Msn has debuted an all-new video clip from James Cameron's upcoming sci-fi epic Avatar. Here, Parker Selfridge (Giovanni Ribisi) explains the purpose behind Jake's (Sam Worthington) mission to Grace (Sigourney Weaver). To watch the scene, click on the video below:In the future, Jake, a paraplegic war veteran is brought to another planet, Pandora, which is inhabited by the Na'vi, a humanoid race with their own language and culture. Those from Earth find themselves at odds with each other and the local culture. Directed by James Cameron and starring Sam Worthington, Zoe Saldana, Sigourney Weaver, Michelle Rodriguez, Giovanni Ribisi, Joel David Moore, CCH Pounder, Peter Mensah, Laz Alonso, Wes Studi, Stephen Lang, and Matt Gerald, Avatar opens December 18th, 2009.