Fitted out for longer sojourn

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 would paint a skull and crossbones on and enter in a demolition derby.

Compared to the 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, or JPL, in La Canada Flintridge, California, 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 it there on time.

Landing an oversized rover on a far-off planet while facing a drop-dead launch date in the autumn of 2009 is daunting enough to worry even experienced engineers.

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 rovers Spirit and Opportunity, says Adam Steltzner, 44, who heads the 25-member team responsible for the landing phase of the mission.

His team has come up with a landing system he openly compares to a Rube Goldberg contraption. MSL will be lowered like a piano from a hovering spacecraft, called a sky crane.

“Our system looks crazy,'' Steltzner said. “But it's intrinsically safe.''

Important differences

At first glance, MSL has the vaguely insect-like look of the Spirit and Opportunity rovers: a flat, spider-like body with a mast at the front mounted with 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 try to identify the effects of biological processes, such as grains in the rocks that could have been made by bacteria.

“We will have to put a lot of clues together'' to assess the habitaility, Crisp said. “If we get incredibly lucky, we might even be able to see a fossil.''

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 vapourise a spot on the surface from a distance of 30 feet.

The closest thing to a sci fi-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 of finding its chemical signature, according to the scientific team.

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. “I spend quite a few hours every day thinking about it.''

Getting the landing right isn't the only problem facing the JPL team. There is some concern about getting the mission ready in time for the planned launch, scheduled between September 15 and October 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.

“It's burning a million dollars a day, every day,'' said James Green, head of Nasa's planetary division in Washington.

All that money has brought high expectations — and plenty of anxiety from Washington.

Last autumn, 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. Green said Nasa remains committed to the project.

“We had to compromise on some things,'' mission manager Mike Watkins said. “But we still have a fantastic mission.''