"New scientific evidence suggests that deep inside the planet Mercury, iron “snow” forms and falls toward the centre of the planet, much like snowflakes form in Earth’s atmosphere and fall to the ground.
The movement of this iron snow could be responsible for Mercury’s mysterious magnetic field..."

Read more (http://www.news.uiuc.edu/news/08/0507ironsnow.html)

How in the world would iron form snow? ...in a core...