Old Mars

The fourth planet of the Sol system and the site of humanity's first and best exercise in planetary terraforming. Now home to some 900 million and a highly successful and valued part of the the Earth Empire. The original inhabitants and terraformers of Mars, known as the Martian Helix formed the wave of colonists that settle New Mars, and ultimately formed the core of what is now the Martian Association of Free Colonies.

Free Mars

A few dissidents have for many years argued that the planet should be independent of Earth and the Solar Republic - and in the past there has been some unpleasantness over the issue. These days the 'Free Mars' movement exists as only a few minor criminal groups who continue to use the pretence of a legitimate claim for self-determination as a cover for acts of terrorism and theft, but these have little support form the vast majority of Martians, both on and off Old Mars.
However, the violent history of the 'Free Mars' movement includes revolutionary songs such as this one:

"It's a long way to the Mars homeworld,
It's a long way to go
It's a long way to the Mars homeworld,
To the sweetest orb I know,
Goodbye to Adobe,
Farewell to Myter,
It's a long long way to the Mars homeworld,
But my heart lies there." (1)

Which is still banned by the Earther authorities on Old Mars.

(1)Thanks to Serena for that one.