Observatory (L-DEO), member of the Earth Institute
> at Columbia University, is one of the world's leading research centres
> examining the planet from its core to its atmosphere, across every
> continent and every ocean. From global climate change to earthquakes,
> volcanoes, environmental hazards and beyond, Observatory scientists
> provide the basic knowledge of Earth systems needed to inform the future
> health and habitability of our planet.
>
>
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Received on Sat 05 Aug 2006 03:46:07 PM PDT