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Inside Mercury, Is It Snowing Iron?

Irene Klotz, Discovery News

The researchers determined that as Mercury's outer core cools, iron atoms condense into cubic flakes that sink toward the planet's center. As the iron sinks, the lighter, sulfur-rich liquid deep in the core rises upward, creating a convection current that powers the process and produces the planet's weak magnetic field.

"Our findings provide a new context into which forthcoming observational data from MESSENGER can be placed," said University of Illinois geology professor Jie Li, who co-authored on a paper about the research appearing in the April issue of Geophysical Research Letters.

Ralph McNutt, MESSENGER project scientist, said he finds the theory interesting.

"I think these guys may be on to something," McNutt told Discovery News. "There is certainly something going on that is very different than what is going on at Earth."

Sulfur was fingered long ago as an element that could be keeping Mercury's iron core partly molten, much like salt on a snowy driveway lowers the melting point of ice, turning it liquid even in temperatures below 32 degrees Fahrenheit.

MESSENGER is due back at Mercury in October. After a third flyby in 2009, the probe is scheduled to settle into orbit in March 2011 for a year-long, detailed study.

With regard to whether Mercury's core is snowing iron, McNutt said the probe should be able to provide detailed maps of Mercury's magnetic field, as well as chemical studies to identify sulfur and sulfur-rich deposits on the planet's surface.

"Trying to understand globally how much sulfur we're seeing might be important," McNutt said.

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Irene Klotz's blog: Free Space

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