This week’s article was delayed for health reasons, but here it is. Part 1 covers planetary conditions and part 2 covers the inner solar system. This week we’re covering the outer solar system, which is really the cooler half with a lot more variety.

Atmosphere: Average
Gravity: Heavy
Radiation: Safe
Temperature: Temperate
Special: Corrosive Clouds, Floating Platforms, High Winds (18")

Jupiter’s severe gravity has long limited its trade and interactions with the wider solar system, but that has not cut those connections fully. Much like Venus, Jupiter saw the construction of gas harvesting platforms to collect Hydrogen, Helium, and Ammonia. Unlike Venus, those platforms tend to be autonomous and uninhabited. Worse, because of Jupiter’s radiation belts, no convenient orbits present themselves for O’Neill Cylinders. Instead, anyone working on Jupiter lives on the Jovian moons. 

Jupiter’s industrial platforms rest just above the Ammonia clouds, with collection systems hanging down into that layer. The platforms themselves use Helium-3 collected from the atmosphere to power a fusion reactor that provides the necessary thrust to keep the platform afloat. Those same platforms accumulate Ammonia for export to agridomes throughout the system. 

Conflicts for control of these floating fusion plants are known to happen despite the extremely dangerous conditions produced by Jupiter’s gravity. Forces willing to risk the gravity are wise not to do so for more than a single day of operations.

Orbital Stockpiles (Mass Driver): Jupiter’s mass driver satellite arrays are normally used to send cargo or energy to inner planets, but they can also crush an invading force easily enough.

Top-End Hardware (Jump Jets): Necessary to navigate platforms safely.

Atmosphere: Insubstantial
Gravity: Very Low
Radiation: Extreme
Temperature: Cold
Special: Lava, Lightning, Precipitation (Ash, Snow), Quakes

Unique throughout the solar system, Io is a radioactive hellscape coated with ice fields and lava flows. Lightning strikes between sulfur dioxide snow and volcanic ash. No one lives on Io, not for long anyway. But what Io does have is the single largest power reactor in the solar system. 

Prior to the construction of the Dyson Swarm, the Jovian colonization program constructed conductors on the poles of Io, connected by 11,500 km of infrastructure. This system generates 1.2 million megawatts of power which it distributes to the moons of Jupiter. 

Because of the extreme radiation present on Io, only a minimal crew of soldiers and mechanics are present on Io at any given time, bunking in extremely shielded outposts and piloting HE-Vs to do maintenance and defensive operations. 

Local Garrison (UL HE-V): A dedicated squadron of maintenance Ultra-Light HE-Vs is rarely far from any point along Io’s infrastructure.

Elite Pilot Program: The Io Engineers’ Corps has some of the most experienced pilots in the system with years of experience operating HE-Vs to perform repairs in the most hostile environment imaginable. 

Atmosphere: Insubstantial
Gravity: Very Low
Radiation: Hazardous
Temperature: Cold / Extreme Cold
Special: Meteor Showers

The radiation and paucity of raw materials on Ganymede prevented it from ever being developed as much as other moons, but it does house a number of scientific outposts studying the ecosystem of Ganymede’s subsurface ocean. These outposts have become a sometimes exploited vulnerability of the Jovian system. 

Daring military commanders sometimes seize control of Ganymede’s spaceports to set ambushes for the moon’s occasional supply ships. Once captured, they make great Trojan horses to infiltrate other moons in the system. 

Local Garrison (Support): Ganymede’s outposts often trade supplies using support vehicles traveling over the surface to avoid disrupting the underwater habitats they’re researching.

Adv. Hardpoint Design (Tracked): Ganymede’s has a very rough surface lacking in obstructive terrain, so their HE-Vs were built with heavy tracks to overcome it.

Atmosphere: Insubstantial
Gravity: Very Low
Radiation: Very Hazardous
Temperature: Extreme Cold
Special: Meteor Showers, Quakes

Many of the same negatives that hindered Ganymede’s colonization also limited Europa’s, but unlike Ganymede a rich and thriving ecosystem was discovered under Europa’s ice. Once discovered, and found to be fully compatible with human physiology, fishing and agriculture colonies developed under the ice away from the radiation and produced much of the food consumed in the Jovian gravity well.

