Greetings From Mars
FOR SIX AND A HALF LONG hours mission controllers had been sitting anxiously with their eyes fixed on a single desktop terminal, scanning the computer screen for interplanetary e-mail. Suddenly, just about the time that the towns near the Jet Propulsion Laboratory (JPL) in Pasadena were getting ready to load their Fourth of July fireworks, the screen bloomed with fireworks of its own. As the exuberant sound of the Beatles' ""Twist and Shout'' rang out in the science team's room, the JPL crew got what they'd been waiting for: the first pictures of Mars since the Viking missions of 1976. It was also proof positive that the Pathfinder spacecraft would meet one of its main scientific goals: taking images of the Red Planet. Soon after, the first-ever high-resolution color images of Mars arrived. It was the ultimate Kodak moment. The photo showed gleaming black solar panels atop Pathfinder's open ""petals,'' or sides; the little six-wheeled, microwave-oven-size dune buggy of a rover that was all set to become the first-ever mobile explorer of another planet, and the deflated air bags that had cushioned Pathfinder's pinpoint landing and now lay under the petals like crumpled beach towels. And beyond all that: Mars.
Coming down at 2,250 bits per second, the first images elicited oohs and ahs even from the mission's engineers and geologists. Those landscapes and the hundreds of other images that followed over the holiday weekend showed Pathfinder sitting on a rock-strewn plain under a salmon sky, with hills, crater rims and plateaus in the distance. Pathfinder was in a channel in Ares Vallis - Mars Valley - which geologists believe was formed by a flood of Noachian proportions (a volume of water equal to the five Great Lakes) 1.5 billion to 3 billion years ago. The inundation carried down rocks from the surrounding highlands. One of them, a blue-gray, squarish stone much darker than its neighbors, was ""the one we want to get to,'' said JPL's Matthew Golombek, Pathfinder's project scientist, when he saw the first photos. Unlike its neighbors, it was not covered with Martian dust but was studded with mysterious bumps. Not that anyone was suggesting Romulan Braille, but...
For a whole night and part of the day it looked like Golombek might not get his wish. Commands radioed up from JPL to the lander were not being forwarded to the rover, perhaps because the rover's modified Motorola radio modem had fallen out of sync with the lander's due to frequency drift. Controllers spent the night ""power-cycling'' - turning on and off - the lander's modem, while the rover's cycled automatically once an hour. Late the next afternoon deputy project manager Brian Muirhead barked out the news that brought a sigh of relief that could be felt clear across the JPL campus: ""Flight control, we have rover data.'' The rover was back in the game.
With the sun blazing above Ares Vallis, the rover would slowly unfold its legs like a cat awakening from a long slumber, and reach its full height of an imposing 12 inches. Then it would roll down a steel ramp to become the universe's first ""areologist.'' Like the pontiff kissing the ground after stepping off the plane in a new country, the rover would lower its principal instrument to lock onto the reddish Martian soil at the landing site. For the next 10 hours the Alpha Proton X-Ray Spectrometer would barrage the soil with alpha particles (two protons and two neutrons) from its supply of radioactive curium-244. The alphas excite atoms in the soil, making them emit x-rays or protons. The number, and energy, of the emissions reveal which chemical elements go into Martian soil.
Back at JPL, 119 million miles away, rover driver (and videogame master) Brian Cooper got ready for his big moment by studying a display of the Martian landscape on his Silicon Graphics workstation. By the next day and throughout this week, he would be working the ultimate in radio-controlled cars. Wearing special goggles that turned the image three-dimensional, Cooper would move a cursor of a rover icon to the rock that had the scientists so excited. His computer had calculated how Sojourner, named after the Civil War era abolitionist Sojourner Truth, could get there. Then it would radio up the directions. After 10 minutes the radio signal would arrive on Pathfinder, get relayed to the rover, and Sojourner would be off. Using infrared lasers, like supermarket scanners, to avoid hazards, the rover would crawl along at one inch every two seconds until it reached the rock. Then it would again deploy its spectrometer, which looked like one of those eyes bobbing at the end of a spring on a fright mask, to glom onto the rock and figure out what it is made of. That promised to tell scientists whether Mars did, or does, have the right stuff to evolve life.
