Results from KamLAND, an underground neutrino detector in central Japan, show that anti-electron neutrinos emanating from the earth, so-called geoneutrinos, can be used as a unique window into the interior of our planet, revealing information that is hidden from other probes.

Surprising as it may seem, for all that we have learned about far distant astrophysical events like deep-space supernovae, dark energy, or even the Big Bang itself, the interior of our own planet remains a mysterious and largely unexplored frontier. Among the many questions is the source of terrestrial heat. The total amount of heat given off by the earth at any given moment has most recently been estimated at about 31 terawatts (TW). A terawatt is equivalent to one trillion watts. For comparison, the average energy consumption of the United States at any given moment is 0.3 trillion watts.

Much of this heat is re-radiated energy from the sun, but nearly half is produced from the earth’s interior. Radioactivity is known to account for some of this heat, but exactly how much has been difficult to say because, until now, there has been no accurate means of measuring radiogenic heat production.These latest experimental results from KamLAND indicate that is no longer the case.

“Our results show that measuring the flux of Earth’s geoneutrinos could provide scientists with an assay of our planet's total amount of radioactivity,” said Stuart Freedman. “Measuring geoneutrinos could also serve as a deep probe for studying portions of the planet that are otherwise inaccessible to us.”

Said Stanford’s Gratta, “There are still lots of theories about what’s really inside the earth and so it’s still very much an open issue. The neutrinos are a second tool, so we’re doubling the number of tools suddenly that we have, going from using only seismic waves to the point where we’re doing essentially simple-minded chemical analysis.”

Added physics Professor Atsuto Suzuki, director of the Research Center for Neutrino Science, vice president of Tohoku University and spokesperson for the Japanese team at KamLAND, “We now have a diagnostic tool for the Earth`s interior in our hands. For the first time we can say that neutrinos have a practical interest in other fields of science.” Dennis Kovar, Associate Director for Nuclear Physics of DOE’s Office of Science, agreed with Suzuki. "I believe the results of the multinational KamLAND collaboration are very interesting and indicate that science has a new, powerful tool for peering deep into the core of our planet."

In measuring geoneutrinos generated in the decay of natural radioactive elements in the earth's interior, scientists believe it should be possible to get a three-dimensional picture of the earth's composition and shell structure. This could provide answers to such as questions as how much terrestrial heat comes from radioactive decays, and how much is a "primordial" remnant from the birth of our planet. It might also help identify the source of Earth’s magnetic field, and what drives the geodynamo. >from *First Measurement of Geoneutrinos at KamLAND* July 27, 2005

related context
> what are neutrinos telling us?. april 22, 2005.
> quantum universe: the revolution in 21st-century physics. june 11, 2004
> working neutrino telescope: a novel way of seeing universe. may 22, 2001
> first direct evidence for tau neutrino. july 21, 2000

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