Don't be fooled by the innocuous name—Curiosity, NASA's new Mars rover, is a brute.

Curiosity, which is slated to launch Saturday morning on an Atlas 5 rocket from Cape Canaveral Air Force Station in Florida, is the biggest planetary rover ever built. The six-wheel-drive robot is three meters long—longer than a Smart ForTwo mini car—and its headlike mast rises 2.1 meters above the ground. With a suite of 10 science instruments, Curiosity weighs in at nearly 900 kilograms, more than NASA's last three Mars rovers combined. [Read more about Mars exploration in this special report.]

To put its size in perspective, consider that Curiosity is scheduled to touch down in August 2012, just over 15 years after NASA's first Mars rover began exploring the Red Planet. That rover, Sojourner, stood about 30 centimeters high. Curiosity is designed to roll over obstacles twice that tall.

But brute force is not everything—it's what's inside that counts. "We have our generic bigger and better answer" for what is new about the $2.5-billion Curiosity, says John Grotzinger, a planetary geologist at the California Institute of Technology and the NASA Jet Propulsion Laboratory in Pasadena, Calif. Grotzinger, the mission's project scientist, notes that the rover's technology is simply superior to that of its predecessors—the cameras have better resolution, for instance, and can take high-definition video.

And unlike its predecessors, Curiosity will not depend on sunlight to carry out its mission. Instead its power will come from a radioisotope thermoelectric generator—a 4.8-kilogram supply of radioactive plutonium 238 that decays to produce heat. Devices called thermocouples turn some of that heat into electricity, providing about 110 watts to the rover. (The heat also keeps the rover's systems warm enough to function.) Plutonium 238 has a half-life of more than 80 years, so Curiosity may be able to exceed its 23-month nominal mission lifetime by several years.

But the real key to Curiosity's capabilities are two instruments that can make definitive chemical analyses of what the Red Planet is made of. "This is a mobile chemistry laboratory," Grotzinger says. In fact, the Curiosity moniker came along only in 2009, when a Kansas sixth grader named Clara Ma won a naming contest. Prior to that, the mission was known more straightforwardly as the Mars Science Laboratory. The rover's chemical analyses should dig into what Mars was like billions of years ago, when it was wetter and could have featured niches conducive to life.

The two key geology instruments, an x-ray diffraction unit and a multipurpose sample-analysis system, will be fed by a robotic arm that can scoop up soil or drill into a rock to collect a powdered sample from the interior. The x-ray diffraction instrument will aim a beam of x-rays at samples to reveal their structure and composition, making possible definitive identifications of specific minerals. The sample-analysis instruments, on the other hand, can taste the composition of the surrounding atmosphere or heat solid samples to 1,000 degrees Celsius to release trace compounds within.

With its chemistry tools, Curiosity may help shed some light on all-important methane. Some research indicates that methane, a molecule that has mainly biological origins on Earth, is seeping from Mars in plumes that hint at ongoing geologic—or possibly even biological—activity there. If Curiosity encounters methane in the atmosphere, the rover can make isotopic analyses of the gas to help determine the methane's origin.

"These two instruments are going to provide fundamental, quantitative ground truth that we can tie back to our orbital observations," says Jack Mustard, a planetary geologist at Brown University. Spectrometers onboard spacecraft now orbiting Mars can pinpoint signatures of important minerals, such as clays that form in watery environments, but their true nature can only be determined from up close. That is part of the reason for sending Curiosity to its planned landing site within Gale Crater, an equatorial depression where orbiters have spotted water-linked materials such as clays and sulfates. "If by going there with the Mars Science Laboratory we can ground truth that and then apply that to what we're getting from orbit elsewhere, it's just going to be phenomenal," Mustard says.

Gale Crater should have plenty of attractions to keep Curiosity occupied throughout its 23-month baseline mission on Mars. "We are not a life-detection mission, but our goal is to look for habitable environments," Grotzinger says. "In the case of Gale, we have multiple potentially habitable environments." The clay- and sulfate-rich layers within the 150-kilometer-wide crater form the base of a towering mound about five kilometers high. "It's literally a mountain of layers," Grotzinger says, noting that the mound has the relief of California's Mount Whitney and the layering of the Grand Canyon. "It's this stunning repository of information of the history of Mars," he says. "It's like reading a book."

This deposits could hold clues as to how Mars, in its early history, changed from a clay-producing world to a sulfate-producing one. "Mars has undergone remarkable reorganizations of its planetary systems, and that is reflected in its geology," Mustard says. "The first half billion years of its history are dominated by these clay minerals. Then the planet reorganized itself—it went from neutral pH to acidic. It started to dry out and form sulfates. That is captured, we think, by sedimentary minerals at the landing site."

But before Curiosity can dig into the geologic history of Mars, it first has to get there in one piece. NASA has devised an elaborate scheme to park Curiosity on the surface, just seven minutes after the rover and its descent stage scream into the atmosphere at a speed of about six kilometers per second. The tenuous Martian atmosphere will slow the craft considerably, but the final descent will involve first a parachute, then retrorockets and, finally, a hovering platform, or sky crane, that will lower the rover onto the surface on nylon cords. The intricate choreography of that sequence should produce some white knuckles in the planetary science community come August, but Grotzinger insists that the landing plan is on solid ground, having passed multiple independent reviews. "We've worried about that for years," he says, but "honestly, this seems to be one of the things that people are most confident in."