Despite the rover glitch, the Independence Day triumph inaugurated a bold new era of planetary exploration by proving that ""better, cheaper, faster'' missions, as NASA Administrator Daniel Goldin puts it, can succeed. ""This is a new way of doing business,'' Vice President Al Gore said in a congratulatory phone call to JPL on the Fourth, ""and its [validity] is being borne out by your dramatic success today.'' Thanks to Pathfinder, the Mars program is on track to launch two spacecraft every 26 months to the Red Planet. One will bring pieces of rock or samples of soil back to Earth by 2005. By the time the last interplanetary ferry returns with its quarry, scientists should know without any doubt whether the planet most similar to Earth ever supported life. Pathfinder may even pave the way to a human mission. In an interview the day before Pathfinder landed, Goldin told NEWSWEEK that the Johnson Space Center in Houston is close to designing a manned mission to Mars that met all his criteria: it would have to carry a price tag below $20 billion, be as safe for the astronauts as engineers can possibly make it, promise a big scientific payoff and be executed in collaboration with other countries. Said Goldin, ""We could have something ready to present to the president by early in the next century.''
The iconoclastic Pathfinder project shattered the conventions of planetary missions. For 30 years, spacecraft have all behaved like cautious tourists who take a breather in the hotel room before plunging into the local scene: after the cruise through space, the craft slipped into orbit around the moon or the target planet. Only after a few loops did the craft, or part of it, land. Not Pathfinder. Pushed to astonishing feats of engineering by the demand from NASA that Pathfinder be designed, built and launched in one quarter the time, and at one quarter the cost, of missions of the 1970s and '80s, JPL built a spacecraft that did what no other has done before. Pathfinder sailed to Mars and plunged directly into the atmosphere of the Red Planet without taking a single orbit to slow down.
Cruising interplanetary space at 12,000 miles per hour relative to the sun, Pathfinder was screaming across the Martian sky from northeast to southwest at a ballistic 16,600 miles per hour by the Fourth of July. (The Viking landers of 1976 cruised down at about half that speed.) Having jettisoned the ""cruise stage'' that had flown it through space, Pathfinder pierced the Martian atmosphere, by then on the dark side of the planet (graphic, page 24). After 70 seconds it was feeling a deceleration force of nearly 20 g's, which made on-board accelerometers kick off an automatic landing sequence whose guts were right in keeping with the Independence Day spirit: a barrage of 41 ""pyro'' devices - firecrackers and mortars.
TWO MINUTES AFTER ENTRY, one mortar shot out a 24-foot parachute that cut Pathfinder's speed by 80 percent. Then the firecrackers started popping like a Grucci finale. In quick succession the pyros blew off the heat shield that had been protecting Pathfinder from the searing heat of entry, shot the ""back shell'' away and made the lander rappel like a mountaineer down a 65-foot-long braided Kevlar tether.
When the radar altimeter sensed the ground about 1,000 feet below, 17-foot-tall, six-lobed air bags, one on each of Pathfinder's four sides, inflated at supersonic speed, giving the whole contraption the look of a gigantic albino raspberry, with Pathfinder completely cocooned inside. Immediately three retrorockets fired with such huge thrust that Pathfinder actually hung motionless in the air for a split second 100 feet above the surface before free-falling, hitting the dusty red plain of Ares Vallis at 23.5 miles an hour.
And hitting, and hitting... Pathfinder landed as no mission ever has: not with the stately touchdown of an Apollo moon lander but like a wild beach ball. Pathfinder bounced crazily across the valley three times, reaching heights of 47 and 23 feet. The undignified landing was forced by the mission's budget: there wasn't a line to pay for a traditional, rocket-assisted landing. When Pathfinder finally stopped, a winch automatically reeled in and deflated the air bags. Then the lander's three sidewalls came partway down like a opening lotus flower. After a journey of 309 million miles, Pathfinder, launched atop a Delta rocket from Cape Canaveral, Fla., last Dec. 4, had landed. The control room at JPL erupted in euphoric applause, hugs, backslaps and even a jig. It wasn't just any landing, either; Pathfinder landed downside down despite all the tumbling around.
