Magazine article Science News

Glints from Inner Space: Sensing Earth's Hidden Radioactivity

Magazine article Science News

Glints from Inner Space: Sensing Earth's Hidden Radioactivity

Article excerpt

By recording faint blue-green twinklings in a huge subterranean detector, physicists have observed signatures of radioactivity deep within Earth. The new data enable the scientists to directly measure planet-wide quantities of the elements thorium and uranium, whose radioactive disintegrations generate about half of the planet's heat, according to previous estimates.

The power from those nuclear decays--which exceeds that of 10,000 nuclear power plants--propels many dynamic features of the planet, including crustal motions that give rise to earthquakes and volcanoes and the convection of softened rock within the planet's mantle.

Before the new measurements, "there were only guesses" about radioactivity's contribution to Earth's internal heat, says Giorgio Gratta of Stanford University, a leader of the experiment. He, coleader Atsuto Suzuki of Tohoku University in Sendai, Japan, and their colleagues spent more than 2 years looking for telltale flickers in the Kamioka Liquid Scintillator Antineutrino Detector (KamLAND)--a tough, transparent balloon filled with 1,000 tons of baby oil, benzene, and fluorescent chemicals. Suspended 1 kilometer underground near Toyama, Japan, the balloon is surrounded by more than 1,800 supersensitive light detectors.

When they show themselves, the elusive flickers signal arrivals of subatomic anti-matter particles called antineutrinos. Droves of those particles and their ordinary-matter counterparts, neutrinos, are left over from the Big Bang. They're also produced in nuclear reactions in stars and in commercial power plants and when cosmic rays hit atmospheric atoms.

Nuclear decays of thorium, uranium, and the isotopes into which those elements transform give off antineutrinos. The majority of these escape Earth unscathed. Occasionally, however, an antineutrino from an underground decay collides with a molecule in the KamLAND tank, resulting in a signature written in light: two flashes in rapid succession. …

Search by... Author
Show... All Results Primary Sources Peer-reviewed

Oops!

An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.