UNCOVERING THE SECRETS OF MARS

By Jeffrey Kluger

From the surface of Mars--where the sky is salmon and Earth is a blue morning star--you probably would have noticed the spaceship coming. It may have been the noise the thing made that caught your attention; although the Martian atmosphere is spent and shredded, it's not too tenuous to carry sound. And it's certainly not too tenuous to make anything that tries to punch through it pay the price, causing the interloper to glow like a meteor as it plunged toward a touchdown somewhere on the ancient world. That you couldn't have missed.

There was, of course, no one in Mars' Ares Vallis floodplain to mark the moment when NASA's 3-ft.-tall Pathfinder spacecraft dropped into the soil of the long-dry valley. But there was a planet more than 100 million miles away filled with people who were paying heed when it landed, appropriately enough, on July 4. For the first time in 21 years, a machine shot from Earth once again stirred up the Martian dust. More important, for the first time ever, it was going to be able to keep stirring it up well after it landed. Curled up inside Pathfinder like a mechanical kangaroo joey was Sojourner, a 1-ft.-tall, 2-ft.-long robot car, known as a rover, designed to trundle away from the lander and investigate rocks all over the desert-like site.

The touchdown was not without problems. Early pictures revealed that one of the airbags that cushioned the craft during its descent had bunched up in a way that hindered the rover from leaving the lander. In addition, the computer aboard Sojourner and the one aboard Pathfinder were having trouble communicating with each other, which prevented the rover from getting the information it needed to rove beyond the immediate vicinity of the lander. But these problems, which engineers promptly set about fixing, did little to dampen the excitement when Pathfinder sent back its stunning panoramas of the eerie orange site where it had landed.

Across the U.S. and much of the world, the ship's successful arrival was greeted with the most attention accorded an otherworldly landing since, perhaps, Apollo 11 touched down on the moon 28 years ago. At the Pasadena convention center, near NASA's Jet Propulsion Laboratory, where the Pathfinder mission was being run, a standing-room-only crowd of more than 2,000 people whooped and wept as the pictures from Pathfinder streamed onto a 25-ft. screen. On the Internet, NASA sites that promised to post the pictures as soon as they became available recorded a staggering 100 million hits on Friday alone. The landing capped off a busy week in which space exploration once again energized the world: Russia launched a cargo ship carrying repair equipment for the beleaguered crew of the space station Mir, and NASA's shuttle Columbia successfully took off for a long-delayed mission.

At J.P.L., the scientists did what scientists do in such signal moments, responding with both exultant overstatement and near-surreal understatement. "This is a spectacular day," said mission manager Richard Cook. Rover scientist Henry Moore agreed, after a fashion. "Nobody," he said, without a trace of obvious irony, "has ever driven a car on Mars before."

Vice President Al Gore called J.P.L. shortly after the landing to congratulate the controllers. President Clinton issued a statement hailing the occasion in more formal tones. "Our return to Mars today," he declared, "marks the beginning of a new era in the nation's space-exploration program."

There was a little hyperbole in the President's remarks, but only a little. In the past several years NASA has been quietly reinventing itself. The slow and swollen agency that grew so fat in the post-Apollo years has been painstakingly downsizing itself to something approaching the agency it was first designed to be when it was founded in the late 1950s: a crew of garage engineers cobbling spacecraft from simple parts and getting the job done both on budget and on deadline.

The results are starting to show. In September the Mars Global Surveyor, already en route to the planet, will settle into orbit and begin a two-year program of photographing and mapping the terrain below. Over the next eight years, up to eight more ships will follow. As these new probes are heading Marsward, others will be dispatched to places as familiar as the moon and as remote as Pluto. "In the next 10 years," says NASA administrator Daniel Goldin, "we'll be flying by, orbiting, landing, roving and bringing back samples from every critical planetary body in the solar system." In the wake of Friday's landing, it's hard not to believe him.

Just getting Pathfinder from Cape Canaveral to Ares Vallis required a remarkable bit of cosmic sharpshooting. Mars is only 4,200 miles across--about half as big as Earth--and the floodplain NASA was aiming for is only 60 miles wide. The barest flutter in the spacecraft's trajectory could have caused Pathfinder to swing far wide of its destination. To prevent the ship from straying too far from its ideal path, the flight plan included five different opportunities for midcourse corrections during which the spacecraft's thrusters could be fired to refine the trajectory. Over the course of the seven months the ship was en route, J.P.L. took advantage of four of those opportunities. When the time came for the fifth one early Friday morning, however, the ship was pointed so true controllers just let it fly on.

