A girl who writes letters throughout the story, sharing her thoughts and emotions about the rover and her family, providing insight into her character and growth over time.

A scientist working on Resilience, known for her precise and efficient coding, who maintains a professional relationship with the rover but gradually opens up emotionally.

Resilience's drone companion whose growing understanding of emotions strengthens his friendship with Resilience and plays a vital role in their mission on Mars.

A test rover that emphasizes logic over emotions and initially influences Resilience's thinking, yet eventually learns to appreciate a different perspective by the story's end.

A satellite observing events on Mars, dedicated to aiding rovers, who begins to acknowledge the value of friendship and emotional connections between Resilience and Fly.

A relaxed scientist involved with Resilience, who befriends the rover and is instrumental in motivating and encouraging him throughout his mission.