You know, i've been reading all this stuff of Destiny on this website. I honestly think that being a Vanguard is a Guardian that can travel to other planets. For the non-updated things in the story: i.e the Cabaul race, or more info on mars/venus, it says waiting report from the Vanguard. It makes sense, because being called a guardian sort of implies staying on earth to protect it. I know it doesnt sound as spectacular as some other speculations, but im calling this one out, and if i'm right, you all owe me a cookie.