The Expanse Wiki
The Expanse Wiki
This article is a stub. You can help The Expanse Wiki by expanding it.

The protomolecule is an infectious agent of extra-terrestrial origin first discovered on Phoebe by the Martian Congressional Republic in 0 XTE. It has the ability to radically alter infected life forms and utilize their biomass in various ways.

Not a life-form in itself, the protomolecule is described by Antony Dresden Books • TV as "a set of free-floating instructions designed to adapt to and guide other replicating systems".[1] It is able to maintain and adapt its primary structure in a wide variety of conditions, and it has an affinity for carbon and silicon structures, but is likely anaerobic and will not degrade upon exposure to oxygen.[2] Naomi Nagata identified the substance aboard the Anubis as a "nano-fluid", revealing that the protomolecule is some form of nanotechnology, essentially functioning as a pseudo-biological "computers". As molecular nanomachines, the protomolecule uses ionizing radiation as an energy source. Its growth significantly accelerates if it is exposed to high doses of ionizing radiation, and it depends only on the abundance of such energy.

Extrasolar origins

The Protomolecule was sent by an alien civilization inside an interstellar asteroïd 2 billion years ago. This asteroïd was captured by Saturn's gravity to become one of its many moons we called Phoebe. Yet its intended destination was Earth. It is initially seen as a weapon since infected humans die.

However, The Investigator Books • TV informed James Holden Books • TV that the Protomolecule is not a weapon but a tool. It functions as an advanced pre-programmed platform created by the Ring Builders. The programming appears to be using alien world's biomass (with a preference to reproductive systems, i.e life) to build things. Therefore life doesn't "die" but is rather transformed.

Not a weapon, the Protomolecule turns out to be an incredibly flexible tool, capable of creating and functioning in and as a variety of purposes and objects, as we learn new ones every step throughout the series. In rudimentary terms, the Protomolecule could be described as an all-purpose real life hacking code that rewrites whatever it touches to suit its own ends.

The Protomolecule samples sent to the stars 2 billion years ago were panspermia-like molecular phage, invented and developed for massive galaxy exploration. Like the phages we know, it could only become active when it came into contact with a replication mechanism. On Earth, then primitive life would have provide enough to feed its impressive transformation process, hijacking any life or inanimate to nurture a mysterious growth. Yet the Protomolecule was not programmed to develop life. Its first goal is to create the infrastructure needed for interstellar travel and communication. Once it grew with enough bio-mass it moves to the outer limits of the targeted stellar system and builds a gate. It leads to a wormhole establishing a connection to its creators' galactic-wide Ring Network, a network of more than a thousand of other gates, opened on as many stellar sytems. In our world for example, it was bound to create the Sol Ring, our gate to access the whole network.

Another important use to the ancient aliens who created it is to develop suitable facilities on planets (power plant, data storage, fixing shop etc). Even milleniums later it activates their technology, like a fuel, somehow magically awakening drones, ship-reparing platforms, transportation lines, access to virtual libraries and so on in the many worlds behind the Ring Network gates.

The Protomolecule has a complex relationship with human brains. At times after its release humans discover several ways it has to guide, impact or divert individual consciousness but when absorbing living matter, the protomolecule, however, is not conscious. That's why it is a tool and not a form of alien life.

Protomolecule clusters

Clusters of microscopic Protomolecule

At some point between the Bracewell probe swarm launch and the present day, the civilization that invented and then scattered the protomolecule was attacked and seemingly destroyed by an as yet unidentified aggressor.

Humanity discovers the Protomolecule

Protogen's Experiments

Main article: Discovery on Phoebe

In 0 XTE, the MCR landed on Saturn's ice moon Phoebe to survey it for ice mining. When core samples from the moon were investigated, however, silicate samples were found, and the Martian government approached Protogen corporation from Earth as a co-sponsor of a long-term research facility. Protogen discovered the alien agent, dubbed it "the protomolecule", and began experimenting with it. Later, Protogen killed all Martian scientists on the Phoebe station to hide their discovery, but the goal of this killing is unclear. There are suspicions that Phoebe was likely first limited to laboratory scale protomolecule experiment developed as an initial identification of protomolecule properties/capabilities in action. Testing on living entities is a strong evidence of MCRN long term supremacy strategy to develop a weaponry against Earth.[Citation needed]

Placeholder other This article or section includes speculations, observations, or opinions possibly supported by elements in the books or the TV show.*
S01E08-Anubis Infection Closeup

Protomolecule on the Anubis reactor.

The samples of the protomolecule were placed in a safe onboard the Anubis Books • TV to be taken to another location. On the way, the Anubis would board the Scopuli and take prisoners to infect.[Citation needed] This would get out of control however, when the entire crew and prisoners became infected by protomolecule. The second, maybe even more likely scenario is that Scopuli was a lifeboat for some Belters personnel inluding Julie Mao Books • TV, escaped from Phoebe Station when Protogen launched its first protomolecular experiment.[Citation needed] When it becomes clear that some eyewitnesses survived, Anubis, with a sample of the original protomolecule on board, was ordered to destroy all other evidence of the Phoebe incident. Intentional or accidental, protomolecule infection killed crew members on both Scopuli and Anubis, but not Julie who was imprisoned in an isolated quarters after boarding.

Julie Mao survives taking the shuttle Anubis 1A to Eros. However, Julie was infected and eventually died at a hotel on Eros, where her body was found by the crew of the Rocinante Books • TV and Detective Miller Books • TV and later by a team of Protogen scientists led by Anthony Dresden. All subsequent samples of the protomolecule in the Sol System are just from Julie - patient-zero.

On Eros

S01E10-Kenzo taken

The protomolecule takes Kenzo Gabriel.

