NASA's next-generation Mars rover is limbering up before its 2011 launch, flexing its new robotic arm and driving up and down ramps.

The car-sized Curiosity rover is set to launch in late 2011 and land on the Red Planet in August 2012. Its main mission will be to assess whether Mars is, or ever was, capable of supporting microbial life.

In one of the latest milestones for the rover, engineers attached Curiosity's single robotic arm and put it through some test moves. [6 Facts About NASA's Curiosity rover.]

The 7.5-foot (2.3-meter) titanium arm plays a central role for Curiosity's mission: It will place samples of soil and powdered rock into analytical instruments on the rover's chassis, NASA officials said. Scientists also plan to mount a camera and spectrometer on the end of the arm, which will allow the rover to examine samples of rock and soil where they lie.

Curiosity is being assembled and tested at NASA's Jet Propulsion Laboratory in Pasadena, Calif., where engineers are performing a series of test drives and maneuvers inside a clean room to check its many systems.

They will soon incorporate the rover's laser-analyzer instrument, which will vaporize bits of rock, then study the chemical composition of the resulting plume. The tool, called ChemCam, arrived at JPL last week, NASA officials said. This graphic shows the instruments that will be onboard Curiosity.

"We're fine-tuning the ability to make the arm go exactly where we want it to go," JPL's Brett Kennedy, a Curiosity robotic-arm engineer, said in a statement. "Next, we'll start pushing on things with the arm."

Curiosity's arm has flexibility through three joints, which are analogous to a shoulder, elbow and wrist, NASA officials said. Curiosity should therefore be able to maneuver its instruments much like a human geologist would. It can bend its arm to get good angles for scraping, grinding and photographing Mars' red dirt.

Curiosity gears up

The arm is the latest addition to Curiosity, which NASA engineers have been building up and testing piece by piece.

In July, scientists mounted a Mars video camera on Curiosity. The new tool will allow viewers on Earth to ride along as the rover descends through the Martian atmosphere and lands on the Red Planet.

Technicians also attached Curiosity's head and neck to its body in July, and mounted navigation and chemical-analyzing cameras to the rover. They then let the six-wheeled craft take its first test-drives, 3-foot (about 1 meter) baby steps.

More recently, Curiosity has been rolling its six wheels over ramps in a JPL clean room, testing its mobility system.

Assessing habitability

Curiosity's mission, expected to cost about $2.3 billion, will build on the recent work done by other NASA craft.

The rovers Spirit and Opportunity landed on Mars in January 2004 and are still exploring the planet today, though Spirit recently stopped communicating with Earth. NASA's Phoenix Mars Lander touched down in the Martian arctic in May 2008, poking and prodding the region around its landing site until its mission ended five months later.

All three probes were charged, in part, with "following the water" — looking for clues to current and previous water activity on Mars, NASA scientists have said.

Phoenix found proof of water ice buried in the Martian soil, far from the poles, in 2008.

Curiosity will look hard for carbon-based molecules — the building blocks of life as we know it — on Mars. The rover will also assess the "habitability" of Martian dirt, helping scientists determine if the Red Planet can, or ever could, support life.