Definitely the exclusion zone on Mars with heroic modifier active. If you have team mates to help it goes much faster - all you need to do is stand together and you will all get glimmer for every kill. My method: pop resupply code, kill all enemies that drop from the first ship, then run out to the right hand side and stand on top of the dome building. Kill all the enemies from the second ship except the two phanlax's with shields, then let them two enemies kill you. If you accidentally kill all the enemies go to orbit. When you go to select the mission press square for a restart, but then press square again to start the mission. EDIT - if you keep the network keys that drop in your vault then you can essentially store a shit tonne more glimmer. Don't cash them in! (Well that's what I do anyways)