The Doctor was still exploring the station and becoming familiar with the setting, so much that he's forgone sleep and keeping up with everyone. He's moving down a corridor, actually munching on some crisps from a bag when he spots Martha. Quickly stuffing the remaining bag in a pocket, he's quick to swallow the food in his mouth before greeting her.
"Hey there!" Unfortunately he's a bit obvious to her change in wardrobe, not recognizing the rather tight nature of her clothes, though he did notice the scars missing.