How far is Mars from the Earth?

A common theme, particularly among American writers, is that of a Martian colony fighting for independence from Earth. It appeared already in the aforementioned Red Planet of Heinlein and is a major plot element in Greg Bear's Moving Mars, Kim Stanley Robinson's Mars trilogy, and S.C. Sykes' books. It is also part of the plot of the movie Total Recall and the television series Babylon 5. Many video games also use this concept, such as the Red Faction and Zone of the Enders series.