I think its earth too..... when he jumps to the stereo diagram, it shows earth would be to the right, then venus, then Mercury. When you see the diagram in motion, the camera and earth are almost in line with each other as they go around together, making it look in the camera view like it's focused on earth.... I bet after a few weeks from that shot that far right planet will start moving faster across the camera fov.... at least that's what the diagram shows..