Wider than a Hummer, tall enough to roll over big boulders and toting a laser "ray gun" that can zap rocks at 30 feet, NASA's next-generation Mars rover looks like something you'd 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 (MSL) rover being built at the Jet Propulsion Laboratory in La Canada Flintridge, Calif., is an inter-planetary 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 capability to drive over obstacles that deterred earlier rovers, 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 there on time. Landing an oversized rover on a far-off planet, while facing a drop-dead launch date in the fall of 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 airbags that bounce along the surface before opening, as was done with the current rovers, Spirit and Opportunity. Instead, Steltzner and his team have come up with a landing system he openly compares to a Rube Goldberg contraption.

Like lowering a piano from an upper floor apartment, MSL will be dropped on ropes from a hovering spacecraft, called a sky crane.

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-sterilising" 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 ever was, or might still be, habitable for rudimentary life forms.

It also will characterise the potential for human settlement, on the assumption that future presidents will carry through on President Bush's plan to send astronauts to Mars later this century.

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.

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 winter, when the sun is little more than a bright dot on the Martian 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 longer.

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 uncover the 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.

Those compounds include carbon, hydrogen, nitrogen, oxygen, phosphorous and sulfur, the essential building blocks of life. MSL will also identify the effects of biological processes.

Spirit and Opportunity spent a lot of time grinding holes in rocks that turned out to be not that interesting. MSL can short-circuit that time-consuming process with a high-intensity laser, which can vaporise a spot on the surface from a distance of 30 feet. The closest thing to a scifi-style ray gun, the target will give off a gaseous plasma that an instrument called the ChemCam can quickly scan before deciding whether to go in for a closer look.

If there ever was a living creature on Mars, ChemCam, CheMin and SAM will have the best chance yet of finding its chemical signature, according to the scientific team.

"This is the most capable payload we've ever sent anywhere," said mission manager Mike Watkins.
But landing it on another planet is terrifying, said Steltzner, whose team also programmed the landings of Spirit and Opportunity. The proposed sky crane is fraught with opportunities to damage or destroy the rover, Steltzner said.

Getting the landing right isn't the only problem facing the JPL team. There's some concern about getting the mission ready in time for the planned launch, scheduled between Sept. 15 and Oct. 8, 2009. If the launch team misses that, it will be two years before the planets align for another attempt.

Cost is another worry. At $1.8 billion, MSL's mission cost amounts to about 10 per cent of the agency's annual budget.

All that money has brought high expectations - and plenty of anxiety from Washington. Last fall, NASA ordered JPL to remove some of the rover's instrumentation to save money. The heat shield also had to be redesigned, running up costs some more.

However, NASA remains committed to the project. "We had to compromise on some things," said mission manager Mike Watkins. "But we still have a fantastic mission."

Los Angeles Times