Newly discovered flux in the Earth may solve missing-mantle mystery

Research points to large reservoirs of material deep in the mantle that may help to explain Earth's origins. It's widely thought that the Earth arose from violent origins: Some 4.5 billion years ago, a maelstrom of gas and dust circled in a massive disc around the sun, gathering in rocky clumps to form asteroids. These asteroids, gaining momentum, whirled around a fledgling solar system, repeatedly smashing into each other to create larger bodies of rubble - the largest of which eventually cooled to form the planets. Countless theories, simulations and geologic observations support such a scenario. But there remains one lingering mystery: If the Earth arose from the collision of asteroids, its composition should resemble that of meteoroids, the small particles that break off from asteroids. But to date, scientists have found that, quite literally, something doesn't add up: Namely, the Earth's mantle - the layer between the planet's crust and core - is missing an amount of lead found in meteorites whose composition has been analyzed following impact with the Earth. Much of the Earth is composed of rocks with a high ratio of uranium to lead (uranium naturally decays to lead over time).