Main article: Protogen experiment on Eros Books • TV

Having found the protomolecule sample extracted from the body of Julie Mao, Protogen was able to make second protomolecular larger scale test by using this sample to infect the population of Eros as a controlled experiment to study and observe how the protomolecule would behave when fed with 100,000 humans. Upon the infection beginning, signals were sent to Thoth Station where it was studied.

Osiris Station experiments

The Osiris Station was a sister facility along with Thoth, where smaller protomolecule research was done.[3]

Project Caliban on Ganymede and Io

Closeup of HPH in Roci cargo bay-enhanced


Main article: Project Caliban

Project Caliban was a Protogen experiment to use the Protomolecule to create human-protomolecule Hybrids for use as supersoldier weapons. The Ganymede incident Books • TV took place eighteen months after the Eros incident Books • TV in 11XTE[4]. This was the first weapons test of the Hybrids, and the program continued until the end of Io Campaign Books • TV when the project was ended and Protogen was seized and shut down.

Eros incident

Main article: Eros incident Books • TV

In 9 XTE, the first major outbreak of the protomolecule, known as the Eros incident, took place. It was a controlled infection of the entire population of Eros, numbering one and a half million humans. With this amount of biomass, it was revealed that the protomolecule had the ability to create a hive mind of sorts, which integrated itself with the computer systems of Eros station.

Activity on Venus

Following the descent of Eros Station to the surface of Venus in 9 XTE, the protomolecule began rapidly reshaping the planet. Observers throughout the Sol system observed these changes with great interest, but, despite the wealth of data, the objectives of the alien organism remained obscure.

Protomolecule scan (It reaches out)

Holden undergoing scan for Protomolecule infection

The military science vessel Arboghast was tasked with observing Venus from orbit and relaying instrumental data to the UN. Eight months into her mission, the Arboghast received or emitted a brief radiation pulse of unknown nature and origin that interfered with all observing telescopes in the non-visible spectrum. Immediately following this, the entire vessel was disassembled into its structural components, down to the level of screws and bolts, methodically and with no discernible mechanism of action. The crew of 572 personnel were lost to vacuum exposure.

On Venus and beyond, the protomolecule hive mind displayed an ability for instantaneous communication, with events involving the substance anywhere in the system (mainly the activation or destruction of human-protomolecule hybrids) triggering a response from Venus' surface.

Sol Ring


the Sol gate is complete

In 12 XTE, the protomolecule launched a massive complex of structures just outside the orbit of Uranus and built a thousand-kilometer-wide object known as the Ring. This is the final stage of the protomolecule life cycle: to convert itself into a wormhole leading to the slow zone Books • TV and Ring Station Books • TV.

Conflict on Ilus

The protomolecule on the Rocinante activates the Ring builder remnant technology, leading to ghost Miller activating everything on the planet and using the Void bullet to deactivate everything on the planet including the clumbs of protomolecule on the Roci.

The stolen sample

Following the attack by the Free Navy on Tycho Station, the last known sample of the protomolecule is believed to be in the hands of the Free Navy. However, after the Free Navy Conflict, the whereabouts of the sample are unknown. In actuality, the samples had been given to Winston Duarte's rogue Martian fleet and taken to Laconia.

The Laconian system was kept secluded from the rest of the Interstellar human community over the next thirty years and using these new Protomolecule samples along with the discovered Ring Builder Empire shipyard Laconia Station developed new technologies.

People who fall into bad favor with the Laconians are put into isolated rooms where they are exposed to protomolecule and are used to activate protomolcule technology or to be tested on.

The Protomolecule's life cycle


The protomolecule can infect other life forms on contact (it is anaerobic, and cannot be transmitted through the air).[citation needed] While supposedly designed for use on simple, single-celled organisms[5], it is effective on multi-cellular life as well. In humans, it spreads internally and starts altering its host through a process that may take several weeks, during which the host hibernates, but which can be significantly sped up via exposure to ionizing radiation.


After awakening from hibernation, the host becomes disoriented and feverish, with symptoms similar to a hemorrhagic fever. Shortly after, a brown fluid begins leaking out of its orifices. Human hosts at this stage are nicknamed "vomit zombies" because of their tendency to stagger around, spewing the brown fluid, which is highly infectious to other creatures.


The protomolecule will eventually begin to alter its host in a variety of ways, most frequently melding the biomass of multiple hosts and repurposing specific organs to carry out new functions.[6] Changes beyond this point seem to be highly variable and unpredictable, but recognizable features that might be incorporated in the resulting structures are black filaments, brown slime and blue luminescence.

Hive mind

The protomolecule's original construction appears tuned for simple unicellular life[7], though able to operate with a wide variety of hosts including advanced, intelligent multi-cellular organisms. Given enough biomass from several intelligent hosts, the protomolecule is able to create a hive mind. In the only known instance of this occurring, an initial victim (Julie Mao) was used as a "seed" or template for the nascent consciousness, which then guided the utilization of all subsequent biomass.

It is unclear whether normal functioning with an active connection to its creators would result in a host gaining some measure of control over the development and behavior of the resulting structures as Julie did.



  1. The Expanse Novel Leviathan Wakes - Chapter 34: Miller
  2. The Expanse Novel Leviathan Wakes - Chapter 32: Miller
  3. The Expanse Novella The Vital Abyss
  4. The Expanse Novel Caliban's War - Chapter 1: Bobbie
  5. The Expanse Novel Abaddon's Gate - Prologue: Manéo
  6. The Expanse Novel Leviathan Wakes - Chapter 33: Holden
  7. The Expanse Novel Abaddon's Gate - Prologue: Manéo

External links