The amount of nuclear fuel and radioactive power remaining inside the Earth may be calculated by 2025, which can help estimate how long this fuel will last, scientists say.
Earth requires fuel to drive plate tectonics, volcanoes and its magnetic field. Like a hybrid car, Earth taps two sources of energy to run its engine: primordial energy from assembling the planet and nuclear energy from the heat produced during natural radioactive decay.
Scientists have developed numerous models to predict how much fuel remains inside Earth to drive its engines – and estimates vary widely – but the true amount remains unknown.
A team from the University of Maryland in the US, Charles University in Prague and the Chinese Academy of Geological Sciences, now claims it will be able to determine by 2025 how much nuclear fuel and radioactive power remain in the Earth’s tank.
To calculate the amount of fuel inside Earth by 2025, the researchers will rely on detecting some of the tiniest subatomic particles known to science – geoneutrinos.
These antineutrino particles are byproducts of nuclear reactions within stars (including our sun), supernovae, black holes and human-made nuclear reactors. They also result from radioactive decay processes deep within the Earth.
Detecting antineutrinos requires a huge detector the size of a small office building, housed about a mile underground to shield it from cosmic rays that could yield false positive results.
Inside the detector, scientists detect antineutrinos when they crash into a hydrogen atom. The collision produces two characteristic light flashes that unequivocally announce the event.
The number of events scientists detect relates directly to the number of atoms of uranium and thorium inside the Earth. The decay of these elements, along with potassium, fuels the vast majority of the heat in the Earth’s interior.
To date, detecting antineutrinos has been painfully slow, with scientists recording only about 16 events per year from the underground detectors KamLAND in Japan and Borexino in Italy.
However, researchers predict that three new detectors expected to come online by 2022 – the SNO+ detector in Canada and the Jinping and JUNO detectors in China – will add 520 more events per year to the data stream.
"Once we collect three years of antineutrino data from all five detectors, we are confident that we will have developed an accurate fuel gauge for the Earth and be able to calculate the amount of remaining fuel inside Earth," said William McDonough, a professor at the University of Maryland.
"Knowing exactly how much radioactive power there is in the Earth will tell us about Earth’s consumption rate in the past and its future fuel budget," said McDonough.
"By showing how fast the planet has cooled down since its birth, we can estimate how long this fuel will last," he said.
The research was published in the journal Nature Scientific Reports.