Antineutrinos Open Window to Earth's Interior

GEOCHEMISTRY

A major international collaboration has recorded, for the first time, the tracks of antineutrinos—extremely light antimatter particles—that are produced during the decay of radioactive elements such as thorium and uranium in Earth’s interior (Nature 2005, 436, 499).

Scientists believe that part of the heat emanating from Earth’s core comes from the decay of such radioactive elements, but studying the chemical makeup of our planet’s interior has thus far been limited to making inferences from seismic oscillations and the chemical analysis of meteorites and shallow rocks. The new results, obtained using Japan's underground Kamioka liquid scintillator antineutrino detector (KamLAND), suggest that scientists will soon be able to study radioactive elements inside Earth more directly.

Neutrinos interact only occasionally with other particles and so are very difficult to detect. The rate at which the so-called geoneutrinos were spotted by KamLAND—about one per month—as well as their energies, suggest that amounts of uranium and thorium in Earth's interior match the amounts predicted by the seismicity and meteorite studies. In a commentary, Nature praises the “first detection of geoneutrinos from beneath our feet” as “a landmark result. It will allow better estimation of the abundances and distributions of radioactive elements in the Earth, and of the Earth’s overall heat budget.”