Iris Sullivan, called “Sully” by all of the characters, is the protagonist of the Aether’s narrative arc. Sully’s primary workstation on board the Aether is the communication pod, where she gathers data received from the Jovian probes and eventually scans radio frequencies from Earth in an attempt to find evidence of remaining life.

Sully’s primary arc is emotional, involving both her struggles with Human and Environmental Connection and her guilt over having pursued her passion rather than being a traditional mother. Trapped in memory like the rest of the crew, Sully recalls her early childhood as the only daughter of a highly intelligent single mother and scientist, Jean, whom Sully remembers idolizing. However, Sully’s memories of her mother are tinged with grief due to the loss she felt when Jean married Sully’s stepfather and devoted herself to the full-time parenting of Sully’s half siblings. Even before her mother’s passing, Sully felt alone in the world.

Sully’s memories also center on her own child, Lucy, and her ex-husband, Jack. Her ritual of touching Lucy’s photo every morning illustrates the depth of Sully’s love for her daughter, but self-recrimination plagues her. Sully always dreamed of being an astronaut, and landing a spot on the Jovian mission was the pinnacle of her career.