Conflicts on the surface of Europa often break out over control of the supply lines from these colonies to their space ports. Anyone attempting to siege Jupiter’s moons would need to control Europa to limit supplies to the other moons. 

Exhaustive Intel Gathering: The surface of Europa is covered with surveillance devices to provide an early warning system against any threat to the Jovian system’s main food supply.

Network Hackers: Because of Europa’s high surveillance society, many children learn to hack colony security grids early in life and develop it into a skill by their teenage years. Some develop this into a professional skill by adulthood. 

Atmosphere: Insubstantial
Gravity: Very Low
Radiation: Safe
Temperature: Cold
Special: Meteor Showers

The largest population center beyond the asteroid belt, Callisto was the first of Jupiter’s moons to be colonized and the launch point for all colonization and mining operations in Jupiter’s orbit. 

As the outermost of the Galilean moons, Callisto became a hub of industry and manufacturing by receiving energy beamed from Io and resources mined from the outer moons. Callisto’s shipyard is the only one of its kind in the outer planets, control of which has been contested before by powers seeking to expand their influence to Jupiter and beyond.

Materiel Stockpiles: As one of the main shipyards, Callisto is able to build armor and structure components far more efficiently than most worlds.

Adv. Hardpoint Design (Multi-Limbed): Callisto’s very rough and cratered surface dramatically slows surface navigation. Callistans turned this into an advantage, building their HE-Vs with spider-like limbs to allow them to hunker down behind cover wherever it could be found.

Atmosphere: Average
Gravity: Normal
Radiation: Safe
Temperature: Cold
Special: Floating Platforms, Extreme Winds (8")

Floating cities built around fusion reactors like those found around Jupiter rest 100km deep into Saturn’s atmosphere. Although dependent on heating and insulation to maintain a habitable environment, Saturn’s lower gravity means a lower percentage of the reactor’s power need be spent on thrust. 

Other than that, Saturnian habitats have little benefit and are few and far between. Their main value is as control stations managing orbital railguns selling kinetic energy to Jupiter and the inner planets. They also harvest gases and fuel for ships traveling to the Kuiper Belt.

Orbital Stockpiles (Mass Driver): Saturn’s mass driver satellite arrays are normally used to send cargo or energy to inner planets, but they can also crush an invading force easily enough.

Top-End Hardware (Jump Jets): Necessary to navigate platforms safely.

Atmosphere: Thick
Gravity: Very Low
Radiation: Safe
Temp.: Extreme Cold
Special: Precipitation, , Unstable Terrain (porous ice)

Titan is the largest colony world beyond the Jovian system, but also one of the most unpleasant. The surface suffers from extreme cold, having liquid ethane and methane lakes, a full weather cycle, a thick atmosphere, dim light, storms, and gross snow-like sludge falling from the sky. Unstable ammonia ice coats the surface, and vicious dust storms accrete sand dunes along the world’s equator.

Evading the planet’s extreme temperatures and weather required the colonists to burrow underground for insulation. Many of the older and more established colonies have invested in underground tunnels connecting each other for trade and transit, meaning many of Titan’s colonists haven’t even seen, or have only rarely seen, the surface. This has lead to many superstitions and rumors to form about the planet the live on. Most notoriously, and difficult to discourage, is the legend of the Titan Yeti.

The abysmal visibility, extreme cold, and alien atmospheric conditions have given many people bizarre experiences, sights, and sounds that they cannot explain. The scientific answer that’s given over and over is a combination of weird interactions between atmospheric gases existing at temperatures people just aren’t used to. These can create odd whistling or howling sounds, and combined with mirages caused by petrochemical clouds interacting with methane lakes allegedly explain the Yeti sightings.

Orbital Stockpiles (Mine Drone Barrage): Titan manufactures mining charges used on Saturn’s other moons, and can quickly turn those into IEDs.

Adv. Hardpoint Design (Reactive Armor): Given the increased risk of blast weapons in Titan’s thick atmosphere, HE-Vs built here make use of specialist armor to manage risk

Atmosphere: Average
Gravity: Normal
Radiation: Safe
Temperature: Extreme Cold
Special: Corrosive Clouds, Floating Platforms, High Winds (18")

Similar to Jupiter and Saturn, Uranus supports floating cities and atmospheric mining platforms. However, due to its much lower temperature, Uranus’s cities are able to rely on buoyant lift from heated helium gas rather than fusion-powered propulsion. Because of this, its platforms more resemble those around Venus and are carried on the winds.

