geoneurtrinos - new "landmark" discovery

ELUSIVE PARTICLE FOUND
Antineutrinos may help scientists learn chemistry of Earth's interior
San Francisco Chronicle, July 28, 2005

It is the first clear identification of radioactive chemical elements in the Earth's deep interior, and it also enables scientists to understand how they contribute to the Earth's continuous output of heat, he said.

To conduct their work, the scientists used a uniquely powerful particle detector buried beneath a Japanese mountain -- and they are calling the particles they have caught "geoneutrinos."

In the same issue of Nature, William F. McDonough, a noted University of Maryland geologist, hailed the "landmark result."
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The KamLAND instrument has also detected huge quantities of antineutrinos from the sun and from cosmic rays. The source of the geoneutrinos, however, is the uranium and thorium that lie deep within Earth's mantle. Because almost all the particles pass unimpeded through the Earth and on into space, the detector has picked them up at a rate of only one a month.

Even that infrequent detection, however, is enough to provide evidence that uranium and thorium are indeed abundant in the Earth's deepest regions, Gratta said.

Gratta said about half of the Earth's heat represents the primordial temperature that remains as the planet slowly cools from the heat of its formation some 4.5 billion years ago. But the rest must come mostly from the radioactivity of Earth's interior rocks, and this can be measured by measuring the energy spectrum of the antineutrinos, he said.
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Norman Sleep, a Stanford geophysicist who was not involved in the Japanese experiment, called the result "an achievement that will have major implications for understanding how the Earth and planets formed, how continents move by plate tectonics and what drives formation of the mid-ocean ridges. With more and bigger detectors, we should learn much more about the chemistry of the earth's interior."

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