The launch has been delayed for two years because of technical glitches. Approved at $1.63 billion, the mission's price tag will be at least $2.2 billion, NASA now estimates. Critics say the cost has really quadrupled since the project was first dreamed up. What no one can doubt is that ambitious missions tend to become costly ones, which jangles the nerves of officials who know how easy it is for a Mars mission to go bust.
Alan Stern, a planetary scientist and former NASA associate administrator for science missions, charged in a New York Times op-ed column last year that the cost overruns of the Mars Science Laboratory are a sign of a "cancer" of spending profligacy that is overtaking the space agency. Stern, now a private consultant, argues that the new rover is too ambitious, with too many new technologies in play, making a cost overrun all but inevitable.
"It's not just that it's a bigger rover. It's also an entirely new kind of landing system. It's also that it's nuclear-powered. It's also that it's carrying multiple instruments far beyond what's ever been done," Stern said in an interview. "We need to go to a strategy where we can access Mars frequently and take advantage of what we've already invented."
NASA officials acknowledge that they are pushing the boundaries of what's possible in Mars exploration. But they say it makes no sense to do the same things over and over again with modest changes.
The new rover, weighing 1,875 pounds, is more than twice as heavy as either Spirit or Opportunity, the remarkably durable rovers that have been sniffing around Mars for the past five years on a mission originally designed to last just 90 days. Those rovers have six instruments each; the new rover has 10, including detectors for organic compounds. The old rovers could reach out, scratch the Martian surface and try to get a sense of things, but the new rover can retrieve a sample and put it in various analytic chambers. Earlier rovers were solar powered, but this one has a nuclear power source that will allow it to operate day and night.
The new rover is more rugged, capable of navigating much trickier terrain. It can operate at higher latitudes with harsher climates. It has its own meteorology station. It has a color camera that shoots video. It can do almost everything but make espresso.
"We need a larger support structure. We need a more capable arm. We need to be able to look at not just the geology but much more the chemistry, much more the organic elements. We have to have a more capable rover," said Jim Green, director of NASA's planetary science division.
He acknowledged that the cost overruns will put a crimp in the planetary science budget, which is running at about $1.3 billion a year. The Mars program specifically will feel the effects, and there will have to be cuts or delays in the next rover mission, scheduled for 2016, he said. But he added that the Mars Science Laboratory will be worth it.
Because it's such a large rover, engineers had to invent a new landing technique, called a sky crane. The rover also needed dozens of motors and gearboxes to accomplish the many tasks outlined by scientific investigators. It was the iffy performance of those motors and gearboxes in tests that forced NASA to pull the plug on the mission's scheduled 2009 launch.
Richard Cook, the project manager, said that in calculating the cost and the amount of time necessary for designing the mission, "we didn't extrapolate how much more complex it was" than the Spirit and Opportunity mission.
Mars is already strewn with the litter of crashed spaceships. Some probes go there and simply vanish. As Charles Elachi, director of the Jet Propulsion Laboratory (JPL), put it, "Mars is very unforgiving."
Elachi tried to illustrate how tricky it is to get a spaceship to Mars and bring it to rest in a specific region on the surface. Imagine you're playing golf, he said.
"Starting in Los Angeles, hit the golf ball toward St. Andrews," he said (for those who aren't golf fans, that's a very famous course in Scotland). "It has to go straight into the cup. And the cup is moving."
And yet NASA has had many successful Mars missions over the past several decades, dating all the way back to Mariner 4, which flew by Mars in 1965. That spacecraft returned 22 images of a dusty, cratered world, instantly ending speculation that Mars might harbor vegetation.
Two Viking landers in 1976 conducted the first experiments looking for life on Mars. The Pathfinder mission of 1997 showed that a cheap, lightweight probe could bounce to a safe landing cushioned by air bags. In the past five years, Spirit and Opportunity have outperformed all expectations, even crawling into craters for a closer look.
But after all that, it remains unknown whether Mars harbors life beneath its surface, or did many billions of years ago, when the planet was warmer and wetter. The new rover might be able to get closer to an answer by searching directly for organic matter that might be associated with living things.
A Mars mission has three basic components, each of which has its special challenges.
First, the probe has to get there. You can't launch a rocket toward Mars just anytime; you must pick a moment when it will intercept the planet at just the right part of its orbit. By missing the 2009 launch window, NASA had to postpone for two expensive years. And hitting Mars is not easy, because its distance from Earth at any given moment is known imprecisely.
The landing is the hardest part. No other country has ever managed to land a functional spacecraft on Mars. No Martian probe has ever been as heavy as the Mars Science Laboratory, and previous technologies for landing simply won't work for something so massive. Thus, JPL has invented an entirely new system for landing -- a sky crane.
The spacecraft will descend through the thin Martian atmosphere using parachutes and rockets to slow its velocity. Because Mars is so far from Earth, a signal between engineers at JPL and the craft will take many minutes to travel, even at the speed of light. That means the spacecraft has to guide itself, sensing its altitude as well as its horizontal and vertical motion.
At 65 feet above the surface -- the descent slowed almost to a hover by retrorockets -- the spacecraft will lower the rover from its belly using cables. When the rover touches down, explosive charges will cut the cables, and the spacecraft will fly off and crash about 200 meters away. And the rover will send a signal to Earth saying it has landed safely.
If history repeats itself, the JPL engineers will have turned purple by that point. Adam Steltzner, one of the inventors of the sky crane system, remembers being unable to breathe during one of the earlier rover landings.
"I was getting the stars and pins and needles as I was starting to lose it," he said.
After the landing comes the exploration. The key attribute of the new rover is that it can operate year-round, in heat and cold, at high latitudes with tremendous fluctuations in daytime and nighttime temperatures.
"Nobody has built something like this before," Elachi said. "And it has to operate on another planet in which every 24 hours you have to go from the Sahara Desert to Antarctica."
He pointed to a quotation prominently inscribed on one of his walls: "Do not go where the path may lead, go instead where there is no path and leave a trail."
Said Elachi: "If you want to have a guarantee that you'll be 100 percent successful, the best thing would be to stay on the pad and never launch."
Photo: Nasa Jet Propulsion Laboratory
