CAPE CANAVERAL, Florida - A rover of "monster truck" proportions zoomed toward Mars on an 8.5-month, 354 million-mile journey Saturday, the biggest, best equipped robot ever sent to explore another planet.

An Atlas 5 rocket lifts off from the launch pad in Cape Canaveral, Florida Nov 26, 2011 . The unmanned Atlas 5 rocket blasted off from Cape Canaveral Air Force Station in Florida on Saturday, launching a $2.5 billion nuclear-powered NASA rover toward Mars to look for life habitats there. [Photo/Agencies]

NASA's six-wheeled, one-armed wonder, Curiosity, will reach Mars next summer and use its jackhammer drill, rock-zapping laser machine and other devices to search for evidence that Earth's next-door neighbor might once have been home to the teeniest forms of life.

More than 13,000 invited guests jammed the Kennedy Space Center on Saturday morning to witness NASA's first launch to Mars in four years, and the first flight of a Martian rover in eight years.

Mars fever gripped the crowd.

NASA astrobiologist Pan Conrad, whose carbon compound-seeking instrument is on the rover, wore a bright blue, short-sleeve blouse emblazoned with rockets, planets and the words, "Next stop Mars!" She jumped, cheered and snapped pictures as the Atlas V rocket blasted off. So did Los Alamos National Laboratory's Roger Wiens, a planetary scientist in charge of Curiosity's laser blaster, called ChemCam.

Surrounded by 50 US and French members of his team, Wiens shouted "Go, Go, Go!" as the rocket soared into a cloudy sky. "It was beautiful," he later observed, just as NASA declared the launch a full success.

A few miles away at the space center's visitor complex, Lego teamed up with NASA for a toy spacecraft-building event for children this Thanksgiving holiday weekend. The irresistible lure: 800,000 Lego bricks.

The 1-ton Curiosity — 10 feet tall, 9 feet wide and 7 feet tall at its mast — is a mobile, nuclear-powered laboratory holding 10 science instruments that will sample Martian soil and rocks, and with unprecedented skill, analyze them right on the spot.

It's as big as a car. But NASA's Mars exploration program director calls it "the monster truck of Mars."

"It's an enormous mission. It's equivalent of three missions, frankly, and quite an undertaking," said the ecstatic program director, Doug McCuistion. "Science fiction is now science fact. We're flying to Mars. We'll get it on the ground and see what we find."

The primary goal of the $2.5 billion mission is to see whether cold, dry, barren Mars might have been hospitable for microbial life once upon a time — or might even still be conducive to life now. No actual life detectors are on board; rather, the instruments will hunt for organic compounds.