This from AICN...
* Dominic West, who played Baltimore cop Jimmy McNulty on five seasons of “The Wire,”(as well as Jigsaw in Punisher Warzone) will play Sab Than, the Martian prince who in the books tried to force the fabulous red Martian princess Dejah Thoris to marry him.
* Samantha Morton, psychic-girl Agatha in “Minority Report,” will play Sola, the 10-foot-tall four-armed green secret daughter of Martian warrior Tars Tarkas. In the books she instructed Carter in Martian language and culture.
* Polly Walker, a secret human monotheist in Syfy's "Caprica" and Octavian’s mom Atia on both seasons of HBO’s “Rome,” will play Sarkoja, the old green martian chieftan who in the books killed Sola’s mom long before Carter’s arrival.
They join Taylor Kitsch (“Wolverine”), Lynn Collins (“Wolverine”) and Willem Dafoe (“Spider-Man”), who play John, Dejah and Tars, respectively. The movie is scheduled to hit cinemas in 2012. Writer-director Andrew Stanton (“Finding Nemo,” “WALL-E”) makes his live-action directorial debut from a screenplay by Stanton and Michael Chabon (“Wonder Boys,” “Spider-Man 2”).
This cast is looking good! I'm not too familiar with Walker out side of a few scenes in the Caprica pilot, but West and Morton are great..if you don't count that silly performance in Warzone!