An Atlas V rocket carrying the one-ton rover to the red planet lifted off from the Kennedy Space Center at 10:02 a.m. Eastern Standard Time Saturday morning in a flawless launch.
Some 45 minutes later, a video camera aboard the rocket's upper stage captured farewell footage of the lander and its cruise stage as the package separated and headed for Mars.
A short time later, the payload phoned home to report that all its systems are functioning well.
"Ecstatic is the word," said Doug McCuistion, who heads NASA's Mars exploration program, when asked for his reaction during a post-launch press briefing. "We have started a new era of exploration of Mars with this mission."
Up to now, NASA's program has focused on "following the water" with missions designed to reconstruct from the planet's minerals the history of a liquid essential to life as researchers currently understand it.
But water alone isn't enough, researchers say. Other environmental conditions come into play, conditions that govern the ability of organic building blocks for life to remain stable on the surface or underground, for instance.
The record of environmental conditions early in the planet's history, when it was thought to have been at its wettest, is believed to be written in the layers of rock the Mars Science Laboratory's team has identified in Gale Crater, a 100-mile-wide impact feature with a mountain that soars three miles high from the center of the crater's floor.
After an eight-and-a-half-month cruise, a nail-biting final descent aims to place the six-wheeled robotic chemist squarely in the crater.
If all goes well, Curiosity will initially spend 98 weeks traversing some 12 miles or more – driving, drilling, then analyzing the drill tailings to help build a picture of the environments that existed at the location as the planet made the transition from a wet planet, to a periodically wet planet, to the desiccated orb humans are visiting today.
"This mission is an important next step in addressing the issue of life in the universe," says John Grotzinger, a planetary scientist at the California Institute of Technology in Pasadena, Calif., and the project scientist for the Mars Science Laboratory.
During Curiosity's 354-million-mile cruise phase, scientists and engineers will check out the craft's instruments, making course adjustments. The first adjustment is planned for 15 days from now. On the ground, scientists and engineers will undergo a series of 10 readiness tests to prepare for Curiosity's initial arrival and early operation.
Some 10 years in the making, the $2.5-billion project has had a troubled history. During the spring of 2008 it was clear the project was busting its budget by some 24 percent, which increased to about 30 percent by the following fall.
In addition, the program was failing to meet milestones in ways that increased the risks to its success. In an effort to cope with the rising costs and to ensure the milestones were met, NASA pushed the launch from 2009 to 2011.
Among the lessons: "Whenever you're pushing the envelope scientifically or technically, it's going to be harder than you think it is," says Mr. McCuistion. "We learned lessons about lead times. We really needed those two [extra] years we took."
The tests on how deeply those lessons have taken root aren't far off. NASA remains in discussions with the European Space Agency about cooperating on missions that include a lander in 2018. In 2013, NASA aims to launch MAVEN, an orbiter designed to answer the question: What happened to Mars' atmosphere?
Over the long term, any visions of landing humans on Mars will need to include precursor missions with human arrival and activity in mind, he adds. These range from missions gauging how toxic Mars' soils may be and how it affects hardware to the availability of usable water to developing the ability to deliver heavy loads to the red planet.
The unique landing approach the Mars Science Laboratory is using to reach the surface was driven by its size, heft, and the need to land with a higher degree of accuracy than previous missions required.
"The big issue with getting humans to Mars, frankly, is entry, descent, and landing," McCuistion says. The rover Curiosity represents the largest, heaviest vehicle NASA has ever tried to deposit on Mars. Putting humans on the planet requires an ability to do the same with objects with masses from 10 to 100 times that of Curiosity.
"We don't know how to do that yet," he says.
For now, however, NASA officials and the 250 scientists associated with the Mars Science Laboratory are savoring the moment.
"I'm really excited," says Cal Tech's Dr. Grotzinger. Curiosity will deliver a highly sophisticated package of experiments "exactly where scientists want to go" to hunt for evidence of habitats early in Mars' history that could have supported microbial life.