Actress Sigourney Weaver has just been cast in James Cameron's upcoming 3-D adventure "Avatar," reports Variety. The film reunites the pair, who first made a huge splash with the "Alien" franchise nearly thirty years ago. The name of Weaver's character has not yet been announced, though she is to play an experienced interplanetary explorer who acts as mentor to the lead, Jake Sully (as played by Sam Worthington).

"Avatar" tells a familiar story in science fiction terms.

Sully is a jaded ex-Marine used by his government to explore and exploit a planet rich in biodiversity, who eventually joins forces with the natives to save the planet. Zoe Saldana plays Neytiri, who will almost certainly be the wise-yet-mysterious-yet-spunky alien woman who helps change his allegiance and start the repair of his wounded heart. If this plot sounds familiar, it is, though Cameron has never let stock plots stand in the way of giving good spectacle. Joel David Moore, Peter Mensah, Laz Alonso, Wes Studi and genre favorite CCH Pounder are also joining the cast.

Cameron intends for the film to be shot entirely in 3-D, with 2-D and 3-D releases planned. Principal photography begins this April, with a planned release date of 2009.