Mars is a Whitman's Sampler of virtually every cool feature in the solar system. It has ancient cratered plains like the moon, and the longest (2,500 miles) and deepest (six miles) canyon - Valles Marineris - in the solar system. It boasts the highest volcano of any planet (Olympus Mons), and sinuous channels carved by long-evaporated rivers. Its mostly carbon-dioxide atmosphere exerts less than 1 percent the pressure of Earth's. But otherwise Mars is like a little sibling, half the size but with a day only 37 minutes longer and with terrestrial-like seasons (because Mars's poles, like Earth's, are tilted). In the landing area at this time of year, temperatures range from that of a winter day in North Dakota (minus 10 degrees Fahrenheit) to the coldest ever recorded on Earth (in Vostok, Antarctica) - minus 127.
Embracing the notion that 90 percent of life is just showing up, NASA has always emphasized that Pathfinder's main goal was just to make it to Mars. That alone would prove that the cut-rate approach to space actually works. But such low expectations had space scientists seeing, and even turning, red last week. Peter Smith of the University of Arizona fairly sputtered that ""Pathfinder will do as much good science as supposedly pure-science missions.''
Smith's own experiment, the Imager on Mars Pathfinder (IMP), was snapping away. The stereoscopic, color camera had sprung up from the lander on a jack-in-the-box mast and started shooting soon after sunrise on Ares Vallis. IMP seemed happy - holes that vent gases were arranged in a smile - and so did the scientists. IMP's 24 color filters could make out details invisible to the Viking cameras. The plain where Pathfinder landed was littered with bigger rocks than Viking ever saw, oriented in ways that promise to provide clues to the ancient flood, and made of minerals that may reveal what Mars was like billions of years ago, when scientists suspect it resembled the ancient (and life-creating) Earth. Because the rocks on Ares Vallis were presumably carried down by the flood from the highlands, Sojourner gets to sample rocks from many places without leaving its neighborhood.
KNOWING WHAT THE Martian highlands are made of should solve several puzzles. First, it should nail down whether the ""Mars meteorites'' in Antarctica really are from Martian highlands. If the rocks at the South Pole have the same ingredients as those on Ares Vallis, there will be no question that long before Earth sent spacecraft to Mars, Mars had sent chunks of itself (blasted out by meteor impacts) to Earth. One of those hunks is the meteorite in which scientists last August claimed to detect signs of primitive, extinct life. Second, since the highland crust is thought to be as old as 3.5 billion to 4.5 billion years, studying its rocks could reveal whether the conditions were right, at a time when life was getting start- ed on Earth, for life to spring into being on Mars.
Another payoff from determining what Mars is made of is that ""once you've identified the rock types and minerals,'' says Golombek, ""any geologist can tell you how it formed.'' Did it, for instance, form at a hydrothermal spring? Because such springs get their heat from geothermal sources, they could still survive on Mars even though the rest of the liquid water is gone. Hydrothermal springs, warm and wet, would be ideal places to search for signs of lingering Martian life.
Designing and building Pathfinder and Sojourner cost $171 million, which would have been a mere rounding error in the $3 billion (in today's dollars) Viking budget. Forced to get a spacecraft to Mars on a supersaver ticket, the engineers behaved like kids trying to build a computer using only some castoff circuit boards and ingenuity. Since they couldn't do it the clunky, hidebound way, they came up with the Apple of spacecraft. ""The cost cap forced the technology,'' says JPL's William Dias. Better software, in particular, let NASA get by with tens rather than hundreds of people on the operations team: the computers are so good that one person, albeit working 12- to 14-hour shifts, can do the work of several. ""We did it in one quarter the time and at one quarter the cost of the old way,'' said Goldin. ""If we'd gone with the old style it would've taken another seven years to get off the ground. I told them to get creative, to think out of the box, and they did.''
Although their average age was only thirtysomething and many of them hadn't even made it to high school at the time of America's last successful Mars mission, the Pathfinder team showed respect for the classics. They reproduced the heat shield and parachute design from Viking, for instance. ""We hit on using the old design and then sat around scratching our heads, asking, "What exactly was that [heat shield] formula again?' '' recalls JPL's Rob Manning, the chief flight systems engineer. They actually coaxed some Viking vets out of retirement to help.