Initially built as part of an intrasolar infrastructure program made possible by the limitless power of the Dyson Swarm, Uranus’s platforms were ill-conceived and provided limited benefit beyond their scientific and gas mining functions. The platforms keep only a minimal population with most of the inhabitants of Uranus’s gravity well occupying equally resource-deprived colonies in orbit or on Uranus’s myriad moons.

Uranian habitats more closely resemble colonies of the Asteroid Belt than they do colonies anywhere else in the solar system, save for their inability to harness solar power. When the Dyson Swarm failed, colonists of Uranus were forced to repurpose the mass drivers of their lunar shipping system into an improvised kinetic impactor generator system. Uranus remains one of the poorest regions of the system.

Outrageous Support (Mass Driver): Colonists of Uranus’s various moons can retask their generator system for limited kinetic strikes.

Top-End Hardware (Jump Jets): Necessary to navigate platforms safely.

Atmosphere: Average
Gravity: Normal
Radiation: Safe
Temperature: Extreme Cold
Special: Corrosive Clouds, Floating Platforms, Very High Winds (12")

The gas extraction platforms of Neptune are the least efficient in the entire solar system. Neptune’s slightly above average gravity and miserable environmental conditions make it some of the most costly to extract. The facilities were built shortly after those on Uranus under the same infrastructure initiative with the intent that future expeditions to the Kuiper Belt could use Neptune as a resupply point and base camp. These plans all depended upon the transmission of the Dyson Swarm’s readily available free energy.

After the collapse, nearly all trade and transit to the Kuiper Belt ended. Neptune’s wealth dried up and it became the poorest gravity well in the system. Desperate prospectors strike out into the Kuiper Belt seeking rare or unique prizes. Every one of Neptune’s rock-hoppers hopes to find an extrasolar object to sell to one of the corporations or universities further sunward. Such prizes are rare, but not unheard of. And well worth fighting over.

Local Garrison (LAS-Wing): LAS-Wings can scramble from nearly every platform on Neptune, and those that don’t have their own can call for one from a neighboring platform.

Top-End Hardware (Jump Jets): Necessary to navigate platforms safely.

Atmosphere: Insubstantial
Gravity: Very Low
Radiation: Safe
Temperature: Extreme Cold
Special: Meteor Showers, Quakes

A captured trans-Neptunian dwarf planet, the surface of Triton is one of the coldest in the system but also one of the most active. When the first colonists arrived on Triton, they expected a dead world with a long-frozen sub-surface ocean. They were in for a shock.

Far from being frozen, Triton’s ocean was warm and full of bizarre life. At some point in the dwarf planet’s distant past, an extrasolar object containing a massive quantity of radioactive material collided with the moon and pushed it out of the Kuiper Belt into Neptune’s orbit. 

The radioactive meteor penetrated the ice, sunk through the planet’s ocean, and scattered to cover the sea floor. The heat of the impact and continuing heat of radioactive decay kept the ocean liquid and provided a basis for life to develop. Radiotrophic growths covered the depths, and began an entire food chain. Without the fisheries and undersea farms of Triton, Neptunian colonists couldn’t afford food.

The nature of the meteor remains a mystery, and the inspiration for Neptunian treasure hunters to scour the Kuiper Belt. Rumors persist among Triton’s ice fishers and submariners that it was an alien ship. What few tourists Triton receives are often sold counterfeit alien artifacts. 

Intimidation Tactics: Triton’s defenders love to use the rumors of aliens to unsettle invaders.

Advanced Structural Components: The original HE-Vs sent to Triton were built to operate where spare parts were few and far between, and those units remain in service today.

If you couldn’t tell, Titan and Triton were my favorite moons to make stuff up for. Given how many of these moons have under ice oceans, I am thinking about writing up some rules for underwater combat encounters. But I felt that could have been a whole separate article.

Many thanks to the Tough SF blog for being a tremendous resource in my research. Really great articles all around.

The Intrasolar Operations banner uses the following image:

Image title: As iau0601a but without annotations.
Credit/Provider: The International Astronomical Union/Martin Kornmesser
Short title: The new Solar System? [unannotated]
Date and time of data generation: 16:22, 16 August 2006