Bobbie is a protagonist and one of the four point-of-view characters. She is in her twenties and is a gunnery sergeant in the Martian Marine Corps—a highly skilled soldier. Her training has made her proficient at handling all manner of weapons. Bobbie grew up on Mars with several brothers and a father who was a Marine; she followed in his footsteps. In boot camp, when Bobbie learned about Force Recon, which accepts only the most elite Marines, she decided to become one. She was first in her class by a landslide.

Bobbie is a tall, well-built woman, partly due to growing up in Martian gravity and partly due to her Polynesian ancestry. She is in excellent physical shape and has great endurance. Bobbie is attached to her Goliath III powered armor, which was custom-built to fit her, even though the model is considered outdated now. When she is in her armor, Bobbie feels like a superhero, since it gives her incredible strength. But Bobbie’s skill as a soldier also lies in strategic thinking. She reviews video of the hybrid creatures’ attacks to understand how they move and fight, so she can figure out how to respond. Bobbie prefers decisive action to Avasarala’s political gamesmanship, but also feels admiration and even affection for the older woman.

Bobbie is honest, forthright, and not manipulative. Impatient with the indirectness of diplomacy, she demands, in the middle of Mars-Earth negotiations, to talk about the creatures that attacked Ganymede. Bobbie’s reliance on her strength can also be detrimental: She is so afraid to show weakness that she refuses, at first, to deal with the grief she feels at losing her squad mates, instead taking refuge in a quest of vengeance. However, she eventually comes to terms with her trauma. At the end of the novel, with her mission complete, Bobbie wonders what comes next for her. She decides to reconnect with her family and think about her future.

Avasarala is a protagonist and one of the four point-of-view characters. When the novel opens, she is an undersecretary of executive administration in the UN. Despite this nominal low position, Avasarala is effectively the third most powerful person in Earth’s government in terms of influence, after the secretary-general and Secretary of Executive Administration Errinwright. She has risen through the ranks through intelligence, sheer tenacity, and a hard-shelled persona that her husband, Arjun, calls “the mask” (54): She has an unexpectedly abrupt, abrasive manner and swears frequently to project strength. Avasarala was born and raised on Earth and is of South Asian descent. She typically wears a sari and her favorite snack is pistachios, which she munches on even in the most stressful situations.

Avasarala feels that “[h]er life had been about control, talking and bullying and teasing whoever needed it until the world turned the direction she wanted it to” (253). It is ironic that she calls Holden self-righteous when she is similarly single-minded in the pursuit of her moral north: protecting young people and children from war. She respects talent, integrity, and basic decency, and she deeply loves her husband and grandchildren, who bring out her softer side. Avasarala is haunted by the loss of her son, who was killed in a skiing accident when he was 15.

Avasarala uses whatever influence and resources she can muster to oppose the novel’s antagonists. When she realizes Errinwright has been cultivating the protomolecule, suborning Nguyen and Soren to his ends, Avasarala allies with Holden’s crew, Bobbie, and the still loyal Admiral Souther to take Errinwright and Nguyen down. These allegiances not only demonstrate her extreme canny and ability to think several steps ahead, but also demonstrate her willingness to work with anyone whose motivations she respects. After using her diplomatic skills to peel off Nguyen’s fleet until he is left alone and defenseless in the climactic battle, Avasarala parlays the victory into a promotion: She gets Errinwright’s job, which will mean more power and influence, as well as more bureaucratic headaches.

Prax is a protagonist and one of the four point-of-view characters. Prax, the mild-mannered son of a scholar, grew up on the outer planets. He is of East Asian descent. Prax has a PhD in botany; he conducts research on Ganymede to genetically engineer soybeans to be a nutritious food source for those living far from Earth. He is an excellent scientist, pursuing his experiments with determination and undaunted by failure. Prax is proud of the work he has done, which he sees as crucial to sustaining human life on the colonies. Holden notes, “he had probably been a very good scientist. Thrilled by small victories, undeterred by setbacks. Plodding along until he got to where he needed to be” (482).

Prax’s ex-wife Nicola left when she became unhappy with their life on Ganymede. This left him to be a single father to four-year-old Mei, whose immune system deficiency disease means she needs daily medicine and professional care. Mei is the center of Prax’s life, and when she goes missing, he does everything he can to save her.

Prax is named for Praxidike, an ancient Greek goddess of justice and vengeance. This suits Prax’s mission in the novel, which is to find and reclaim Mei, stop the protomolecule experiments, and secure peace in the solar system, however short-lived. Prax’s ambition is to help make the world a better place, which is why Avasarala appoints him to lead the rebuilding efforts on Ganymede so it can again become a source of food production and a child-bearing refuge.

Naomi is a supporting character, part of the crew of the Rocinante, and the voice of calm and reason in the novel. She is a Belter, meaning she grew up on the outer planets, where the gravity difference leads people to develop tall, thin body frames. She has long, dark, curly hair that she usually wears pulled back. She is described as “a striking mix of Asian, South American, and African that was unusual even in the melting pot of the Belt” (21).

Naomi is fiercely intelligent. She has two master’s degrees and was offered a scholarship for a PhD on Ceres Station, but turned it down. She likes the freedom of working aboard the Rocinante, as long as she can support their mission. Naomi is the executive officer (XO) of the Rocinante, in charge of operations and second in command. Naomi loves Holden but isn’t sentimental enough to say it out loud; instead, she pushes him to reflect on his hero fantasies and to reimagine himself as a team leader instead. She provides a balanced, thoughtful restraint to Holden’s tendency to be brash. She also doesn’t agree with his wish to have a baby, but doesn’t say why.

Amos is a supporting character and a crew member of the Rocinante. He describes himself as a mechanic, and there is little that Amos cannot fix, given the right tools. He is a stoic and capable man who is not sentimental but is uncompromising about his moral compass. He’s described as a large man, mostly bald, who grew up on Earth. Avasarala, in researching him, learns that he was implicated, but not charged, in several murders on Earth and had an elective vasectomy as soon as he was of legal age.

Amos at all times projects a physically intimidating lethality. As Holden describes it, “Amos had mastered a sort of constant glower that made people automatically put him onto their ‘not to be fucked with’ list” (135). When Avasarala shows the crew footage of the monstrous hybrid attacking Marines on Ganymede, she notes that Amos “watched with the calm reserve of a professional killer” (452). He is aware of and confident about his strengths: “Anything that kills me has already killed everyone else. I was born to be the last man standing” (286).

At the same time, Amos is kind, as shown in his tendency to look after Prax and his strong aversion to seeing children in danger—a personality trait that foreshadows revelations about his backstory later in the series. Amos enjoys playing with Mei once she is rescued and reunited with her father.