Plot hole: Further to the comments about the Lunar Lander being useless as a Mars Lander - who is going to believe that three men spent eighteen months crammed into a tiny Lunar Command Module? Not only would they go out of their minds, where would they store the tonnes of water and food they would need in that tiny capsule? How could the Service Module carry enough oxygen or have enough battery power to make the trip?
Plot hole: The aliens provide coordinates for a place to make a rendezvous with humans but do not specify a time. It's possible they're monitoring and will arrive when they see enough humans gathering at Devil's Tower, but the humans seem to expect the aliens to come more or less exactly when they actually do, somehow.
Suggested correction: Scientists were prepared for the aliens and knew when and where they would arrive, as seen by the extensive complex built at Devil's Tower. However, as Claude Lacombe, the French scientist, speculates towards the end, hundreds of humans may have had the Devil's Tower image recently implanted in their minds, saying they were "invited" but never made the connection. Neery figured it out and was compelled to go there at that time. Neery was then allowed to join a group of trained volunteers that were already prepared to go on the ship, while the previous "abductees" were being returned to Earth.
The aliens had not given a time to meet. The scientists may be taking it on faith that the aliens will know that they've arrived at Devil's Tower and are ready, but the way the subject of timing is left unaddressed on screen feels like an oversight.
We don't know for certain if the scientists were given a specific time, but it appears they were, or at least a general window. The long-lost objects, like the ship and the military aircraft, suddenly showing up in the desert, is an indication the process has started. If humans were given the precise location where the alien ship would arrive (Devil's Tower), then, logically, the aliens would also communicate when. The scientists were communicating with the aliens using tonal sounds. Early on, the scientists received map coordinates through dish satellites as repeating pulses. They would likely receive time information the same way. As often happens in movies, this info may be something that got edited out of the film, causing an inconsistency.
This might be one of those edge cases. Under most circumstances I'd agree we could assume arrangements were made off-screen by virtue of the fact that the rendezvous occurs successfully in the first place; but in the context of this movie, in which any and all forms of contact with the aliens is treated as profound and significant, leaving it unaddressed (not even with a line of dialogue) comes off like a plot hole. I suppose we'll just have to let our fellow website readers decide.
Plot hole: Despite no one actually seeing the landing site of the meteorite, the sheriff takes his boat and the divers to the exact location of the rock. They go down and immediately find it.
Suggested correction: You're assuming they travelled from Earth to Mars in the lander alone. The astronauts didn't do this when they went to the moon. The Lunar Lander was attached to the command module during the 3-day journey. When the astronauts reached the moon, they detached the lander from the command module and landed on the surface. It is reasonable to believe the astronauts for Capricorn One did the same thing, except on a much bigger ship for a journey that lasted over a year. We just never saw it.
Mike Lynch
The posting did not refer to the Lunar Lander, it referred to the tiny Lunar Command Module, the only part of the Saturn V that returned to Earth. From 44:00 to 48:08 of the film we see a live broadcast, supposedly from Martian orbit, showing all three astronauts crammed into a Lunar Command Module. The posting is absolutely correct.
This is another Deus ex Machina explanation for a blatant film mistake. The astronauts launched into orbit in a standard Saturn V rocket which could not possibly carry anything like a spacecraft large enough to make the trip to Mars. There is nothing in the film to suggest that there was a "much bigger ship" involved.
They are also shown seated in the tiny Apollo command module, supposedly transmitting messages from orbit around Mars. The posting is absolutely correct.
You're assuming the astronauts were launched in a standard Saturn V rocket, but with all the resources needed for a journey to Mars that took 18 months round trip, NASA would have to send them on a larger rocket to accommodate the required oxygen, water, food, spare parts, supplies, etc. needed to bring them back safely.
Mike Lynch
Did you watch the film? From 1:54 to 2:25 we see an establishing shot of a perfectly ordinary Saturn V rocket on the launch pad. From 6:05 to 6:43 we see all three astronauts strapped into the tiny, Lunar Command Module. As has already been pointed out from 44:00 to 48:08 we see a live broadcast, supposedly from Martian orbit, showing all three astronauts crammed into a Lunar Command Module. There is absolutely no mention of a larger spacecraft and none is ever shown.