Geologists have long known that Earth’s core, some 2,900 kilometers beneath our feet, is a dense, chemically laden ball of iron roughly the size of Mars. Pressures there bear down with the weight of 3.5 million atmospheres, and temperatures reach 5,538 degrees Celsius – as hot as the surface of the Sun. It’s a place where iron is a fluid and a solid, and it spirals like liquid confetti.
The heat of Earth’s inner core helps animate the tectonic plates above it, to build up mountains and gouge out seabeds. At the same time, the jostling of core iron generates Earth’s magnetic field, which blocks dangerous cosmic radiation.
But reporting recently in the journal Nature, Dario Alfe of University College London and his colleagues presented evidence that iron in the outer layers of the core is wasting heat through conduction at two to three times the rate of previous estimates.
The theoretical consequences are far-reaching. The scientists say something else must account for the missing thermal energy in their calculations. They offer these possibilities:
The core holds more radioactive material, like potassium or thorium, than anyone had suspected, and its decay is giving off heat.
The iron of the innermost core is solidifying at a startlingly fast clip and releasing the latent heat of crystallization in the process.
The chemical interactions among the iron alloys of the core and the rocky silicates of the mantle are much fiercer and more energetic than previously believed.
“People are excited” by the report, Dr. Alfe said. “They see there might be a new mechanism going on.”