Continuity mistake: In the earlier scenes on the planet's surface when the men still have their helmets on, it appears that the cameramen were also wearing space suits so that they would appear as crewmen on the visor reflections. Still too many people visible though.
Continuity mistake: In every view of the front of Mars 1, you can clearly see the landing pod still attached, even when it's on Mars' surface.
Continuity mistake: If you look at the back of Mars I, the "wings" that come out at the back change position. In one shot, they are in a typical five point star, then in another shot, they are in a six point star configuration with the one to the bottom missing.