The Waters of Mars sees the return of the Sanctuary Base 6 space suit borrowed by The Doctor some three years earlier in the 2006 two part story; The Impossible Planet and The Satan Pit.
It’s probably a budgeting issue that made them reuse the suit from a previous story but it does add a nice touch of continuity as we never actually see the Doctor give it back at the end of The Satan Pit.
This casual thieving of costumes might also explain why the TARDIS has need for such a capacious wardrobe. So raise your hand if you've ever borrowed something that didn't belong to you and sort of forgot to give it back.
Guilty it seems but then that's how he acquired the TARDIS so he's been at it from the start.