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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".[citation needed] 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.[citation needed] As a purely molecular machinery, uses ionizing radiation as an energy source, its growth significantly accelerates if it is exposed to high doses and depends only on the abundance of such energy.

Extrasolar origins

It was initially believed by Protogen's scientists that Phoebe test was intended as a weapon research. However, The Investigator Books • TV informs James Holden Books • TV that it functions as an advanced terraforming platform.[citation needed] Final development in Sol system as the interstellar cross gateway however, is a proof of it's being programmed molecular device with a superior hard-coded prime directive to establish a galactic-wide transport network between targeted star systems with habitable planets.

The Protomolecule was created by extra-terrestrials around two billion years in the past, and launched as one of the Bracewell probe swarm at trajectories towards the stars harbouring planetary systems having conditions for the emergence and evolution of some molecular replication mechanism.[citation needed] Such replicators could be powered by energy from chemical bonds, such as life based on carbon, silicon or other elements, and also by any kind of photons or even radioactivity.[citation needed]

So, it looks like the protomolecule was a kind of comprehensive, adaptive, self-reprogramming (loaded with the basic code, able to expand this code, comprehensively adapt such extension and even reprogram it [citation needed]). In its primordial form, protomolecule was the idle, dormant agent being activated when a replication mechanism was encountered. Then, very similar to stem cells, protomolecule began to use this replicator to grow, alter and adapt itself according to hard-coded prime directive. When activated, the protomolecule carries out the programmed directive, using any material-animate (e.g. Eros' biomass) as well as inanimate (e.g. Eros' rock and the surface of Venus) and energy. By absorbing living matter, the protomolecule, however, does not build consciousness or collective consciousness (of human or other origin). Absorbed individual consciousness becomes autonomous subprocesses of artificial extraterrestrial intelligence, but not consciousness.

The protomolecule samples sent to the stars were like panspermia-like molecular phage, invented and developed for massive galaxy exploration. Like the phages we know from life on Earth, this protomolecular could only become active when it came into contact with the replication mechanism. Protomolecule was not programmed to develop life, however. It was the versatile molecular robot to develop interstellar communication system for life, instead.[citation needed]

One of those star systems targeted by protomolecule probes apparently was the Sol system, probably goldilocks zone trio of Venus-Earth-Mars[Citation needed] of which at least one planet had developed young primitive life at the time. Unfortunately, protomolecule seeding probe had been captured and trapped by Saturn's gravity, where it became a satellite, and settled there as one of its moons.

At some point between Bracewell probe swarm launch and the present day, the civilization that invented and then launched 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 XTEMCR 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 protomolecular experiment developed as a initial identify 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.

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

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 in a flash crew members on both Scopuli and Anubis, but not to Julie trapped right 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

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.[1]

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[2]. 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.

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.



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.

The stolen samples

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 stolen by the Laconian Empire 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.

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[citation needed], 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.[citation needed] 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[citation needed], 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.


  • infected Eros
  • infected Eros
  • infected Eros
  • The Protomolecule rises from Venus


  1. The Expanse Novella The Vital Abyss
  2. The Expanse Novel Caliban's War - Chapter 1: Bobbie

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