The colonization of the outer solar system was, in contrast to that of the inner solar system, a haphazard and disorganized affair. It occurred in fits and starts, beginning shortly after the colonization of Mars, but failing to pick up steam until the closing decades of the 21st century.
Reaching the moons of Jupiter and Saturn was a very different sort of task than getting things into space in the first place had been. In some ways, it was harder, but in others, it was much easier. Once a significant population existed in space, and space manufacturing began to accelerate in orbit of Earth and Mars, the prospect of sending a mission to Europa began to look no more difficult than sending a mission to perform asteroid prospecting.
It took until 2044 for a human to see Jupiter with their own eyes, instead of through a telescope or screen. A series of long-duration scientific outposts established by the various member states of the UN were the first tentative steps into the realms of the gas giants, and during the Martian War of Independence, those outposts remained humanity’s only foothold in the outer system.
At the close of the war, that began to change. A combination of Martian expatriates who wanted no part in the new Martian government, and corporations who found themselves disadvantaged by the new trade laws existing between Earth and Mars, set their sights on the virgin territory of the gas giants and their vast systems of moons and rings.
Some of those early colonies did very well for themselves. What began on Europa as a ramshackle collection of stolen Martian pressure domes, optimistically named Annwn City, slowly grew in power and influence into the Europan Republic. On Triton, Sociology Professor Soto Ishihara completed his manifesto, The Engines of Liberty, and founded the Open Sky Movement. The discovery of simple hydrocarbon-based life on the shores of Titan’s Kraken Mare drove a minor flurry of scientific research as dozens of independent research outposts went up on the shores of Titan’s alien seas.
However, not all of these endeavors faired so well. The distances to the outer planets were great in those days, and disaster befell many of the more ill-conceived or poorly funded attempts to establish settlements long before they ever reached their destinations. Of those that made it, many failed to take hold, underwent minor local revolutions, and even turned to piracy as their ventures failed.
Earth and Mars both tried their hands at policing the outer system, but the distances made even their vessels ill-suited to the task, leaving military forces chasing stories of ghosts, any raiders long gone before the navy could get anywhere near them.
In response to the perceived inability of the inner planets to maintain order, many of the more successful colonies and outposts funded the creation of their own local security forces, whose services they sold to their neighbors. After a series of short but brutal conflicts between the Europan Security Service and the Ganymedean Guard over mining rights on Io, these groups and other various other locally involved security organizations signed the Tartarus Accords in 2179.
The Tartarus Accords began as nothing but a series of legal precedents and jurisdictional and judicial rules of thumb that the various security forces agreed to follow to prevent conflict between them. Over the following decades, they would grow into something far larger than their creators had ever envisioned.
In 2088, fusion propulsion breakthroughs allowed for highly efficient thruster designs that had previously been only theoretical at best. Ships began being constructed that could perform 1 gee burns for months at a time, and the entire design philosophy behind starship construction reeled from that new fact.
These breakthroughs also lead to a flood of new colonization projects in the outer system, and a renewed interest among the governments of the inner planets to secure their holdings and exert influence over what they saw as ultimately their domains. Many smaller colonies found themselves under the thumb of the inner planets and began to call upon local security forces to enforce their independence.
This trend among smaller colonies began as merely a legal dispute in the early 2090s, but by the turn of the century, the situation had grown increasingly hostile on both sides. As the Tartarus Accords gained more and more of a mantle of authority in the outer planets, a conflict began to brew between the signatories of the Accords and the nations of the inner planets.
The situation finally reached a boiling point in 2101, when an Earth-owned corporation’s mine broke through into an independent colony on Callisto and killed several hundred people when an underground housing block depressurized.
Europan Security Service forces secured the mine on behalf of the Callistean colony, leading to the outbreak of armed conflict, as UN forces working on behalf of the mining corporation tried to secure the holding.
The conflict quickly escalated onto the orbital planes, as the UN declared the Europans’ security force in violation of interplanetary law and began listing them an outlaw organization. In response, UN vessels were labeled as pirates by the Tartarus Accord, and the wheels of war began to spin faster and faster. Battles between UN and Tartaran starships peppered the space lanes, as the two factions did battle over the immense distances of interplanetary space.
Mars initially attempted to remain neutral in the informal war, but their internal policy of failing to respect the legal standing of the Tartarus Accords quickly drew them into the brewing conflict. When the Titan Independent League negotiated through the Accords to annex all independent outposts left on Titan’s surface, Mars insisted that this policy simply would not apply to their outposts, and any such attempt to assert influence over them would constitute a declaration of war. When the Accord called Mars’ bluff, the reluctant Martians were forced to either enter the war or risk losing their holdings.
