Goofs

The talk used to distract the monster includes talk from dead characters.

Despite the vertical takeoffs and landings on Mars, nothing, including the grenades and gas bombs, is battened down or secured to the decks or bulkheads.

The doors open and close awkwardly. For example, when Carruthers ducks into the outer chamber after the effort to electrocute the monster fails, the door slides shut like it is spring-loaded. A moment later, the door opens but not all the way. Then, when the colonel jumps in again, the door closes in jerky motions.

The spaceship's different floors are never in order. For instance, Keinholz is on the top floor; he goes down one floor, looks around, then goes down another floor. This floor is the one with Carruthers and Eric playing chess. After Carruthers hears a scream he goes up the ladder to ask Keinholz if he had heard the noise; Carruthers peaks out of the hatch and is on the top floor, skipping the second floor Keinholz had to go through.

After "It" attacks Van Heusen and tears his left boot and foot to shreds, his boot is clearly unscathed when another crew member drags him away from the hatch.

Van Heusen opens the reactor shield to try to kill the monster, but it smashes through the door to escape. He doesn't reseal the shield, though. The adjoining space, the one with the man with the broken leg, should have been flooded with deadly radiation ("enough to kill a hundred men" as Van Heusen notes).

At around the ten-minute mark, as the ship is leaving Mars, in the control room we see a video screen showing the receding planet. But it's clearly Earth, not Mars.

On the way back from Mars we see a comet through the porthole. This comet should not have arched at all in relation to the spaceship. [Reference for changing this post: meteorites are meteors that make it through the Earth's atmosphere and hit the Earth. A rock in space with a tail is a comet. A rock in Earth's atmosphere is a meteor, if it makes it to the Earth, it's then called a meteorite.]

They use gas bombs on the monster yet are not affected by the gas when they take off their masks. The air in the space ship would be recirculated and would spread throughout the ship taking the gas with it.

The space helmets lack faceplates. When Carruthers and Calder exit the ship, Calder is seen to reach into his helmet and scratch his nose.

In the top level control room, the crew fires a bazooka at "It" twice. However, they don't reload after the first shot. Also, there is no back-blast from the weapon.

The monster bends a wooden stock rifle as if it were metal, or rubber.

The bazooka is not even loaded with a rocket. We can see control panel through the bazooka tube when Carruthers handles it few moments before he checks oxygen consumption.

When the crew uses gas grenades on the monster, the gas clouds drift up into the upper level, necessitating use of gas masks. However, the injured major and both female crew members are on the same level, at the back of the room, without gas masks.

One doesn't get an idea of the size of the rocket ship until the two astronauts "walk" on the outside. At that point one can see that, using the astronauts as comparisons, the the diameter of the rocket is not very large, perhaps barely wide enough for four or five people standing side-by-side. However, the inside scenes show the rocket to be quite roomy, large enough for smaller rooms around the perimeter of the interior space without crowding the astronauts too much in the center.

The ship is shown as going up with the stars going down, but in one scene not too long after they take off, a crew member looks through a porthole and the stars are going from right to left. A shooting star can be seen. The next shot is a long shot of the porthole and the stars are going from top to bottom on the screen, then suddenly they just stop.

Just before the crew goes down through the hatchway, about 3/4 of the way through the film, a hand appears on the far left, indicating that something should go down or sit down. Nothing is seen to go down (no doors or hatches or actors) but the hand is clearly seen to be going up and down.

When Lt. Calder says he left the ''C'' compartment door open, you can see the reflective mono filament pulling the door closed.

Bullets, grenades, gas bombs, electricity and even a healthy dose of atomic radiation seemingly fail to harm the creature. But when Lt. James Calder is pinned between the induction pumps because of an injured leg, he manages to hold the creature at bay with a portable blow torch.

The man who addresses the press states that the 2nd spaceship was sent 2 months ago, from that moment. He informs the press that the 2nd spaceship has sent a message that they're ready to return. Yet Carruthers says he will spend the next 4 months with the crew, in their return to earth. Why is that, if the 2nd spaceship was able to reach Mars and locate Carruthers in their 2 month time-line.

Why would Carruthers need to kill his shipmates, to hoard a ten-year supply of food rations, if, by 1973, American rocket science was supposed to be so advanced that one could be launched to Mars every four months? Van Heusen's accusation would have made more sense if the writers had included the real-world science fact that a launch window, between Earth and Mars, only opens roughly once every two years.

For a ship that's on an ostensibly peaceful rescue mission, there certainly are a lot of weapons on board (pistols, rifles, grenades, tear gas, even a bazooka).

Towards the end of the film, when the crew has to remain on the upper deck, when 2 crew members are aiming the bazooka towards the last remaining hatch, the shadow of the boom mic sweeps from the 2 men on the bazooka, to the rest of the cast discussing their next plans.