Where a human geologist would pull out a rock hammer to break off a sample for analysis, Curiosity will use a drill. But since it can't bring its samples to a laboratory on Earth, Curiosity also contains a lab inside its body.

"We take as much of our lab with us in the rover as we possibly can," Simmonds said.

After the rover's arm drills into a rock, it will drop the collected powder into its belly, where two instruments will digest the samples and analyze their composition.

One device combines three tools: a mass spectrometer that uses magnetic fields to separate ionized elements according to their mass; a gas chromatograph to sort chemicals based on how fast they vaporize when heated; and a laser spectrometer to determine which chemicals are present by shooting jets of light at the pulverized rock and examining the fingerprint of the light that shines back. Scientists hope to find carbon, nitrogen, hydrogen and oxygen — elements thought to be essential for life.

The other lab device will use X-rays in two ways: It will shoot rays at the samples to see what electromagnetic fingerprints they produce, and it will bounce rays off the samples to produce recognizable patterns of light and shadows. Those tests will help identify the minerals in the Martian rocks, including those that are likely to house organic compounds.

"For geologists, our currency is minerals," said Matt Golombek, a JPL scientist who works with the still-functioning Opportunity rover. "If we can identify the minerals, we can tell what kind of rock it is and how it formed."

Curiosity can also examine minerals from as far as 23 feet away by shooting a laser and analyzing the light signature of the dust that is kicked up. If the zapped rock turns out to be a dud, the rover can simply move on.

That's important because, for all its advances, Curiosity moves with painstaking slowness. The most basic tasks — like identifying a distant target, maneuvering the robot arm so that its instruments are precisely positioned to examine a rock and then finally taking a sample — can take days, Simmonds said.

In a nod to the long-term goal of sending people to Mars, Curiosity will measure the neutrons, gamma rays, energetic ions and other particles that bombard the planet and might pose a safety hazard for future astronauts who venture to the Red Planet.

In the meantime, scientists will have to put their faith in a machine that's millions of miles away, said Rob Manning, the mission's chief engineer.

"We need to trust that it's doing its job," he said.