"It was a par-five hole from Earth to Mars," said a Pathfinder scientist. "And we shot a four."

Nonetheless, when Pathfinder actually reached the upper limits of Mars' wispy atmosphere, it would still have been possible for NASA to put the ship into the rough. The 1,256-lb. polyhedron-shaped pod was screaming toward the planet at 16,600 m.p.h., a speed that caused it to experience deceleration forces nearly 20 times as great as than Earth's gravity. In order to survive, the spaceship had to approach the planet at an angle of about 14.2[degrees]. "Go in too steep and you could crash and burn," says Pathfinder project scientist Matthew Golombek. "Go in too shallow and you skip back out."

As it turned out, the ship did not exactly thread this navigational needle, slipping into the atmosphere just before 10 a.m. Pacific time at an incline of 13.9[degrees]. In the cluster of cubicles that serve as J.P.L.'s modest mission control, the engineers seated at consoles leaned forward, looking for the telemetry numbers that would indicate that the ship was indeed decelerating as it should. Support engineers stood behind them, squinting at the screens. At his console, chief engineer Rob Manning scanned the numbers flowing back from space. "Spacecraft is now slowing down very rapidly," he said reassuringly.

When Pathfinder was closer than seven miles above the Martian hardscrabble and two minutes from landing, a 40-ft. parachute opened. Less than 1,000 ft. up, a swaddling of shock-absorbing airbags inflated. Immediately after that, a cluster of retrorockets fired for a quick 2-sec. burst, applying a final brake. The almost comically balloonlike ship then struck the surface at about 22 m.p.h., bounced as high as 50 ft. and finally came to rest somewhere in the 4.6 billion-year-old dust.

At first the J.P.L. controllers had no indication that the ship had survived this inelegant landing--and the engineers didn't expect one. The only antenna capable of transmitting through the ship's cocoon of balloons was a single, whiplike stalk protruding from between two of the bags. If Pathfinder landed upside down, however, the antenna would be crushed against the ground. It would then be at least two hours before the bags could deflate and one of three metal petals that make up the sides of the ship could open, turning the entire structure upright. Only then could a more powerful transmitter inside send out a brighter radio beacon.

As it turned out, Pathfinder rolled to a stop in precisely the right position, with its base down and its antenna up. Inside mission control, Manning squinted at his monitor and saw that contact with the ship had been maintained. "A signal is barely visible," he announced with a grin. The controllers burst into cheers.

Preliminary readings from the ship indicated that landing conditions were well within what the engineers had expected. Pathfinder was tilted at an angle of less than 3[degrees], plenty flat enough to allow the rover to disembark. The solar arrays were being bathed by sun and were producing all the power the spacecraft needed. That same sun, however, was providing little heat: the temperature at Ares Vallis was a crisp -64[degrees]F. But Pathfinder, built to function in that kind of killing cold, seemed unaffected. "I'm ecstatic," said flight systems manager Brian Muirhead as the stream of healthy signals poured into J.P.L. "This is way beyond our expectations."

Whether the ship would continue to exceed expectations would not be known until later in the day, however, when the cameras on the lander were at last brought online. Before that could happen, the airbags had to deflate completely, and actuator motors, powerful enough to pull a small boulder, had to draw them under the ship. Then Pathfinder itself had to open up, exposing the Sojourner rover inside and sending back the first black-and-white pictures.

It was just after 4 p.m. when the images began to appear on mission control monitors. They were, by any measure, astounding: scrub plains without the scrub, prairie land without the prairie grass. The eye, schooled to scout such familiar terrain for equally familiar landmarks, scanned briefly for cactus until common sense reminded the viewer that there would be none. "The little engine that could," said Manning after the first clutch of pictures appeared, "did." Added Muirhead: "We've scored a major home run here."

