A free-use world where mankind has expanded beyond Earth into the Inner Solar System. No aliens...yet. I might add some.

Here's a rundown of the Inner Solar System:

Mercury - Penal Mining Colony.

Venus - Terraformed into a second Earth.

Earth - Self-explanatory.

The Moon (sometimes called Luna) - First colony & spaceport

Mars - Humans in dome cities while the planet is being terraformed.

The Asteroid Belt - Asteroid mining.