Sarah [Eva Green] is a French woman who has spent her life dreaming and training to become an astronaut. She learns that she is a late addition to the Proxima crew, an International Space Station mission designed to be the final precursor before a voyage to Mars. The news fills her with a mix of excitement and anxiety, because the mission will pull her away from Stella, her daughter, whom she has been the primary caregiver for since separating from her spouse.
Despite the thrill of the opportunity, the emotional cost weighs heavily. Sarah decides to leave Stella with her ex-spouse, Thomas Akerman, trusting that he can provide stability while she trains for the mission. On the NASA-style training ground, Sarah quickly discovers she is the only woman on the Mars team, and she faces initial hostility from the American captain, Mike Shannon. He makes no secret of his skepticism about her place on the team, preferring the familiar dynamics of male substitutes. Yet, as the days of training unfold, Sarah’s determination begins to win him over, and he starts to recognize the strength of her resolve.
The crew’s dynamic grows more complex as the crew’s life in space becomes a test of endurance, skill, and emotional resilience. Stella is allowed a single visit during training, and Sarah fights to secure more time with her daughter. The visit goes awkwardly at first; Stella’s nerves and restlessness spark tension, and she eventually slips away, leaving both Sarah and Mike shaken. The strain deepens when Stella unexpectedly leaves again the next day, this time while Sarah is still asleep, a reminder of how hard it is to balance two demanding worlds.
The emotional toll of separation weighs heavily on Sarah, but Mike’s occasional assurances begin to cut through the tension. He tells her, in plain terms, that it’s impossible to be a perfect mother or a perfect astronaut and that they are, after all, only human. Those words, spoken in a moment of vulnerability, echo through Sarah as she grapples with the limits of what she can give and what the mission will demand.
As the final pre-launch meeting approaches, the strain of the situation comes to a head. Stella and Thomas miss their flight, robbing Sarah of one last chance to say goodbye in person before she leaves Earth behind for two weeks of quarantine and the journey into space. The separation hits hard, and the emotional distance between mother and daughter feels almost insurmountable.
A poignant moment unfolds when Sarah and Stella finally share a moment through a pane of glass during quarantine. Stella reminds her mother of a promise to see the rocket together, and the broken promise tears at Sarah. In a bold, quiet defiance, she slips out of quarantine and wakes Stella early, choosing to give her a final memory of the mission she is about to embark on.
The launch itself becomes a profound culmination of love, sacrifice, and ambition. That evening, the rocket lifts off with Sarah aboard and a photograph of Stella by her side—a powerful image of a mother chasing a dream while carrying the memory of her child. On Earth, Thomas [Lars Eidinger] and a tearful Stella watch the launch, their faces reflecting the mix of worry, pride, and hope that defines this extraordinary moment. The mission begins with a mix of courage and vulnerability, signaling the extraordinary balance between personal sacrifice and human aspiration that drives Sarah forward.
