Coding the red desert
Babylon 5 constantly pushed the envelope of computer-generated special effects, but the cost of creating a full futuristic Earth landscape -- complete with people, plants and other expensive organic shapes -- would have been prohibitive. While the series incorporated a few shots of Earthdome and other terrestrial locations, they were never particularly convincing.

Mars was a much easier environment to create. Since none of the show's fans have been to Mars, they're less likely to notice subtle mistakes.

The landscape is mostly rock and sky, which computer-generated images (CGI) simulate well.

Later episodes added cities, trains, and the occasional view of a dome's interior face, the geometric construction of a "Marsdome" simplified the graphics without sacrificing realism. Finally, Mars' inhospitable environment requires humans to stay indoors, justifying Straczynski's reliance on cramped but budget-saving interior sets.

Mars, then, was a godsend to a science fiction show with about half the production budget of its direct competitors in the Star Trek camp. However, there are also good story reasons why we saw more of Mars than Earth.

The next best thing to Earth
While not home, Mars is relatively close by galactic standards. Given the series' advanced transportation technology, travel time between Earth and Mars has narrowed to a few days at most.

This means the two worlds' politics and economies constantly interact, creating clear social issues and, eventually, making the frictions underlying the Free Mars revolution easy to explain to viewers.

The split between Mars and Earth also creates a perfect image for the fractured Earth Alliance -- two worlds near each other in space but divided by a gulf of issues. We're familiar with Mars and so we care about a Mars-Earth conflict more than we would care about an conflict between Earth and some nameless colony world around another star.

At the same time, Mars is far enough removed from Earth to keep some other crucial plot developments on track. This is most noticeable late in the series' run, when first Garibaldi and then Sheridan make the trip to the Red Planet.

The plot demands they enter the lion's den -- the fourth season of Babylon 5 is largely about going home -- but it would require ridiculous plot devices to sneak the characters past all of Earth's defenses and border controls.

Mars, on the other hand, is a disorderly enough frontier that viewers can imagine Sheridan and Garibaldi sneaking in without straining their suspension of disbelief past the breaking point. It's close enough to Earth to make the journey meaningful, but wild enough that the authorities' surveillance is relatively relaxed.

The hiding place
This frontier quality is closely linked to the final dramatic role Mars plays in the series.

Mars is mysterious, a planet with roughly the same surface area as Earth and only a tiny fraction of the population. All sorts of unknowns hide on Mars in Babylon 5, from Shadow ships to secret Psi Corp bases.

It's no accident William Edgars -- the blandly menacing embodiment of the series' totalitarian concerns -- lives on Mars.

Edgars is the forgettable villain, the monster with the face of Everyman, and so his martian residence makes sense. Not only does it make it much easier for Mr. Garibaldi to visit him, but the virus he's cooking up in his labs is yet another of the red world's secrets.

Even Jeffrey Sinclair, the character whose unknown importance and missing memories drove the show's early episodes, becomes a bit more mysterious by being born on Mars, halfway between Earth and alien space.

The future of Mars
Needless to say, it may be a while before we see another television show that treats the Red Planet in this level of cultural and political detail.

James Cameron's upcoming Mars miniseries, for instance, seem more focused on the trials of getting to Mars than living there, and there's not much else on the horizon.