The eyes of the world will be on Mars, a little red dot in the western sky, as the Pathfinder spacecraft plunges Friday toward a risky touchdown on a harsh, rocky plain north of the Martian equator.
“I’m declaring the success of this mission no matter what happens tomorrow,” NASA administration Daniel Goldin said Thursday, shortly after the half-ton spaceship entered Mars’ gravity field and began to accelerate. “I hope it’s a soft landing, but you can never guarantee that.”
If Pathfinder, swaddled in its air bag cocoon, survives the 55-mph impact, it will be laying the groundwork for a renewed search for signs of life on Mars as well as preparing the way for a possible human expedition in the first quarter of the next century.
Before that distant dream, at least 18 unmanned Martian missions are planned over the next 20 years to study the makeup of the planet most like Earth and most likely to have harbored living organisms.
The final hours before the landing - scheduled for 10:07 a.m. PDT - are white-knuckle time for nearly 200 scientists and engineers at NASA’s Jet Propulsion Laboratory here. The Martian weather report was favorable, but scientists were concerned about the accuracy of their calculations of the landing spot.
“We’re sitting around, twiddling our thumbs, thinking of things that could go wrong,” said Richard Cook, the Pathfinder mission manager.
Goldin said that 20 spacecraft have attempted to reach Mars since the 1960s, and only six have succeeded. Since 1993, the last two attempts, one Russian and one American, each failed.
“This is not an easy thing we’re doing,” said JPL Director Edward Stone. “One of toughest things we can do is to land on the surface of another planet.”
But Donna Shirley, manager of the Mars Exploration Program, said NASA is prepared to carry on, come what may. “If it fails, it’s a setback, but not a disaster,” she said. “We’ll go on with the 1998 launch.”
As Pathfinder closes in on its target at 16,000 mph, even NASA old-timers can’t hide their excitement.
“It’s going to be quite dramatic,” said Robert Manning, flight system chief engineer.
Among the many difficulties and uncertainties to be overcome, the JPL team isn’t sure exactly where Mars is located or where the Pathfinder will come to rest.
The pull of Jupiter and various asteroids has shifted Mars slightly from the orbit determined by the Viking landers 21 years ago. Like a skeet shot, controllers are aiming the space ship at a rendezvous point in space hoping Mars will arrive there at the same time.
There is also concern Pathfinder might come down in a “corrugated” patch of land just west of the target landing zone. That region resembles the Badlands of South Dakota, with hillocks up to half a mile high.
“We’d prefer not to be there,” said Matt Golombek, the project’s chief scientist.
Adding to the suspense will be a four-hour radio blackout between the landing and the time the first crude images of Pathfinder arrive on Earth, about 2:30 p.m. EDT.
The fancy new scientific instruments aboard Pathfinder and its roving sidekick, Sojourner, are not expected to detect any direct evidence of life, past or present, on this trip.
Instead, their task is to check out their landing site, known as Ares Vallis, which astronomers believe was covered billions of years ago by an enormous flood gushing down from the Martian highlands. They hope their detectors will confirm that water, carbon and oxygen, the essential ingredients of life, once existed there.
Future missions, starting in 2001, will collect rocks from three separate regions of the planet, and the first samples will be returned to Earth for detailed study in 2005.
These robotic explorations will also pave the way for the possible human expedition to Mars that Goldin has proposed. The 2001 mission, for example, will include an experiment to see if rocket fuel can be made out of the carbon and nitrogen that form the skimpy Martian atmosphere.
“If we ever want to send people to Mars, we’d like to live off the land,” Shirley said. “It’s like exploring the American West. You don’t send settlers out first - they’d end up like the Donner party. First you send Lewis and Clark. That’s exactly what we’re doing with robots.”
Wesley Huntress, NASA’s associate administration for science, agreed: “We’re the new pioneers.”
Asked why NASA picked the Fourth of July for the Pathfinder landing, Goldin smiled. “We’re Americans. We’re patriots. I think it’s a very, very appropriate way to celebrate Independence Day.”
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