By Sid Perkins
Laboratory experiments investigating the crystal structure of iron-silicon alloys at hellish temperatures and pressures may yield new insights into the mineral composition of Earth’s solid, inner core, scientists say.
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Iron is by far the most abundant chemical element at the center of the planet. The travel times of seismic waves passing through Earth’s liquid outer core–the only probe that scientists can use to survey that deep below Earth’s surface–suggest that material there is only about 90 percent as dense as pure iron would be at those pressures and temperatures. The lower density must result from a smattering of lighter elements such as carbon, oxygen, sulfur, or silicon, says Dion L. Heinz, a geophysicist at the University of Chicago.