Last month we brought you a report about Blake Lively (Green Lantern) and Scarlett Johansson (Iron Man 2) eying the female lead role in Warner Bros.‘ sci-fi thriller Gravity. The film was written by Alfonso Cuaron (Children of Men) and his son Jonas.

Now, THR reports that Natalie Portman (Black Swan, THOR) has been offered the lead role, opposite Robert Downey Jr. (Due Date, Untitled Sherlock Holmes Sequel). Natalie Portman and Sandra Bullock were reportedly the two actresses that Warner Bros were most interested in.

Robert Downey Jr. is set to play the leader of a team posted at a space station. While he and a female colleague (possibly Portman) are traveling outside the space station, the other team members are decimated by debris from an exploded satellite. At one point, Angelina Jolie (Salt, The Tourist) was to play that female colleague opposite RDJ but has since passed on the project.

Gravity is slated to hit theaters in 2011.