In the near future, Earth is slowly being destroyed by overpopulation and pollution.
In search of a new place to live, scientists put their eyes on Mars and send unmanned probes with
algae that were bio-engineered to grow there. For twenty years this algae builds an atmosphere for
humans to breathe in, but one day all of the sudden, oxygen levels start to drop. Desperate
to find out why, all countries put their resources together to send the first manned mission to Mars.
The ship is called Mars-1 and it's too massive to launch from the surface of the planet, so the
crew shuttles to the high-orbit space station for a low-gravity launch to begin a six-month trip.
This crew is formed by the best scientific minds: pilot and commander Bowman, chief science officer
Chantilas, copilot Santen, mechanical systems engineer Gallagher, bio-engineer Burchenal,
and terraforming expert Pettengil. Coming with them is also AMEE, a multi-task robot that will
work as their Mars surface navigator. AMEE is powered by a helium nuclear power cell that will
keep it going for a while. For the following six months, the crew finds different ways to
keep themselves busy when they aren't working. Chantilas likes to talk a lot about philosophy and
religion, explaining he needs some big questions to be answered because science has failed him.
Gallagher likes to flirt with Bowman a lot and doesn't hesitate to walk on her in the shower,
pretending it was an accident. He is also the one in charge of the prelaunch diagnostics
checks on AMEE. Pettengill wants to see the robot in action and asks Gallagher for a demonstration,
so Gallagher decides to prank Pettengill. He changes AMEE from navigation mode to military
mode before giving it a marker and asking it to attack his friend, then AMEE proceeds to very
quickly stab Pettengill to show off how deadly it is. Eventually they get so bored of being up there
that Gallagher and Burchenal begin using the lab to make alcohol. At first, Bowman scolds them when
she finds out, but then she joins them and the whole crew ends up drinking together. On day 182,
the ship finally approaches Mars' orbit. The crew beings looking for HAB1, the automated habitat
where the probes were supposed to be growing the algae, when they suddenly get hit by a gamma
burst. Commander Bowman sends the rest of the crew to the safe area while she keeps an eye on
the system, and they wait for the burst to pass. Moments later, they discover the main power unit
is offline, so they'll have to leave for Mars now and look for HAB1 on foot. Once the crew is ready,
Bowman tries to activate the Extension Vehicle's auto-launch system but it doesn't work because of
the lack of power, so she has to stay behind and do it manually. The vehicle has a clumsy
lunch and Santen has trouble landing, meaning he has to get rid of their landing gear and AMEE. He
does manage to release the airbags, but when they finally land on Mars, the vehicle stills rolls
down a hill and takes serious damage. Meanwhile Bowman discovers that there are electrical fires
in several sections of the ship but the burst destroyed the automated fire extinguishers.
She rushes to grab the manual extinguisher to take care of the smallest fire, then she straps herself
to the emergency evacuation unit before opening a hatch. This way the vacuum sucks the fire out
of the ship. Then she works on getting the main power unit restored. On Mars, the crew has to
help Chantilas leave the vehicle because he was injured when he landed. Without AMEE they have no
way to navigate the planet and find HAB1 without getting lost, not to mention the radio and the
science package are broken. Gallagher remembers he has some panoramic photos the probes used to
send and compares them with the terrain, this will allow them to find the right way. Chantilas thinks
about all his philosophical questions and accepts his fate, so he asks the crew to leave him there.
His spleen's ruptured and there's serious internal bleeding, even if HAB1 has a medical unit he won't
make it in time. The crew says their goodbyes and Chantilas admits he's happy he at least got to see
Mars. Nearby, AMEE comes out from the landing gear and sends a drone to find the crew. On the ship,
Bowman manages to make communications work again, but since the guys' radio isn't working,
she can't get in contact with them. Then she uses the scanners to find HAB1, only to find
some bad news. She has no choice but to call Houston and inform them the crew won't survive.
The crew begins walking under the hot sun, and Burchenal is surprised to see there are no signs
of the algae - even if it all died, there should be some traces. When they finally make it to HAB1,
they discover it's absolutely destroyed. This couldn't have been done by the weather because
the structures had been designed to withstand even tornadoes, meaning something happened here.
There's food, no air, and no water, so the guys have no choice but to accept their fate. There
are only sixteen minutes of oxygen left and the crew chats about the people they left at home.