The Gravity War began as the barest trickle of a conflict, with UN forces boarding corporate-owned vessels to assert dominance and being met with intense room to room fighting. Tartaran security vessels strategically targeted UN military ships for destruction, and interdictions and raids on shipping lines by one side or another made up the bulk of the fighting, but as the war ground onwards, the conflict began to escalate.
More and more Martian and UN military assets were directed at the problem of subduing the rebellious outer system, pushing the outer planets into an impossible race to keep up with the inner planets’ production abilities.
As a seemingly endless tide of naval ships began climbing the gravity well towards the outer planets, the Accords grew bolder and more desperate. The Tartarans had distance working in their favor, along with the orbital high ground, and they had a few tricks up their sleeves.
Back during the 2070s, the nationstates of the nascent Accords had begun constructing a large system of momentum exchange tethers in orbit of the various gas giants. Combined with gravity assists from the interactions of all the various moons, the system was designed to cut the fuel costs for even shipping between the planets down to almost nothing. As the system grew over the decades, its ability to handle increasingly large cargo at an increasingly rapid rate helped drive the development of Tartaran industry, and by the time of the Gravity War, the Tartarans had turned it into something of an art.
Faced with the possibility of oppression at the hands of Earth and Mars, they turned it into a weapon. The system of massed tethers became known as the Hecatoncheires, the hundred armed giants of Greek legend. In the autumn of 2107, the Hecatoncheires began throwing rocks.
This was not a subtle act, and the Tartarans knew it. They had escalated in a massive way. The system flung chunks of rock and ice kilometers long into orbits that would intercept Earth and Mars in a few years, at a rate of just over thirty per day.
The governments of Earth and Mars reeled as military forces were pushed into reacting, put on the back foot as they were forced to dedicate significant resources to diverting the asteroids off course. Hidden caches of attack drones stashed aboard the asteroids made the task even more of a resource drain, costing the inner planets ships and lives to keep the stream of world ending rocks at bay.
It took several years for the UN and Martian militaries to recover enough momentum to strike back against the Accords, and in the spring of 2109 a large combined UN/Martian fleet entered the Jovian sphere of influence, intent on bring the war to a close and silencing the stream of rocks being hurled at their worlds.
The Tartarans had long anticipated this event, and they knew they would not be able to match the inner world’s production levels for decades, maybe centuries, and so they employed a different strategy.
The orbital planes of the Jovian moons were strewn with mines and boobytraps. Bases were abandoned and programmed to self destruct upon a tripwire in the command center going off. Tethers quietly swung Tartaran assets around without firing thrusters, lobbing ships and ordnance in amidst the inner planets’ military forces, spreading disorder and chaos.
The inner planets’ fleet rampaged nearly unchecked through the Jovian system, but their actions were nearly futile: it seemed no matter how many tethers they destroyed, still, the rocks continued to fly.
As the death toll continued to climb in the inner planet fleet, they began to grow more aggressive and vindictive, and in the autumn of 2109, the fleet took up orbit of Callisto and threatened to destroy every installation on the moon unless the Accords surrendered.
The colony on Callisto quickly sent back a radio transmission, just three words, “Go fuck yourselves.”
Hundreds of nuclear missiles were launched from Callistean colonies and installations at the UN/Martian fleet, even as the inner planets’ fleet began their own systematic nuclear bombardment of the world. Military assets, gunned up merchants, and assorted pirates and rogues all piled onto the inners’ fleet as they laid siege to Callisto. The death toll was staggering on both sides, but in the end, the majority of the UN/Martian fleet was left scattered and in retreat, at the cost of nearly half the population of Callisto.
In the summer of 2111, two small asteroids made it through the Martian screen and struck the surface of Mars, resulting in mass death and destruction on the surface and blowing a huge amount of debris back out into orbit.
The war continued to simmer and rage throughout the asteroid belt as inner and outer planet forces clashed around asteroids and along trade routes, but after another failed incursion at Saturn in 2113, the steam began to go out of the inner planets’ fleets.
The Gravity War had raged for over a decade now, and for over half of that time, the people of Earth and Mars had been living with the threat of annihilation looming over their heads. Everyone was sick of conflict. The last fleet action between Tartaran and inner planet vessels occurred in December of 2114, after which the war simmered for another six months, with the inner worlds’ still having to play catch with all of the asteroids.
Finally, in June of 2115, a new peace treaty was signed between the Tartarus Accords, the UN, and Mars, bringing the Gravity War to a close. It would take nearly a decade after the war’s end to divert all the asteroids that had been aimed at the inner planets.