A massive particle detector located a mile underground has found bits of antimatter known as geo-neutrinos deep inside the Earth. The find proves the Earth derives most of its power from radioactivity and could help us predict volcanoes and earthquakes.
Geo-neutrinos are antimatter particles created by the radioactive decay of uranium, thorium, and potassium deep within the Earth's crust and mantle. Although geo-neutrinos had first been found in 2005, this is the first real confirmation that they originate in large quantities deep underground. The successful detection using what amounts to a geo-neutrino "telescope" also means geologists have gained a powerful new tool to examine what the Earth's interior looks like.
The presence of these particles confirms radioactivity is a significant source of the Earth's internal power. It's long been thought that the decay of uranium and thorium heats up the Earth and contributes to convection processes in the mantle, in which rock flows steadily upwards, carrying extreme heat with it. This then powers plate tectonics, which is the primary force behind volcanic eruptions and earthquakes. Geo-neutrinos have now tipped the scale towards radioactivity as quite possibly the single biggest source of geothermal energy.
So what are these particles? Their matter counterparts, the neutrinos, are chargeless and inert elementary particles that are emitted by the Sun and cosmic rays. They have almost no mass at all and can pass through matter leaving barely any disturbance at all. This all combines to make neutrinos incredibly difficult to detect, and scientists have to go to extraordinary lengths to find them. This particular detector is located a mile underneath Italy's Gran Sasso Mountain, a necessary step to put as much thick rock as possible between the device and surface radiation that might interfere with neutrino detection.
But that's nothing compared to the detector itself. It's a massive nylon sphere containing 1,000 tons of hydrocarbon fluid. Around the sphere is a huge array of ultra-sensitive photodetectors that can hopefully spot the neutrinos passing through. And all of that is encased in a stainless steel sphere that in turn is suspended in 2,400 tons of purified water inside yet another steel sphere 59 feet in diameter. The device was originally built just to detect solar neutrinos, but the team soon realized they could also put it to use hunting for geo-neutrinos. Geo-neutrinos are thousands of times less common than their solar neutrino counterparts, and the detector only finds a few such particles per year.
The most exciting practical application of the discovery of geo-neutrinos is the creation of a worldwide network that can sense the particles at various locations. This data could then be used to figure out what's going on inside the Earth in a larger sense, and with sufficient precision it would be possible to predict when volcanoes were going to erupt or when earthquakes were going to occur. This would provide humanity an early warning system that it still sorely needs.
[via Physics Letters B]