There are two solar systems – NASA’s and Hollywood’s – and the twain don’t always meet. NASA would like to send humans to Mars, if Congress would bankroll the mission. But Hollywood filmmakers have sent humans to Mars for decades, ever since Buster Crabbe piloted giant Roman candles across the cosmos of Depression-era America. More recently, new digital technologies have allowed movie-makers to depict extraordinarily realistic-looking Mars flights. Digitally realized space odysseys include last winter’s “Mission to Mars” and the forthcoming 50-odd-million-dollar “Red Planet,” plus the recent orbital comedy-drama “Space Cowboys.”