Julie is a pretty girl with a thin, lunar citizen's frame and long black hair.
She is a talented pinnace pilot; she won the first place in the Parrish/Dorn 500K race with her ship the Razorback, and beat the previous record, holding it for two years.
Some time during her twenties, while attending college, she joined the student activist group Far Horizons Foundation. Not long after, she eloped from her family on Luna and joined the associated organization Outer Planets Alliance (OPA), living in apartment 5151-I on Ceres Station, where she trained in low gravity jiu jitsu for five years gaining a purple belt, and being employed on Tycho Station.
Her parents were the owners of Mao-Kwikowski Mercantile, which supplied equipment to Protogen in preparation for the Eros incident, which made them privy to both the incident and the coming war in the Belt. Because of this, her mother Ariadne Mao tried to persuade her to return home to safety. When that proved unsuccessful, she hired Star Helix Security to locate her, a case that fell on Detective Miller.
However, it was too late: Julie was on an OPA mission aboard the Scopuli, which was boarded and infected with the protomolecule by the Protogen vessel the Anubis. Crews of both ships succumbed to the infection, but the infected Julie managed to tether the Anubis to the asteroid BA834024112 and escape to Eros, where she rented a hotel room and entered a three week long hibernation while the protomolecule altered her body. She managed to send a distress signal to the OPA's headquarters at Tycho Station and leave a message about the location of the Anubis, but died shortly after, and was discovered by Miller and Holden who also found her message and subsequently the Anubis and its protomolecule sample. Miller vowed to find out who and what killed Julie, and in his loneliness he constructed an imaginary apparition of Julie that accompanied him during his search.
Protogen got ahold of her body and the protomolecule sample, which they thought was lost after the Anubis disappeared. They brought her to the hospital on Eros and used her to initiate the Eros incident by infecting the entire Eros population of 1.5 million with the sample.
As Julie's infection was far more advanced, she became the "seed crystal" in the life-form that grew aboard the station, and her mind became the seat of its sentience. After the protomolecule managed to gain control over the station's spin reactors and utilize them, Julie directed the station towards Earth. Although this was first suspected to be a malicious act to infect Earth's population, Miller realized that Julie was just trying to return home when she talked about the Razorback through the station's PA system, and he managed to reach Julie's body and convince her to crash-land Eros on Venus instead.
A year later, when the protomolecule construct on Venus had formed the Ring outside Uranus's orbit and a flotilla including Jim Holden, Julie's sister Clarissa Melpomene Mao set out there to avenge their father Jules-Pierre Mao, who had been imprisoned after working with a branch of the United Nations to create human-protomolecule hybrid soldiers. When her mole Elio Casti, who was blind, was caught after installing a backdoor in the Rocinante, he created a digital render of Clarissa's face to show who had given him the contract. Holden, who was being haunted by Miller's protomolecule apparition, assumed it was Julie.