The physical configuration of Mars-1 changes throughout the film. In some shots, the MEV lander is docked at the front of the spacecraft. In other shots, the MEV dock is empty before launch.
(around 19:37) When commander Bowman is trying to activate manual override on the launch system she can be seen taking a small metal hanging crucifix down from the overhead controls then in the next shot it is there again and she takes it down a second time.
The crew and even the ship's computer randomly switch back and forth between using the metric system and the English system of measurements. One example: Bowman directs ground crew to walk "100 kilometers" to the Russian rock sample vehicle, yet when the ice storm hits them, the ship's computer informs Bowman that the ice storm is producing maximum sustained winds of "111 miles per hour; temperature, negative 50 degrees Fahrenheit".
Gravity on Mars is much weaker than shown in the film.
When commander Bowman vented all the air from MARS-1, the pressure difference blew pieces of glass and debris into space and should have blown all free floating objects out into space as well. After bowman restores gravity, several objects fall to the floor and were not affected by the pressure difference at all. At 41 minutes, there is broken glass all over the table Bowman sits down at and all the chairs are exactly were the crew left them not being moved at all by the pressure difference.
(at around 1h 18 mins) The creatures on Mars are called nematodes, which are unsegmented worms. With jointed exoskeletons and paired legs and arms, the creatures resemble arthropods.
While orbiting Mars, the orbiter would be in darkness for a few hours, not the entire Martian night.
(at around 29 mins) After Bowman puts out the fire and restores power in the ship, the ship resumes spinning and the artificial gravity goes back into effect. When this happens Bowman and the various floating objects immediately fall "down" to the floor. In space there is no down, so objects could just as easily fall up or to the side. What's more, artificial gravity produced by centrifugal force does not attract objects. Object in free fall would continue to remain in free fall until they came to rest onto the rotating surface, at which point the effect of artificial gravity would then be felt.
Though the nematodes (falsely named anyway as they are a kind of arthropods) eat the algae that was sent from Earth, it's impossible that they are the only life on Mars and previously had nothing to eat. The nematodes' usual prey are likely to be found underground.
After the ground crew crashes on Mars, sunrise clearly shows the sun in a blue sky, despite the lack of water on Mars. The color of the sky is an atmospheric effect (blue light scatters more than red or green), and has nothing to do with nearby bodies of water.
(at around 12 mins) When Burchenal explains that humans have killed all frogs on Earth, he mentions that they have become extinct because they could not breathe through their skin anymore. Yet, the recent declines in frogs population are also likely to come from diseases, habitat destruction and climate change. The decreasing of the ozone layer is also supposed to play an important part in these declines.
The Russian text in KOSMOS launch ship computer menu is just a random set of symbols.
During the ice storm on Mars, no one's breath is visible on the ground, despite sub-freezing temperatures.
(at around 1 h 10 mins) In a shot of Mars from space, the sun is in the top-right corner of the frame, casting a row of lens flare spots slanting slightly down to the left. This is impossible, as a lens flare always passes from the light source through the absolute center of the lens. A correct CGI-made lens flare can be seen at 57 mins, complete with a blue streak as it would occur with some anamorphic lenses.
Bowman instructs Gallagher to launch Cosmos: "Okay, now, this thing has two settings: on and off." The probe has two buttons written in Russian: "annulirovat'" (cancel) and "proba" (trial), however, "proba" is upside-down.
(at around 43 mins) When Lt. Ted Santen and Chip Pettengill are arguing near the cliff, 3 holes are visible in the chin area of their 'air-tight' helmets.
(at around 35 mins) In the orbiter, as Bowman restores power/oxygen and tries to restore communications, she flips through a bunch of switches in rapid succession. One switch breaks off and falls.
The temperature on the surface of mars in -80º F yet the crew remove their snoopy hats and they keep their helmets stowed, sleeping bare-headed. Plus while there is heat reflective sheeting to be found, it is not used for conserving heat.
When radio communications are first established there is a closeup shot of Bowman against a dark background with a backlight. A great deal of dust can be seen moving in the air behind Bowman. In an enclosed space such as a space ship the dust would be constantly filtered out.
Although artistic license is clearly at play in this movie, one element that is particularly incredulous is that out of the entire population of the planet the six astronauts chosen for the mission includes a creep, a coward, an egotist, and a man in his early sixties, plus all but one of them are Americans.
The 1997 Pathfinder/Sojourner is labeled "UISA", like the crew's 2052 equipment. The Pathfinder/Sojourner was launched by NASA, and included the US flag and the Jet Propulsion Laboratory logos.
When the astronauts are standing on the Martian cliff the camera and crew are reflected in their face shields, hidden under a black tarp.
The two moons of Mars, Deimos and Phobos, are so small that they don't block enough light to cast shadows on the Martian surface.
FLIPPED SHOT: During the opening credits, as "Warner Bros. Pictures" is displayed on the screen, Earth is in the background, with the US east coast (including a reversed outline of Florida) on the left of the screen. As the camera pulls back, the US west coast is on the right side of the screen. In the following shot, when the international space station is shown with a shuttle approaching, the US coastline is correct.
(at 42:35) When Pettengill goes to talk to santen on the edge of the cliff the sun is on the left of both santen and pettengill however in the next frame it is now on the right of Pettengill and behind him when the camera switches to show their faces.
Mars lost its magnetosphere several billion years ago, allowing radiation to react more strongly with the Martian ionosphere and keeping the atmosphere too thin to support human life. This is due mainly to the cooling off of the Martian core, whose magnetic field supports atmospheric retention. Using algae to re-oxygenate the planet would be futile; the atmosphere is too thin to keep the oxygen from escaping into space.
(at around 1h 18 mins) After Gallagher retrieves the radio from Pettengill, he tries calling Bowman with no result. He says Mars 1 may still be on the night side of Mars. It is clearly night, so Mars 1 should be in range.
(at around 1h 3 mins) Burchenal says he is an expert in genetics, yet he refers to the 4 DNA nucleotides as A, G, T and P. They're actually A, C, G, and T. It's corrected in the German dubbed version.
(at around 50 mins) Bowman says it will take 40 minutes for Houston to reply. The signal travels at the speed of light, but the distance from Mars to Earth varies. On Feb. 5, 2057, it would take 5.7 minutes to reach Earth, which means an 11.4 minute response time (not including time for Houston to formulate a reply).
The geneticist says he writes code with "A, G, T, P". It should be "A, G, T, C".
As Bowman is preparing to rescue Gallagher, Lucille (the computer) tells her that Gallagher's craft is "point 3" kilometres away. 300 metres would've been a clearer way to phrase this.
When the characters are on Mars and realize they are able to breath Burchenal (Tom Sizemore) calls Pettengil (Simon Baker) by the wrong character name "Santen" (Benjamin Bratt) who was just knocked off the cliff.