Movement of iron snow helps to maintain Mercurys magnetic field

May 8th, 2008 - 11:49 am ICT by admin  

Washington, May 8 (ANI): New scientific evidence has suggested that the movement of iron snow helps to maintain Mercurys magnetic field.

According to researchers from the University of Illinois (U of I) and Case Western Reserve University in the US, iron snow forms and falls toward the center of the planet, much like snowflakes form in Earths atmosphere and fall to the ground.

Mercurys snowing core opens up new scenarios where convection may originate and generate global magnetic fields, said U of I Geology professor Jie Li. Our findings have direct implications for understanding the nature and evolution of Mercurys core, and those of other planets and moons, he added.

Mercury is the innermost planet in our solar system and, other than Earth, the only terrestrial planet that possesses a global magnetic field.

Discovered in the 1970s by NASAs Mariner 10 spacecraft, Mercurys magnetic field is about 100 times weaker than Earths. Most models cannot account for such a weak magnetic field.

Made mostly of iron, Mercurys core is also thought to contain sulfur, which lowers the melting point of iron and plays an important role in producing the planets magnetic field.

Recent Earth-based radar measurements of Mercurys rotation revealed a slight rocking motion that implied the planets core is at least partially molten, said Illinois graduate student Bin Chen, the papers lead author.

But, in the absence of seismological data from the planet, we know very little about its core, he added.

To better understand the physical state of Mercurys core, the researchers used a multi-anvil apparatus to study the melting behavior of an iron-sulfur mixture at high pressures and high temperatures.

In each experiment, an iron-sulfur sample was compressed to a specific pressure and heated to a specific temperature. The sample was then quenched, cut in two, and analyzed with a scanning electron microscope and an electron probe microanalyzer.

Rapid quenching preserves the samples texture, which reveals the separation of the solid and liquid phases, and the sulfur content in each phase, said Chen. Based on our experimental results, we can infer what is going on in Mercurys core, he added.

As the molten, iron-sulfur mixture in the outer core slowly cools, iron atoms condense into cubic flakes that fall toward the planets center.

As the iron snow sinks and the lighter, sulfur- rich liquid rises, convection currents are created that power the dynamo and produce the planet’s weak magnetic field.

According to the researchers, Mercurys core is most likely precipitating iron snow in two distinct zones. This double-snow state may be unique among the terrestrial planets and terrestrial-like moons in our solar system. (ANI)

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