Chie is a Japanese astronaut who has been living in orbital space for six months. Reserved and deeply thoughtful, she manages the profound isolation of space by making meticulous lists of things that irritate and surprise her. On the station, she is tasked with studying the effects of microgravity on brain activity and observing muscle growth in test mice.

Pietro is an Italian astronaut widely considered the "mind" of the station. Level-headed and highly experienced with thousands of space experiments, he views his work through a critical, humanistic lens rather than a purely mechanical one. He maintains a healthy cynicism regarding the billionaires funding space exploration, fully aware of the stark inequalities down on Earth.

Anton is one of two Russian cosmonauts aboard the space station. He is a thoughtful and ambitious man who has dreamed of lunar travel since his childhood. He currently wrestles with feelings of irrelevance as a new moon mission launches, while quietly worrying about a physical lump on his neck that threatens his career.

Shaun is an American astronaut considered the "soul" of the station's crew. Characterized by his quiet faith, he continually searches for meaning in the universe's design and humanity's place within it. He studies plant root growth aboard the station while privately agonizing over how to write a profound response to a news editorial about the new lunar mission.

Nell is a British astronaut with a background in research meteorology. Her lifelong drive to reach space stems from witnessing the Challenger disaster as a child, an event that instilled in her a profound reverence for astronauts. She combats the terrifying vastness of open space by likening her spacewalks to her earthly hobby of freediving.

Roman is a Russian cosmonaut and the current mission commander of the station. Known as the "hands" of the crew due to his precise dexterity with the station's machinery, he struggles intensely with feelings of confinement. To combat this isolation, he spends his free time operating a packet radio to connect with random strangers back on Earth.

A fisherman living on the island of Samar in the Philippines. He befriended Pietro years ago during the astronaut's honeymoon. He and his family live in the direct path of a devastating, rapidly approaching weather system.

A Canadian woman on Earth who connects with Roman via packet radio. Using her recently deceased husband's radio equipment, she engages the cosmonaut in a conversation about feelings of aimlessness and the mundane realities of daily life.

Chie's recently deceased mother and a survivor of the 1945 atomic bombing of Nagasaki. Her stoic toughness and defiant observation of the Apollo 11 moon landing profoundly shaped Chie's life path.

Shaun's childhood sweetheart and current wife on Earth. She intimately understands his intellectual struggles and sends him a postcard replicating an old school lecture to help him find meaning while drifting in orbit.

Nell's husband, who lives in Ireland and requires stability to avoid feeling overwhelmed by life. He struggles to fully comprehend Nell's drive for space exploration but stays connected through ongoing photo exchanges.

Anton's wife on Earth. Their marriage has been strained for an extended period, prompting Anton to heavily evaluate their future together as he contemplates his changing health and career prospects.