By Sandy CohenLOS ANGELES -- The Sandra Bullock-George Clooney space drama Gravity rocketed to the top of the box office and into industry record books during its opening weekend. The Warner Bros. ( TWX) adventure debuted with $55.55 million in North American ticket sales, according to studio estimates Sunday -- the biggest October opening ever and the biggest openings for Bullock and Clooney. "It's all good news," said Dan Fellman, Warner Bros. president of domestic distribution. He credited director and co-writer Alfonso Cuaron, who takes viewers into orbit with a film that's set almost entirely in space and explores the challenges faced by two astronauts during a spacewalk. Cuaron's team developed equipment and technology to replicate the weightlessness of space. "It's never been seen before, visual effects like this," Fellman said. "Just the space shots are mind-boggling. It looks like you're right there." Last week's top movie, Sony's ( SNE) Cloudy with a Chance of Meatballs 2, rolled into second place with $21.5 million. The animated sequel features the voices of Bill Hader and Anna Faris and a cast of "foodimals," like tacodiles and shrimpanzees. R-rated fare rounds out the top six. Twentieth Century Fox's ( FOX) Runner Runner, starring Ben Affleck and Justin Timberlake, opened in third place with $7.6 million. Warner Bros.' Prisoners, starring Hugh Jackman and Jake Gyllenhaal, crept into the fourth spot. Universal's ( CMCSA) racing tale Rush, starring Chris Hemsworth, drove into fifth place, followed by Don Jon, Joseph Gordon-Levitt's directorial debut about a porn addict looking for love. "The adult drama is back, and fall is the season for the adult drama," said Paul Dergarabedian, senior media analyst for box-office tracker Rentrak. "This is when you get your more challenging films, some of the more esoteric fare, and a lot of those movies, by their nature, have to be rated R."