Like a Mere Orange Peel on a Giant Orange of Metal

Mercury is a giant ball of iron...

The Messenger robot explorer has been orbiting the planet Mercury for a year now.  The innermost planet in our solar system looks a little like our moon on the outside, but looks are deceiving.  Under its thin crust Mercury is mostly iron.  Like most of my interest in astronomy, this doesn't affect day to day life here on planet Earth very much I suppose, but understanding the cosmos and our place in it is always a good thing.  That, and having a reserve of nerdy cocktail party trivia worthy of Cliff Claven can come in handy from time to time (or so I'm told).   

Image credit: Case Western University by way of Discover Magazine