Who will be cast as the hotter than hot female lead opposite suave Robert Downey Jr. in director Alfonso Cuarón’s upcoming space thriller Gravity? Inquiring brains want to know!

In one corner we have the new girl on the block, Blake Lively. She’s tall, leggy, luscious, and is currently heating things up on the Green Lantern set playing Ryan Reynolds’ main squeeze Carol Ferris. In addition, this sexy siren is still breaking hearts and bank accounts as wealthy Manhattan socialite Serena van der Woodsen on the small screen smash Gossip Girl.

In the other corner we have the cagey veteran, Scarlett Johansson. She’s short, curvy, bodacious, and is currently married to Mr. Green Lantern himself, Ryan Reynolds. In addition, this scintillating sexpot is riding high after her appearance in the summer smash Iron Man 2 where she played Natasha Romanova, aka Black Widow.

According to Heat Vision, both of these buxom blondes are engaged in an epic battle of hair-pulling and name-calling to earn the right to star alongside Downey. I made up the stuff about the hair-pulling and name-calling, but both actresses have apparently been tested and are rumored to be the leading candidates. Here’s a quick synopsis of the flick for those in the dark:

The movie’s plot revolves around astronauts repairing the Hubble telescope who are hit with an avalanche of satellite junk. In a plot akin to “Cast Away,” the surviving astronaut must fight her way back to Earth, where she hopes to reunite with her daughter.

Sounds like a meaty role. I think either chick could do it justice, although I’m leaning toward Blake in this titanic tussle. I like Scarlett and all, but I’d love to see how Lively performs with Cuarón behind the lens and Downey in front of it. I’m convinced she’s more than just another pretty face and seems poised for big screen stardom based on the parts she keeps landing.

Stay tuned for further updates about this casting conundrum.