That home run turned into a grand slam a few hours later when the Pathfinder team convened a press conference to unveil the panoramic color images the ship had beamed home. The pictures revealed the Marsscape with a richness and resolution the black-and-white shots couldn't. But it also revealed the problem of the obstructing airbag. It was bad enough luck that one of the mounds of fabric was bunched up in front of a petal; far worse that it was the one petal that was supposed to allow the rover egress. "The great galactic ghoul had to get us somewhere," said Donna Shirley, J.P.L.'s Mars program manager and Sojourner's designer, "and apparently the ghoul has decided to pick on the rover."

Happily, this was a problem NASA had foreseen. In J.P.L.'s so-called sandbox, a roomful of Mars-like rock and soil with a mock-up lander and rover, the engineers had rehearsed a fairly straightforward maneuver that called for Pathfinder to raise one petal, tilting the entire craft 45[degrees], retract the deflated bag further and then lower the petal. The signal to execute the maneuver was sent up shortly before Earth set over the Martian horizon, breaking the communications link until dawn; just before the connection was actually severed, a picture came back confirming that the command had been executed. Though a portion of the bag still blocked part of the petal, there was probably enough room for Sojourner to slip by.

The communication glitch between the lander and the rover took longer to resolve, but by late Saturday engineers believed they had synchronized the two systems and were cautiously declaring that that problem too was licked. Simply because Sojourner was now able to take to the Martian plains, however, did not mean that the going would be anything but painstakingly slow. For all its anthropomorphic sweetness, the plucky rover is a rather dimwitted machine. Its route from rock to rock will be programmed for it by a controller at a J.P.L. console, those instructions will be relayed to it through the Pathfinder lander and only then, if all looks safe, will the car be allowed to push off. Since even signals traveling at the speed of light take 11 minutes to cover the 119 million miles between Earth and Mars, it's impossible for controllers to stop Sojourner from running into an obstacle or over a cliff. The car thus moves excruciatingly slowly--just 2 ft. per minute--reducing the likelihood that it will stumble into trouble. Built-in gyroscopes serve as a sort of on-board vestibular system, helping the rover feel for bumps and potholes; a tracery of five laser beams helps it feel for obstructions. In addition, when Sojourner ventures out it will transmit a regular, pulselike signal back to the lander, which will serve as a sort of vehicular EKG, constantly confirming that all is well.

"People picture this as being like a radio-controlled car, which would be the way to go if we could do that," says Brian Cooper, who will be the one sending the commands that tell the rover where to go. "But with an 11-minute time delay, it doesn't work that way."

Though Sojourner won't get anywhere fast, where it does go should hold a lot of secrets. Ares Vallis was chosen as the landing site in the first place because the now dusty basin was once the largest known floodplain in the solar system. Water rushed into the valley at up to 170 m.p.h., carrying a giant spelunker's bag of rocks with it. Without venturing very far from where the lander set down, the rover could thus use its cameras and X-ray spectrometer to sample geology from all over the planet. Sojourner is scheduled to conduct these studies for up to a month, depending on how quickly the extreme temperatures (from -15[degrees]F by day to -125[degrees]F at night) at last claim it. The Pathfinder lander, with instruments and cameras of its own, could function for as little as a month or as long as a year. Even after it winks out, it will continue to serve an important symbolic function. On Saturday NASA announced that it would rename the spent lander the Carl Sagan Memorial Station.

What was perhaps most remarkable about the spacecraft that set up shop in Ares Vallis late last week is how unremarkable they are. NASA's early interplanetary spacecraft--the Vikings, the Pioneers, the Voyagers--were limousine ships packed with dozens of scientific instruments and countless backup systems. On the surface, of course, this made sense. "If you've never been to Jupiter or Saturn before," says Golombek, "you want a whole bunch of instruments to cover the sphere of what you want to know."

But covering the sphere can get pricey. In 1993, before NASA's Mars Observer spacecraft had even entered orbit around the planet, it blew an aneurysm in a fuel line and spun off into the void, taking nearly $1 billion of NASA funding with it. The twin Viking spacecraft, which accomplished their missions successfully, landing on Mars in 1976, nonetheless set taxpayers back about $3 billion.

When Goldin took over NASA in 1992, he knew that in deficit-conscious times, this kind of trust-fund spending could not continue. From now on, he decreed, the luxury ships of the past would be scrapped. In their place would be stripped-down spacecraft built essentially from available, off-the-shelf parts. What's more, the new ships would not contain a whole science lab's worth of instruments and experiments, but just a handful--generally the ones the scientists deemed absolutely essential to make the trip worthwhile.

