Our Dawn mission to the asteroid belt is no ordinary deep space expedition and ion propulsion is no longer the stuff of sci-fi. Instead of traditional chemical rockets, the spacecraft uses sophisticated ion engines for propulsion. This enabled Dawn to become the first mission to orbit not one, but two different worlds — first the giant asteroid Vesta and now the dwarf planet Ceres. Here are 10 things to know about this trailblazing mission: https://nasa.tumblr.com/post/165761482994/solar-system-things-to-know-this-week
