It's the battle of the space vixens.

Blake Lively
and Scarlett Johansson are vying for the chance to star in the outer space thriller 'Gravity,' a Warner Bros. film co-written and directed by Alfonso Cuaron ('Children of Men'). Robert Downey Jr. is attached as the male lead.

According to HeatVision, 'Gravity' revolves around astronauts repairing the Hubble telescope who are hit with an avalanche of satellite junk; the surviving astronaut must fight her way back to Earth, where she hopes to reunite with her daughter. Johansson and Lively both have tested for the female astronaut role in the last few weeks. div style="text-align: center;">