What were those eerily straight lines? Fissures, perhaps, caused by the drying and cracking of the Martian surface? Depressions? Radial streaks of material ejected from craters? It was difficult to explain why Mariner 4 didn’t see the spidery black webs, if indeed they were there. Did the flyby just miss them, with its handful of images only covering 1 percent of the planet? The improvement in image quality for Mariner 4 over telescopic photographs was so striking that the mission scientists had struggled to correlate them with any of the existing pictures of Mars. Perhaps the images were simply taken at too close a range? The mystery of the linear features was one of the reasons NASA decided to launch a second pair of flyby missions to Mars, in 1969. “Photography from the mission is expected to settle this point,” explained the NASA press team. In order to improve the coverage, far-encounter images were added to those taken up close during the flyby. A probe called Mariner 5 had been sent to Venus, so NASA named its next Mars missions Mariner 6 and 7.
By February of 1969, Mariner 6 was tucked inside a glistening nose cone at Cape Canaveral. On Valentine’s Day, the Mariner 6 ground crewmen began a routine test procedure. Unlike Mariner 4’s slimmed-down, simple rocket, the Atlas-Centaur rocket was enormous, towering over the cape like a skyscraper. Ten stories tall, it weighed 150 tons. It was far larger than NASA needed to get to Mars, but it was widely available, having been built in bulk to ferry NASA’s much heavier spacecraft to the moon.
Suddenly, the sound of buckling metal echoed across the launchpad, followed by the piercing wail of an evacuation siren. When the ground crewmen looked up, they couldn’t believe their eyes: The fixed solid launch vehicle, the unshakable, unyielding locomotive of a rocket that was designed to survive a blast into outer space, was collapsing under its own weight, its smooth metal skin rippling and folding like fabric, right in the middle of the launchpad.
Before they could respond, the top of the rocket had tilted to a twenty-degree angle, forming a kink in the cylinder. The balloon tank of the rocket relied on pressure to maintain its rigidity, but the design of the Atlas-Centaur had done away with all the internal structure, to save weight. The crewmen realized that the main valves must have somehow popped open, letting air rush out from fifteen-centimeter openings.
Time seemed to stop as the wires strung to the far side of the launch vehicle pulled taut, then popped. One of the workers rushed to secure the locking bolts as the booster sagged perilously toward the umbilical tower, then thudded onto the platform. Another worker wriggled his way up into the thrust section, trying desperately and finally succeeding in closing the valves, which prevented the crumpled rocket from crashing to the ground.
Those two members of the ground crew received Exceptional Bravery Medals from NASA for saving the Mariner 6 spacecraft, which was carefully extracted from the nose cone and transferred to another Atlas-Centaur. I wonder what it must have been like watching those straight edges warp, looking up at a rocket that only seconds earlier had been firm and solid, trying desperately to orient myself. How can a mountain lean, how can a palisade collapse, how can an Atlas-Centaur ripple? And yet Mariner 6 still launched on schedule, followed a month later by Mariner 7.
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TWO DAYS BEFORE reaching Mars, the telephoto shutters on Mariner 6 opened, and the excitement began. As the spacecraft hurtled in from a hundred and fifty kilometers away, a long-studied linear feature was immediately spotted: the “canal” Coprates. It appeared on the terminator—the line that separates the illuminated day from the dark night—then arced across the disk of the planet and disappeared behind the edge. But by the time Mariner 7 pulled within twenty-four hours of its near encounter, shutters whirring, it seemed evident that Coprates was just a collection of dark dots aligned somewhat east to west, and not even straight.
It was the same for the images that followed, as Mariner 6 raced past the planet, and Mariner 7 followed with a ribbon of images over the South Pole. There was no geometric pattern on the surface. No doublings, no diagonals. Not even the soft angles of a crocheted blanket. It took only eight days for Mariner 6 and 7 to kill the linear features. The schoolboys had been right. For all that time, the lines we’d seen simply weren’t there.
So it was with the whole mission. As the probes collected images with their near- and wide-angle cameras, nothing was what it at first appeared. Mottled areas resolved into crater fields. A “lump” on the southeastern limb of the planet turned out to be a detached haze layer. The W-shaped clouds that had been observed for years were not clouds at all but rather a real surface feature.
Other boundaries once thought to be smooth and regular—along the edge of the south polar cap, between Mare Cimmerium and Aeolis—proved in fact to be ragged and broken. There were uncratered expanses, like in the depths of Hellas, a smooth, featureless terrain that must have been resurfaced somehow. There were fields of chaos—jumbled, blocky, broken terrain with no known counterpart on the Earth or the moon. There was structure to the atmosphere, layers and layers that hadn’t been detected before. There was a dramatic south polar cap, built with carbon dioxide ice. The mission even measured some warm temperatures along the equatorial latitudes, as warm as crisp fall days on Earth. Mars was not the Earth, but it was not the moon either. It was another world altogether. The whole mission, from the crumpling of the rocket to the data the spacecraft returned, seemed to underscore one of the most fundamental things about scientific discovery: that the truth can be a chimeric thing, that the collapse of an abiding belief is always just one flight, one finding, one image, away.
