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 U.S. 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 (kilometers) 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 (3 meters) long, 9 feet (2.7 meters) wide and 7 feet (2.1 meters) 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.

Curiosity's 7-foot (2.1-meter) arm has a jackhammer on the end to drill into the Martian red rock, and the 7-foot (2.1-meter) mast on the rover is topped with high-definition and laser cameras.

With Mars the ultimate goal for astronauts, NASA will use Curiosity to measure radiation at the red planet. The rover also has a weather station on board that will provide temperature, wind and humidity readings; a computer software app with daily weather updates is planned.

No previous Martian rover has been so sophisticated.

The world has launched more than three dozen missions to the ever-alluring Mars, which is more like Earth than the other solar-system planets. Yet fewer than half those quests have succeeded.

Just two weeks ago, a Russian spacecraft ended up stuck in orbit around Earth, rather than en route to the Martian moon Phobos.

``Mars really is the Bermuda Triangle of the solar system,'' said NASA's Colleen Hartman, assistant associate administrator for science. ``It's the death planet, and the United States of America is the only nation in the world that has ever landed and driven robotic explorers on the surface of Mars, and now we're set to do it again.''

Curiosity's arrival next August will be particularly hair-raising.

In a spacecraft first, the rover will be lowered onto the Martian surface via a jet pack and tether system similar to the sky cranes used to lower heavy equipment into remote areas on Earth.

Curiosity is too heavy to use air bags like its much smaller predecessors, Spirit and Opportunity, did in 2004. Besides, this new way should provide for a more accurate landing.

Astronauts will need to make similarly precise landings on Mars one day.

Curiosity will spend a minimum of two years roaming around Gale Crater, chosen from among more than 50 potential landing sites because it's so rich in minerals. Scientists said if there is any place on Mars that might have been ripe for life, it may well be there.

The rover should go farther and work harder than any previous Mars explorer because of its power source: 10.6 pounds (4.8 kilograms) of radioactive plutonium. The nuclear generator was encased in several protective layers in case of a launch accident.

NASA expects to put at least 12 miles (19 kilometers) on the odometer, once the rover sets down on the Martian surface.

McCuistion anticipates being blown away by the never-before-seen vistas. ``Those first images are going to just be stunning, I believe. It will be like sitting in the bottom of the Grand Canyon,'' he said at a post-launch news conference.

This is the third astronomical mission to be launched from Cape Canaveral by NASA since the retirement of the venerable space shuttle fleet this summer. The Juno probe is en route to Jupiter, and twin spacecraft named Grail will arrive at Earth's moon on New Year's Eve and Day.

Unlike Juno and Grail, Curiosity suffered development programs and came in two years late and nearly $1 billion over budget. Scientists involved in the project noted Saturday that the money is being spent on Earth, not Mars, and the mission is costing every American about the price of a movie.

``I'll leave you to judge for yourself whether or not that's a movie you'd like to see,'' said California Institute of Technology's John Grotzinger, the project scientist. ``I know that's one I would.''