My bet is on human spacescrap. I did a thesis on the Mars rover once. It's a bit vague now (been more than 10 years ago), but in order to land safely, there was a whole dismantling of junk before parachutes could be deployed. And without an atmosphere to burn up falling debris, all that stuff is probably still on the surface somewhere.Human spacescrap or Alien spacescrap?
Cybermen. Can't be Daleks.
I've been waiting for someone to make DW references.Maybe it's a Cyberman. Someone got the Doctor on speeddial?