Santen decides to reminiscence near a cliff edge and points out that at least his piloting skills
can't be blamed for this, but Pettengill wants him to take some responsibility anyway. This triggers
a fight that ends with Pettengill hitting Santen, making him fall off the cliff. When Pettengill
goes back to the others, he tells them Santen ended things for himself. Minutes afterward,
their oxygen tanks run out, and Gallagher decides to open his helmet to take his last
breath. However to his shock, Gallagher discovers he can breathe just fine. Pettengill and Burchenal
follow his example and confirm they can breathe as well, although they can't explain why. Meanwhile
Bowman receives a message from Houston telling her the ship's orbit will fail in thirty-one hours but
they'll help her take off before then. Bowman is skeptical because ignition systems won't work. The
guys search HAB1 for anything useful again and find a radio, but it's broken too. This makes
Burchenal realize that the little rover Earth sent in '97 should have a radio as well, so they should
look for it. It's four kilometers from there and night is about to fall, thus they decide to leave
in the morning to avoid freezing. They use the remaining rocket fuel from HB1 to start a fire,
and its light allows AMEE to finally find them. Gallagher checks on the robot and notices it's
pretty damaged but the navigational device still works, which means he should shut AMEE down and
take the device out before it breaks too. AMEE hears this and reacts violently, pushing all
the men away when they try to deactivate it. Burchenal tries to hit it with a pipe,
but AMEE cuts it into little pieces before hitting the man, breaking one of his ribs. Then AMEE runs
away, reuniting with its drone on the way. Gallagher explains to the others that AMEE is
using guerrilla tactics and will come back later to kill them one by one, he also discovers the
robot jammed the transmitters to stop them from knowing where it is. In the morning,
Bowman manages to fix the ignition systems with the guidance of Houston, but she tells them she'll
try to save the crew before going back. The guys wake up and relieve themselves as a joke
to claim the territory in the name of humanity, then they go looking for the old rover. As soon
as they find it, Gallagher takes its radio and fixes the frequency to match the new one, but
no matter how hard they try, they can't contact Bowman. After two hours of failed tries, Bowman is
ready to leave for Earth and Gallagher's about to throw the radio away, but at that moment Houston
detects the rover's frequency and connects it to the ship. The guys finally get to talk to Bowman,
who hears the whole story and promises she'll find a way to rescue them. A few moments later,
Bowman contacts the guys again to inform them of a thirty-year-old Russian rock probe called Cosmos
that failed to launch many years ago. They'll have to fix it, but it's the only chance they got,
and they only have nineteen hours to do it before Bowman has to go back to Earth. Bowman also has
to keep working on some repairs, meaning she'll be in blackout on the dark side and she won't
talk to them again until later. Before hanging up, Gallagher tells Bowman he's glad to hear her voice
again, which makes her remember the time they almost kissed a few weeks ago. The guys begin
making their way to the probe, unaware that AMEE is following them. Suddenly Pettengill notices
something moving in the distance, but the others can't see it and ask him to keep moving. Nearby,
a bunch of alien insects begins moving in the same direction. Sometime later, Bowman checks on the
crew and asks Gallagher to take his comm off to talk in private. She informs him that the probe
only has room for two people and apologizes before going back to her work. Gallagher doesn't tell the
others about this issue yet and concentrates on helping Burchenal walk when his body begins
feeling weak because of the broken rib. When night falls, a big ice storm comes their way,
so the trio has to hide inside an opening on a hill. Thanks to the storm, AMEE has trouble coming
closer. The guys discuss the fact they don't have many hours left to find the probe, and Gallagher
finally confesses only two of them can make it back. He volunteers to stay behind, but Pettengill
doesn't believe him because he thinks Gallagher suspects him of killing Santen. Burchenal cuts in
and says he doesn't trust him either and confirms he indeed wants to leave Pettengill behind. A
few hours pass and Bowman receives a message from Houston telling her she needs to come back because
there's no way the crew survived that storm. She tries to contact the crew to no avail. It
turns out that after Gallagher and Burchenal fell asleep, Pettengill took the radio and ran away in
order to get to the probe first. Now that he is outside and exposed, AMEE sneak attacks him and
kills him in seconds. Burchenal and Gallagher see this on the suit comms and come out of the cave to
retrieve the radio. On their way to Pettengill's body, Burchenal is shocked to see algae,
and he can't understand why it only grows here. Gallagher retrieves the radio and tries to contact
Bowman while Burchenal looks more closely at the body, unaware that the bugs are running inside
the suit. Using a torch lighter, Burchenal tries to cut the suit open, but this ignites the little
aliens. Burchenal finally notices them and as he captures two of them, he deduces they're nematodes
who have been eating the algae. This explains why the plant suddenly started disappearing,
the nematodes eat it and produce oxygen in return as if they were trees. The more the guys walk, the
more algae they find. Burchenal begins dripping blood from his mouth because of his broken rib and
gets the attention of the bugs, which attack him by eating through his suit. Accepting his fate,
Burchenal throws his suit to Gallagher so he can have extra air for the trip, he also gives him
the tube with the bugs so Earth can study them and produce cleaner air. Then Burchenal waits for the
insects to cover his body and lights the torch to bring all the little aliens down with him. Bowman
sees all this from the ship and calls Gallagher to check on him. After explaining what happened,
Gallagher admits he's ready to give up, but Bowman changes his mind by pointing out he can't let the
crew's sacrifices be in vain. Gallagher puts himself together and runs until he finds the
probe, which he immediately begins working on with Bowman's guidance. The system works
but unfortunately the probe's battery is dead, so Gallagher's stuck here after all. Thinking this is
the end, Gallagher tells Bowman that he misses her and that he should've kissed her. Bowman agrees
and with tears in her eyes, she begins getting ready to return. At that moment, AMEE's drone
finds Gallagher, and he realizes it has batteries he could steal. He immediately begins preparing
a trap using the probe itself, letting AMEE come as close as it wants. When the robot is about to
go for his heart, Gallagher dodges the attack and releases an airbag soaked in fuel that traps AMEE,
allowing Gallagher to set it on fire. At that moment, AMEE activates its self-destruct system,
so Gallagher rushes to take out the battery and jumps out of the way right before the
drone crashes against AMEE to make it explode. Afterward, Gallagher finishes fixing the probe
and launches it with him inside to go after Bowman, who is about to leave for Earth.
Unfortunately the probe loses power in the middle of the way, but Bowman sees it and uses the space
walk rope to jump off the ship and retrieve the probe. Because of the lack of power, the
probe doesn't have oxygen either, so by the time Bowman opens it Gallagher is unconscious. Bowman
takes Gallagher's suit off and begins applying CPR until Gallagher wakes up, happily asking her
to take them home. Sometime later, Bowman gets a message from Houston after they took a look
at the information about the insects; apparently everyone on Earth thinks of Gallagher as a hero
now. Gallagher reveals he's also brought a rock from Mars to give to Chantilas' granddaughter as
a memento. Bowman can see Gallagher has grown a lot and finally kisses him, thinking about
how they have six months to get to know each other better before they make it to Earth.