(Image source: OurAmazingPlanet)

BY: STEVEN SPARKMAN

It’s a mystery that bothers planetary scientists. The planet we live on is dumping 44 terawatts of heat into space, but scientists aren’t sure where it’s all coming from. Now scientists in Japan say they’ve figured out about half of it.

International Business Times explains.

“We’re aware that heat drives our Earth -- from the planet’s core to its surface. Heat enables Earth’s magnetic field, spreads the seafloor and keeps continents on the move. … But where does this heat come from? According to recent research, radioactive decay supplies only about half the Earth’s heat, while primordial heat -- leftover from the planet’s formation -- accounts for the rest.”

The discovery means the Earth is still cooling down from its volatile birth -- 4.5 billion years ago. But how did the scientists at Japan’s KamLAND detector measure radiation in the center of the Earth? By looking for extremely rare particles in a vat of oil.

“The KamLAND detector is a huge balloon filled with 1000 tonnes of mineral oil … Very occasionally an antineutrino will react with a proton in the oil … By looking for signals ... KamLAND can discriminate between extremely rare antineutrino events and the much more common signals due to background radiation.” (Source: physicsworld.com)

Antineutrinos come from certain radioactive decays. If you know how often those decays happen, and how rare it is for the particles to interact, you can calculate how much energy is being produced. So they watched their vat of mineral oil and saw around 100 antineutrinos -- over seven years.

“Despite the small number, the team estimates that about 4.3 million of the particles generated by the radioactive decay of uranium-238 and thorium-232 pass through each square centimeter of Earth's surface each second. The heat continuously generated by all that radioactivity is about 20 terawatts...” (Source: ScienceNOW)

While scientists think leftover heat from the planet’s formation makes up the rest, they can’t really be sure. There could be entirely unknown processes to be discovered in Earth’s core. But a writer for Scientific American says we shouldn’t let the processes we do know about go to waste.

“...with fission still pumping out so much heat, Earth is unlikely to cool ... for hundreds of millions of years thanks to the long half-lives of some of these elements. And that means there's a lot of geothermal energy -- or natural nuclear energy -- to be harvested." 

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Transcript by Newsy.