Core chemistry

Physicists at an underground observatory in Japan have for the first time detected and analyzed antineutrinos 8212; elusive particles 500,0...

Physicists at an underground observatory in Japan have for the first time detected and analyzed antineutrinos 8212; elusive particles 500,000 times smaller than an electron 8212; created by radioactive fires deep within the Earth.

The observation sheds new light on the complicated processes that generate heat below the Earth8217;s crust and generate the movement of tectonic plates.

The findings are 8220;a landmark result that 8230; will allow better estimation of the abundance and distributions of radioactive elements in the earth,8221; wrote University of Maryland geologist William G. McDonough in an editorial accompanying the report in Nature.

An 85-member team led by physicists Giorgio Gratta at Stanford and Atsuto Suzuki at Japan8217;s Tohoku University snared the tiny subatomic particles with the help of the Kamland observatory, which is essentially a giant vat of baby oil, benzene and fluorescent material that flashes when an antineutrino pass through it.

The detector is buried in a cavern underneath a mountain in Kamioka, Japan, to reduce 8220;pollution8221; from nuclear reactors, which also can generate antineutrinos. Physicists were able to distinguish between the two tiny particles because antineutrinos from nuclear reactors have a different energy spectrum.

8220;What may be most revolutionary is the alternative it provides to traditional probing methods, which simply bore down from the surface 8212; a very costly technique that can trigger earthquakes,8221; said Stanford geophysicist professor Norman Sleep. The deepest borehole drilled to date is about 7.4 miles deep, reaching to 1/500 of the Earth8217;s radius.

The new technique 8220;promises to give geologists and seismologists better data to predict volcanoes, earthquakes and other volatile Earth dynamics,8221; Sleep said.

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Gratta said the Kamland results, particularly the ratios of thorium to uranium it discovered, 8220;support earlier theories about the nature of matter in the Earth8217;s crust, core and lower mantle.8221;

The team concluded that about 16.2 million antineutrinos per square centimeter per second are streaming out of the interior. They calculated that radioactive decay producing that level of radiation is likely generating about 24 terawatts of heat continuously.

That is about the same amount of heat as is generated by chemical reactions and phase changes, such as crystallization of liquids, and heat left over from the Earth8217;s formation.

8220;Antineutrinos reveal just some basic chemistry about the inner Earth. But when you know nothing, knowing a little can make a big difference,8221; Gratta said.

LAT-WP