But the team also broke new ground. They tested and tested and retested their components as they went along, rather than designing the whole craft completely and then testing it. ""Compared to past missions,'' says Manning, ""Pathfinder was much more, um, empirical.'' In other words, the designers threw every disaster they could think of at the lander and rover. To make sure the lander's petals would open up even if it was smack up against a boulder, for instance, they made the petal motors strong enough to flip the lander - and then they executed a lander backflip at the JPL ""Mars yard'' test site.
The rover designers started off slowly in their tests of Sojourner's grit. At first they merely ran over the toes of a willing scientist. Then they worked up to 10-inch rocks. And the air bags, something no previous space mission has ever used, got impaled. ""Days and days of simulations on a supercomputer still didn't really explain what happened when an air bag hit a spiked rock,'' says Manning, ""so we collected lava rocks, shipped them on a train to a test- ing facility outside Cleveland and then dropped the air bags onto them.'' Having dusted each spike with colored powder, the engineers could tell whether damage to a bag, dropped from the equivalent of 10 stories on Mars, was made by ""Old Yeller'' or some other spike. ""Basically we ripped the hell out of the bags to know how to redesign them,'' says Pathfinder project manager Tony Spear.
Pathfinder, true to its name, has cut a trail for NASA's ambitious 10-year program of Mars missions. ""This gives us confidence that we can build things for only a fraction of the cost of [past] missions and have them work,'' says JPL's Donna Shirley, manager of the Mars program. ""This is the basis for the whole future of planetary exploration.'' And what a future. The Pathfinder lander could last months beyond its ""nominal'' mission length of 30 sols, or Martian days, adding to the photo album as well as making meteorological observations on Ares Vallis as the region changes with the seasons. Next March 15, the Mars Global Surveyor, launched in 1996, is scheduled to begin two years of photographing and precisely mapping Mars's surface. Among MGS's targets: the ""face,'' a rock formation that those who regard ""Men in Black'' as a documentary believe was built by a Martian civilization. Then, every 26 months, when Earth and Mars are aligned so the trip is as short as possible, a lander and an orbiter will take off for the Red Planet. By 2005 some of the landers will start bringing pieces of Mars back to Earth so scientists can scrutinize them for signs of life. And if the engineers come through the way Administrator Goldin expects, it may not be long after until astronauts join in the excavation. The first crewed mission could launch as early as 2011 and take six months to arrive. If that happens, those Martian pioneers may well look back on Pathfinder as the scout that showed the way, allowing earthlings to break the bonds tethering them to their natal planet and set sail throughout the solar system, ushering in a new age of exploration for the new millennium.
Pathfinder's cameras take photos that enable scientists at mission control to study the planet's features. Here is how the images travel to Earth:
1. Snapshots in space: the rover and lander are equipped with electronic cameras that beam images to Earth via the lander's high-gain antenna
2. Encoded light: After entering the camera, light is projected onto a detector, converted into an electronic charge and digitally encoded (below). For color images, this process is repeated three times with red, green and blue filters.
3. Down to Earth: After a 10-minute journey, the coded images reach an antenna in California, Spain or Australia, depending on which is facing Mars.
4. The homestretch: The code is transmitted by satellite or cable to the Jet Propulsion Laboratory in Pasedena, Calif.
5. Decoding the code: Scientists at JPL access the information through computers and run programs to decode it. The code numbers tell the computer how much light fell on each tiny part of the detector. The resulting images, some in 3D, are released to the public on the Internet.
Thirty-seven minutes before touching down on Mars, Pathfinder began a fully automated series of landing maneuvers designed to slow the craft from a speed of about 16,600 mph to around 23.5 mph. Once on the ground, it unpacked instruments designed to analyze what Martian rock and soil are made of and what the weather is like.
1. 37 min. to landing/8,000 mi. from Mars: The entry vehicle separated from its cruise stage (vehicle photo right)
2. 5 min./80 mi.: Guarded by its heat shield, Pathfinder made a fiery entry into the atmosphere.
3. 2 min./6 mi.: The parachute was deployed and, 20 seconds later, the heat shield was jettisoned.
4. 80 sec./ 1-4 mi.: The lander was lowered on a tether, and radar began measuring the distance to the ground
5. 8 sec./ 294 ft.: Tha air bags inflated, insulting the lander for its impact on Mars.
6. 4 sec./ 100-230 ft.: Deceleration rockets ignited, and the lander was dropped from a height of 100 ft.