Comic books have done Robert Downey Jr well, so he’s going back to their inky pages for another project – this time he’ll be playing a gunslinger in an adaptation of the comic Cowboys & Aliens. The premise is exactly what it sounds like – an alien spacecraft arrives in the middle of a battle between Old West settlers and Apaches. The two warring factions have to get together to fight off an alien invasion of the planet. Downey will be playing Zeke Jackson, a former Union Army man and, I’m guessing, the hero.

I’ve never read the comic – is this one of those comics that only exists to get optioned? – but the basic concept is a good one for a Hollywood summer blockbuster. And it’s coming from summer blockbuster experts – it’s a Dreamworks/Universal co-production, with Ron Howard and Brian Grazer producing along with Roberto Orci, Alex Kurtzman and some dude named Steven Spielberg.

Here’s something interesting: Cowboys & Aliens is being aimed at summer 2010, the same season that Marvel wants for Iron Man II. And this film is re-uniting Downey with his Iron Man scribes of Hawk Ostby and Mark Fergus. It sort of sounds like these dudes are all making themselves pretty unavailable for a rushed production of Iron Man II