Saturday, April 27, 2013

Earth's core temperature hotter than previously thought

Earth's core temperature hotter than previously thought, On Friday, a study on the melting of iron in Earth's core based on fast X-ray diffraction was published by Science Magazine. The study estimates that the temperature of Earth's core is 6230±500 K. Earlier estimates were lower, at about 5300 K. For reference, the effective temperature of the atmosphere of the Sun is 5778 K.

In the experiment, researchers used a diamond anvil cell to pressurize a sample of iron to 200 GPa (about 2 million times the atmospheric pressure at Earth's surface) and then heated it with a high intensity laser to simulate the conditions at the inner core boundary. As the iron changed phase from solid to liquid, X-ray diffraction was performed at the European Synchrotron Radiation Facility. As iron atoms alter states, X-rays diffract at different angles, which can be measured to give researchers an estimate of the temperature of the atoms. The results were then extrapolated mathematically to the estimated 330 GPa pressure at the inner core boundary.

The earlier figure of 5300 K was obtained by similar experiments performed in the early 1990s, which used less advanced methods of measuring the X-rays.

"Other people made other measurements and calculations with computers and nothing was in agreement. It was not good for our field that we didn’t agree with each other," said Dr. Agnes Dewaele, who co-authored the research piece in Science, in an interview with BBC News. "Now everything agrees."

The new measurement is important because it provides the necessary data to understand the generation of Earth's magnetic field. The process that generates the magnetic field requires a temperature differential of 1500 K between the mantle and the inner core, and this requirement is now confirmed to be met. The old temperature figure was not hot enough to explain the process.

The new research is beneficial to all fields which study aspects of the planet’s interior. "We have to give answers to geophysicists, seismologists, geodynamicists - they need some data to feed their computer models," Dr. Dewaele said.

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