Wider than a Hummer, tall enough to roll over boulders and toting a laser "ray gun" that can zap rocks at 30 feet, NASA's next-generation Mars rover looks like something you would paint a skull and crossbones on and enter in a demolition derby.
Compared to Sojourner, the dowdy little robot that tooled around on Mars for three months in 1997, the atomic-powered Mars Science Laboratory rover being built at the Jet Propulsion Laboratory in La Canada Flintridge is an interplanetary beast.
"Nothing like this has ever been sent to Mars before," said Joy Crisp, 49, deputy project scientist for the new mission.
But then, this new rover has a big job: settling once and for all whether the conditions on ancient Mars were suitable for life.
With a full complement of the most sophisticated instruments in NASA's tool chest, and the ability to drive over obstacles that deterred earlier rovers, the Mars Science Laboratory, or MSL, will strip away billions of years of Martian history to reveal its watery childhood and, possibly, evidence of any microbes that swam in those ancient seas.
The challenge is getting it there -- and getting it there on time.
Landing an oversized rover on a far-off planet, while facing a drop-dead launch date in fall 2009, is daunting enough to worry even experienced engineers.
"This is a study in managed paranoia," said Adam Steltzner, 44, who heads the 25-member team responsible for the landing phase of the mission.
Because the rover is so large, it can't be bundled up in air bags that bounce along the surface before opening, as was done with the rovers Spirit and Opportunity. Instead, Steltzner and his team have come up with a landing system he compares to a Rube Goldberg contraption.
The rover, like a piano being lowered from an upper-floor apartment, will be dropped on ropes from a hovering spacecraft called a sky crane.
"Our system looks crazy," Steltzner said. "But it's intrinsically safe."
Fascination with Mars' ability to support life goes back hundreds of years to the time when early astronomers imagined alien boatmen plying its canals.
So excitement was high when the twin Viking missions landed on the planet in 1976.
No signs of life were found. "Self-sterilizing" is the term scientists used to describe a place that appeared more barren than the harshest wastelands on Earth.
The disappointment set back Mars research for a generation. NASA didn't return until the 1990s, when it began trying to unravel the planet's geology and history with new and more sophisticated instruments.
Sojourner came first, clearing the way for Spirit and Opportunity, which landed in 2004.
The two rovers carry several spectrometers and a RAT -- or rock abrasion tool -- which they've used to analyze the mineral makeup of Martian rocks. The rovers' marquee discovery was that a shallow sea once covered portions of the planet's surface.
The next craft to visit Mars will be NASA's Phoenix lander, which is scheduled to touch down near the north pole this summer to analyze the large quantities of ice that have been detected just beneath the planet's surface.
But the most ambitious mission is MSL, which has the broadest possible mandate: to find out whether Mars was, or might still be, habitable for rudimentary life forms.
It also will assess the potential for human settlement, on the assumption that future presidents will carry through on President Bush's plan to send astronauts to Mars this century.
Doing all this requires what Crisp called a "souped-up rover."
On first glance, MSL has the vaguely insect-like look of Spirit and Opportunity: a flat, spider-like body with a mast at the front containing cameras to help the rover plot its course across the planet's surface.
But there are important differences. The 43-inch-high main deck, where the instruments are located, will allow MSL to roll right over rocks that would frustrate Spirit and Opportunity.
Solar panels cover the decks of the smaller rovers. But MSL needs more power for its hungry instrument package than the sun can deliver, particularly in Martian winter, when the sun is little more than a bright dot on the horizon.
MSL is taking its power source with it in the form of a radioisotope thermoelectric generator. The RTG carries 10.6 pounds of plutonium dioxide, which produces heat that is converted into electricity. The mission is scheduled to last one Martian year, which is equal to about two Earth years, although the RTG will be able to supply power for many years.
Like Spirit and Opportunity, MSL carries a drill to bore into interesting rocks. But unlike the smaller rovers, MSL will capture the powder from the drill holes and send them to two onboard instruments for chemical analysis.
The CheMin instrument will bombard the powder with X-rays to determine its mineral composition. An instrument called SAM, for sample analysis at Mars, will cook the powder, looking for organic compounds, which boil off at low temperatures.