The Sun is the Solar System’s only star. It is a type G star, currently in its stable phase. It is only halfway through it’s lifespan, and will not become a red giant star for another five billion years; however, changes in it’s luminosity will have catastrophic consequences for life in the Solar System billions of years before it becomes a red giant. Currently, the Sun belongs to the Martian Union, who harvest its energy using a dyson sphere.
Mercury is a small rocky planet, closest to the Sun. It used to be the size of Mars, but has had much of its mass mined out in order to construct the Sun’s dyson sphere. Today, it is home to several small observatories that monitor the Sun, uninhabited except when maintenance needs to be done.
Venus is a rocky planet, roughly the size of Earth. A runaway greenhouse effect has left it a boiling, sulfuric hellscape. In the 24th century, plans were written up for it to be terraformed, but these were abandoned when exotic microorganisms were discovered floating in its atmosphere. To this day, no person has ever set foot on Venus.
Earth is a rocky planet with naturally occurring life. It has a notably large moon for its size which probably formed in a very unusual way. It is home to three groups of notable lifeforms; Earth plants, green plants, arthropods, invertebrates with an exoskeleton, and tetrapods, animals with an internal skeleton and usually four limbs. From the tetrapod lineage has come a sapient species known as humans. Earth is legally owned by the Martian Union, but the tribal societies inhabiting Earth today govern themselves. Both the MU and Earth’s peoples collaborate to keep the planet as a protected region for the sake of it’s native lifeforms.
Mars is a once-barren, now terraformed planet inhabited by the humans and other sapients of the Martian Union. Once freezing and covered in red desert, it has since been terraformed by humans and is now warm and lush. It is oft known as the home of humanity, and is the most politically important inhabited planet in the Solar System.
The Outer Solar System (OSS) is a collective name for the geography and nations of any part of the Solar System found further from the Sun than Mars’ orbit. This includes the inner and outer asteroid belt, the planets Jupiter, Saturn, Neptune, Uranus, and Orcus, and thousands of distinct nations, usually small, living within space station cities, habitation rings, or the like. These nations are usually descended from resource-gathering colonies or science outposts who at some point declared independence from nations like the UHALE or Martian Union. Most have populations below 500,000 people, though a few break one million in number. Like the animals on island ecosystems often being some of the most bizzare, the OSS is home to the strangest nations in the Solar System
The inner asteroid belt (more casually known as Jupiter’s spoils) is a ring of metal-rich asteroids that provide the majority of the Solar System’s metal and mineral resources. Every large nation in the system has some kind of claim over a group of asteroids. Despite the billions of tonnes of ore mined each year for several hundred years, less than 1% of the available resources have been used up.
The inner asteroid belt also contains one dwarf planet, Ceres. Political debate exists over whether Ceres should be mined, or whether it should be protected in case life exists there. However, tension between nations has prevented any expeditions from going there and proving or disproving the existence of life on Ceres.
Jupiter is the largest planet in the Solar System; a gas giant with more than 80 moons. Also orbiting Jupiter are 80% of the nations in the Outer Solar System, whether they be habitation rings, space station cities, or other artificial structures, as well as many science outposts. Though it doesn’t have a surface to live on, Jupiter technically has a population of over fourteen million people.
Besides Earth, Jupiter’s moon Europa has the most fascinating and diverse natural ecosystem in the Solar System. Various expeditions and research stations have discovered thousands of species, but new ones are being discovered all the time. Europa is now protected by the Martian Union, after it somewhat controversially claimed the moon from Jupiter’s largest nation.
Saturn is a gas giant with more than 80 moons, as well as the largest and most elaborate ring system in the Solar System. This makes it a very popular tourist destination. Thus, many of the Saturnian nations- about 17% of the nations in the OSS- make most of their money off of tourism. Saturn is home to a little less than two million people.
Saturn has not one, but two moons that contain life- Titan and Enceladus. Various machine expeditions have been launched to Titan to research the life there, though no humans have ever been to its surface. Enceladus has only ever seen enough visits to confirm that it does have life. Titan’s lifeforms are mainly small, chemosynthetic moss-like mats, and Enceladus’ life are microbial in nature, so considering that life more exciting to the general public can easily be found elsewhere, scientists struggle to get funds to send expeditions to these moons.
Uranus is an ice giant with more than 30 moons. It’s home to less than 1% of the nations in the OSS, which barely get any contact with outsiders beyond trade.
Neptune is an ice giant with about 20 moons. Aside from being home to about 3% of the nations in the OSS, it is extremely important economically to the nations of the Solar System for its established infrastructure in gathering resources like helium and hydrogen and sending them elsewhere. Who owns which parts of Neptune is hotly debated.
The Kuiper belt is a second, outer asteroid belt. It contains more resources than the inner asteroid belt, but isn’t mined nearly as much by the nations of the Solar System. It is of note for containing a large number of dwarf planets, like Pluto and Eris.
Orcus is a planet known to exist mostly by its gravitational impact on the orbits of hundreds of known asteroids. A rough orbit is known, and a few blurry photos have been taken by distant satellites. However, no expedition has ever gotten close enough to take a clear photo or land on its surface. Eleven separate expeditions sent to Orcus, three of them manned, have all disappeared before they got close to the planet. This has led to the common superstition that Orcus is cursed, which has of course further discouraged sailors from trying to travel there.