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Abstract
The cosmic dust concentration in the solar
system during the last ice age was investigated by means of eight
samples from taken from a depth of 1215-1279 m in the Camp Century
ice core (77°10'N, 61°08'W). Dust filtered from
these samples was analyzed for the presence of the cosmic dust
indicators iridium and nickel using the neutron activation analysis
technique. This study was carried out to test the hypothesis
that the climatic change toward the end of the Last Ice Age was
triggered by an incursion of nebular material into the Solar
System. The analytical results are consistent with this hypothesis.
Concentrations of Ir and Ni in the ice were one to two
orders of magnitude higher during the latter portion of the Last
Ice Age (19,700 - 14,200 years BP)* as compared with current
levels. Ir and Ni levels in 6 out of 8 samples suggest a total
cosmic dust influx rate of about 0.5 - 3 X 10^7 tons/yr to the
Earth's surface as compared with about 1 - 7 X 10^5 tons/yr for
the current influx. Elemental concentrations in 6 of the
8 dust samples range from 6 - 96 ppb for Ir and <60 to 3200
ppm for Ni. It is concluded that a major fraction of this
invading dust would have been of submicron size in which case
the concentration of light scattering particles would have been
sufficient to significantly alter the light transmission properties
of the Solar System and substantially affect the Earth's climate.
These results mark the first time that cosmic dust deposition
rates have been estimated for prehistoric times using the polar
ice record.
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