Mission to Mercury Is the Stuff of Mystery Posted: 8/2/2004 12:00:00 AM Reads: 151 Submitted By:clayroy Category: Space Source: www.washingtonpost.comWhy is Mercury basically a gigantic iron ball? Why does it have a magnetic field? Why does it have a cloud of sodium gas surrounding it? Is the shiny stuff that fills the polar craters ice, and if so, where did it come from? COMMENTS Please log in to comment.