Written by Mirrond

One of the four Galilean moons of Jupiter and the capital world of the Iron Pact. Wildly considered the nicest place to live within not just the Jupiter Subsystem but also entire Outer Solar System, at least if you somehow manage to ignore its government.

Geography

The best way to describe the Callisto's climate is 'eternal warm spring'. What's more, it is a dead object - there is no notable volcanic activity to speak off, resulting in large degree of tectonic stability (unlike, for example, Io).
It has been terraformed through partial Ground Insulation method, which means that while the icy surface layer of the planet was melted, the rest wasn't. As a result, it has a mixture of land and seas (not unlike Earth), with a massive number of lakes created within the old impact craters.

Ecosystem

Practically the entirety of Callisto has a climate roughly similar to the temperate regions of Earth. The problems its ecosystem faces, however, are rather significant. Not only is this world's gravity extremely low, the soil is also rather barren (not unlike that of Mars).
There are on-going attempts to alleviate the latter problem by mass soil enrichment programs. The former can't exactly be solved by such conventional means, though not for the lack of trying. Iron Pact is financing a number of gene-editing programs tasked with adapting a variety of species from the Earth's Europa to populate Callisto with, with some notable successes.
Thus far, most of the ecosystem - aside from things like moss, lichen, fungi and algae - are slightly more complex plants (grass, flowers, small bushes etc.) and small animals, such as birds and rodents.
Iron Pact plans to have trees and large animals (such as deers, foxes, wolves etc.) on Callisto by the end of the century, which might change Callisto's status from a Terran Eccentric world to a Terran one - if the Pact succeeds, that is.

Distance from Sun: 778.57 mil. km
Distance to Jupiter: 1.883 mil. km
Diameter: 4821 km
Solar Constant: 0.073
Mass: 0.018 Earths
Gravity: 0.126g
Mean density: 1.834 kg/l
Day Length: 16.689 Earth days
Year Length: 11.862 Earth years
Rotation Axial Tilt: <10 degrees
Avg. Temperature per Latitude
poles: 12 C
75 deg: 14 C
60 deg: 15 C
45 deg: 16 C
30 deg: 16 C
15 deg: 17 C
equator: 17 C

Astrography

Object Type: Icy Moon
Object Subtype: Terran Eccentric
Primary Location: Core Sector
Secondary Location: Solar System
Tertiary Location: Jupiter Subsystem
Transshipment Station: Himalia

Habitation Status

Status: Colonized
Classification: Civilized World
Population: ~23 mln.
Capital: Nouveau Paris
Government: Iron Pact
Solar Commonwealth Member: Yes.