The result has been immediately felt. Pathfinder cost $171 million to build, and its Sojourner rover only $25 million. The Global Surveyor orbiter, set to join them at Mars in the fall, carried a price tag of just $152 million. Other ships being developed have had their prices slashed similarly. On the whole, the average cost of a single unmanned spacecraft has plunged from $590 million between 1990 and '94 to $190 million today, and Goldin hopes to get even that pennywise figure down to only $77 million after the turn of the decade. "Because the spacecraft cost less," he says, "we do them faster and we have more in number."

More, indeed. Though Pathfinder and Surveyor will be claiming the attention of Mars scientists for the immediate future, there's a small fleet of similar ships poised to fly. Every 26 months the orbital minuet that Earth and Mars dance around the sun brings them close enough to make interplanetary travel practical. NASA plans to take advantage of those exploratory windows, sending at least three other lander-orbiter pairs to the Red Planet in 1998, 2001 and 2003. In 2005 the agency hopes to exceed even these ambitious plans, launching the first-ever round-trip Mars ship, one capable of landing somewhere on the surface, then flying back to Earth carrying with it a few precious handfuls of rock and soil.

Mars is not the only place the new budget ships will visit. Last spring planetary scientists were buzzing over images returned by the Galileo space probe that provided evidence of a water ocean beneath a thin rind of ice on Jupiter's moon Europa. Where there's water, there's usually heat, and where there's water and heat, there could well be life. Sometime after 2000, NASA is hoping to launch a Europa probe that will orbit the Jovian moon at an altitude of 60 miles--about the same distance at which Apollo spacecraft used to orbit Earth's moon--photographing its surface and taking radar soundings to look for water beneath its crust. If the radar picks up the telltale echoes of liquid, another spacecraft would be sent to land on Europa. Once there it would release a small cylindrical probe with a heated tip that would melt through the ice layer and propel itself through the frigid ocean, looking for signs of life.

Still another spacecraft might be launched to fly by Europa and drop a 20-lb. sphere onto its surface. Striking the frozen crust with the force of a suitcase full of TNT, the cosmic cannonball would release a mushroom cloud of ice particles into space; the mother ship would then fly through the crystalline mist, collect a bit of it and carry it back to Earth for analysis.

Other hoped-for missions include a 13-year, 4 billion-mile-plus journey to Pluto and its companion moon Charon, tentatively set to launch in 2001; a comet-rendezvous mission that will take off in February 1999, fly by Comet Wild 2 in 2004 and fly back home with a bit of material from its diaphanous tail; and perhaps even a much-dreamed-of journey to Neptune's planet-size moon Triton. Says Goldin: "We're going to have the most aggressive exploration of our own solar system in the history of the human species."

Not everyone at NASA is convinced that Goldin's thrift-shop ships are up to the trips. "Faster and cheaper is not necessarily better," says Ray Newburn, a veteran astronomer with 41 years of experience working on J.P.L. missions. "It's nice to have some small missions where you don't have all your eggs in one basket. But you can't always be cheap about missions that go way out and have to last a decade or more."

Rich Terrile, a J.P.L. planetary scientist, doesn't agree. "The new missions are cheap," he says. "So if one fails, it's not the end of the program. We're not going to build the dinosaurs anymore."

Whatever shape NASA's future missions take, for now the attention of the agency and the world is on Pathfinder. The data it will be sending back this week may help us understand better that most profound of all mysteries: Did life ever exist anywhere else in the cosmos? Already Pathfinder has revived morale in the global space community. More important, it continued the only known cultural-exchange program anywhere in the cosmos. Mars and Earth, after all, have been throwing rocks and machines at each other for eons. Last summer an ancient Martian meteorite gave the creatures of Earth the first compelling evidence of life beyond our own. This summer the creatures on Earth answered back, sending our sister planet evidence not just that terrestrial life exists, but that it is--when it tries to be--wonderfully intelligent.

--Reported by Dan Cray/Pasadena and Joanna Downer and Dick Thompson/Washington

With reporting by DAN CRAY/PASADENA AND JOANNA DOWNER AND DICK THOMPSON/WASHINGTON