Sarah [Eva Green] Loreau, a French woman who has spent years dreaming and training to become an astronaut, learns she is a late addition to the Proxima crew, an International Space Station mission that serves as the final precursor before a mission to Mars. While she is thrilled to be included, she also carries the heavy weight of leaving Stella [Zélie Boulant] Akerman Loreau, her daughter who has depended on her as the primary caregiver since separating from her spouse, [Lars Eidinger] Thomas Akerman. The emotional conflict threads through her excitement, grounding it in the reality that parenthood and space travel rarely align perfectly.
Onboard, Sarah becomes the sole woman on the Mars mission, and she meets open hostility from the American captain, [Matt Dillon] Mike Shannon, who makes it clear that he would have preferred a male substitute to take her place. Despite the rough start, Sarah’s perseverance begins to win him over as he watches her determination during training. The dynamic between them evolves from tension to a guarded respect, a slow recognition that competence and care can coexist under pressure.
Training routines are intense and tightly scheduled, but Sarah fights to balance duty with her responsibilities as a mother. She asks for special allowances to allow Stella more time with her mother, hoping for moments that sustain their bond despite the looming separation. The day comes when Stella is allowed to visit once. What starts as a hopeful reunion quickly turns problematic: Stella grows anxious and bored, slips away, and returns to a state of unease that reignites friction between Sarah and Mike. The emotional strain of juggling both roles becomes palpable, and Sarah feels the weight of every decision she makes about Stella’s presence near the mission.
The next day, Stella leaves while Sarah is still asleep, a jarring reminder of how fragile the balance between family life and a spacefaring career can be. In a moment of vulnerability, Mike tries to offer comfort, telling her that it is impossible to be a perfect mother or astronaut and that they are only human. The exchange gives Sarah a fragile spark of reassurance, a reminder that imperfection is part of being human—even when the stakes are cosmic.
As the two-week quarantine looms before departure, Sarah faces a heartbreaking development: Stella and Thomas miss their flight, robbing her of a final, in-person farewell before she heads into space. The emotional toll deepens as she confronts the last chance to connect with her daughter just before launch. They do manage one final moment: Stella and Sarah share a gaze through a pane of glass, a bittersweet goodbye, as Stella reminds her mother of a promise to witness the rocket take off together, a promise that remains unfulfilled in that moment.
Devastated, Sarah defies the strict isolation and wakes Stella, bringing her to the launch site at dawn so they can be near the rocket one final time. That evening, the mission proceeds: the rocket rises into the sky with Sarah aboard, a photograph of Stella kept close by her side. Back on Earth, Thomas and a tearful Stella watch the launch, sharing in the triumph and the ache of a mother who reaches for the stars even as she leaves a piece of her heart behind. This story threads through themes of sacrifice, resilience, and the enduring bond between parent and child, framed against the awe of space exploration and the cost of chasing a dream.
