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also somewhat related:

Molten core may explain Mercury’s magnetic field

Mercury likely has a partly molten core, a new study indicates. This molten material may be generating the planet’s weak magnetic field, whose existence has been a puzzle since its discovery more than 30 years ago.
Earth’s magnetic field is generated by molten material in its core, but Mercury is so small that it was expected to have cooled and solidified long ago. But when NASA’s Mariner 10 spacecraft flew by the Sun-scorched planet in 1974 and 1975, it detected a magnetic field.

Big Snip

That would be possible if its core, thought to be mostly iron, contains some sulphur as well. “If you mix in a small amount of sulphur with iron, you can lower the melting temperature by several hundred kelvin,” Margot told New Scientist.

But if Mercury does contain some sulphur, its presence presents a puzzle of its own, since sulphur could not have condensed out of the early solar nebula so close to the Sun. This suggests that some of the building blocks, or planetesimals, that coalesced to form Mercury came from farther out, where sulphur could have condensed along with iron and other elements.

http://space.newscientist.com/article/dn11782-molten-core-may-explain-mercurys-magnetic-field.html