Swords of Mars: The Solar System

The campaign setting assumes that interplanetary travel exists, but that interstellar travel does not. The solar system is a populated system, with hints of ancient terraforming and seeding of humanity across at least three worlds in a distant past.

A Brief History
The people of Old Terra nearly destroyed themselves in war and economic ruin; but over time they rebuilt their world under the leadership of the Imperium, and then reached out into space. As they traveled, they found that humans were not alone in the system, encountering the human and non-human races of Venus, Mars, and the Jovian moons. Early encounters on Venus led to protracted war, but now the solar system is at peace. Terra grows fat on the resources of the solar system, and has begun looking for places to house its people, living in crowded cities across the globe.

The 9 Planets & Asteroid Belt

• MERCURY is tidally locked to the sun, one side perpetually superheated, the other perpetually dark and cold. Life exists along the twilight band between hemispheres; a perpetually half-lighted, arid and rocky landscape populated by reptiles and small, furry, primitive humanoids. A handful of Terran mining colonies dot the twilight band.
• VENUS is a cloudy world covered with shallow seas, vast marshes, and thick jungles. It is populated by huge arthropods, dinosaurs, lizardmen, and pale-skinned, pale-haired humans who share an ancestry with Terran and Martian humans. Both Venusian species fought a protracted war with Terran invaders before settling into an uneasy peace.
• TERRA is home to the Imperium and the Terran Trading Corporation. Crowded, technologically advanced, and given to a sense of Imperial largesse toward the other worlds, Terra is not always welcomed in the Solar System.
• MARS is an ancient world which has gone through several periods before sliding into decline. The world is now arid and dying, most of its cities ruins, and the civilized Canal States are falling into decline. The Terran Trade Corporation is active here, with little Imperial interference.
• The ASTEROID BELT is a lawless region, home to space pirates, pleasure worlds, and free miners. Once it was an ancient planet— even compared to Mars— ruled by masters of science and magic, but it was destroyed in a great catastrophe, and only echoes of their past still exist.
• JUPITER is a gas giant, utterly uninhabitable. Its four major moons, Callisto, Europa, Ganymede, Io, are cold but habitable worlds warmed by volcanic activity. Each are home to alien forests, animal life, and a variety of primitive intelligent life. Ganymede is the warmest of the four moons, covered with jungles and home to a species of blue-skinned humans who live on mesas that rise above the jungles. Terran colonies on these worlds exist mostly as bases for mining the smaller moons of Jupiter.
• SATURN, like Jupiter, is a gas giant. Terrans mine the ice of its rings and its cold moons for gasses, fuels, and water. The moons of saturn are lifeless.
• URANUS and Neptune are icy gas giants, generally deemed to distant to be worth mining for resources when closer planets offer similar resources.
• PLUTO is a rocky planet. Terran explorers have gone to Pluto twice and not returned. It is now a quarantined world. 

The Terran Trade Corporation
The Terran Trade Corporation, also known as the TTC or the Corp, is a latter-day interplanetary version of the East India Company. Their primary purpose is off-world trade, so TTC runs mining operations, import-export operations, and even smuggling of artifacts. They also trade in spices, rare fabrics like Venusian spider-silk, and other exotic goods. In pursuit of its Imperial monopolies, the TTC has a large security force and controls territories off-world, giving them a paramilitary presence and wide-ranging powers to protect their interests. The TTC has learned from entanglements on Venus to try subtlety, bribery, espionage and manipulation where it can, however.