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TOGETHER, THE MARINER 6 and 7 near-encounter images covered 20 percent of the Martian surface. The probes discovered scores of new features, but the images had also undone much of what we thought we knew. We now lacked any semblance of a legitimate map. As the mission team struggled to fit all the new observations together, it became evident that NASA needed another Mars mission, a true mapping mission. And in 1971, Earth and Mars would align when Mars also happened to be at its closest approach to the sun. It would be a particularly favorable time—with Mars close in, there would be less distance for the spacecraft to travel. So in the run-up to the next launch window, NASA readied a pair of twin mappers: Mariner 8 and Mariner 9, identical spacecraft that would go into orbit instead of just flying by the planet. They would establish the Martian geoid, the reference grid from which all points could be identified: latitude, longitude, altitude. Mariner 8 would map the planet’s fixed features—the permanent ones, like deserts and craters—while Mariner 9 would map variable features, the ones that shifted with the seasons. It would do this by entering into a different orbit to image the same places at the same time of day as the Martian year progressed. Between the two missions, NASA hoped to eclipse all the historically crude and static representations of the planet’s surface.
As Mariner 8 and 9 were being fueled, enshrouded, and mated to their rockets, the Soviets readied three Mars missions of their own at the Baikonur Cosmodrome, vying with the Americans to place the first Martian satellite. Despite eight attempted missions, they had yet to achieve any success on Mars.
Mariner 8, the first of the five, blasted off on May 8, 1971, the very moment the launch window opened. Everything appeared to go smoothly for the first few minutes, but then the upper stage of the rocket began to oscillate and tumble. The payload was prematurely cut loose, and Mariner 8 fell through the dark sky. It splashed into the sea and continued falling, all the way down to the bottom of the ocean.
The next day, the Soviet mission Kosmos 419 launched, but the upper stage of its rocket also had trouble, failing to fire the second time, marooning the spacecraft in low Earth orbit for two days before reentering the Earth’s atmosphere. It turned out that an eight-digit code to fire the engine had accidentally been issued in reverse by a human operator; embarrassing, but easy to fix. Over the next couple of we
eks, the Soviet missions Mars 2 and Mars 3 soared into space on Proton rockets.
Mariner 8’s failure had also been caused by something small, an integrated-circuit chip, no bigger than a sunflower seed. A faulty diode had likely failed to protect it from a voltage surge. The Mariner 9 engineers persevered through the rest of May after happening upon a second issue: a short in the propellant system. They hurriedly pulled the spacecraft down from the Centaur, fixed it, then reran a full set of tests. Finally, NASA got the spacecraft back on top of its rocket. On May 30, on a clear blue evening, Mariner 9 lifted into the sky, joining the race to make the first full map of Mars.
SCIENTISTS AT THE Republic Observatory in South Africa were among the first to notice the haze that had begun to spread across Mars. Throughout the summer of 1971, as Mariner 9 journeyed to Mars with the two Soviet probes, those scientists had been peering up from the dome on St. Georges Road, carefully scrutinizing the planet that the three spacecraft were approaching. On September 22, they saw a bright-yellow streak starting to form. It was along the edge of Noachis Terra, a giant southern landmass, part of the heavily cratered highlands. They tracked it as it elongated, first as a thin line, then fattening into a continuous belt of clouds: the beginning of a dust storm.
Within five days, the storm had spread from east of the Hellas basin clear to the south of Syrtis on the other side of the planet. It grew, then retreated, and then suddenly, just weeks before Mariner 9’s arrival, the dust engulfed the whole surface. The features of Mars vanished almost entirely from view, as if the planet were wrapped in a smooth, lacquered cloud. “It looked like a billiard ball,” recalled Norm Haynes, a member of the Mariner 9 engineering team. “We couldn’t see a thing.”
Slowly, a kind of panic came over the team. It was an astounding tactical problem for a spacecraft designed to study the terrestrial features of Mars. The mission was only meant to last three months after it entered orbit. In the early weeks of November, as the spacecraft drew nearer and nearer to its destination, the surface remained completely obscured. Six days before reaching the planet, Mariner 9’s television cameras switched into calibration mode and pointed at Mars. The images that came back were still nearly blank. The mission team reprogrammed the computer system to conserve its data storage. Mariner 9 would circle Mars, waiting, hoping that the skies would clear and the planet would gradually come back into focus.
The Soviets, however, didn’t have the same luxury, as their software was not reprogrammable. Their two orbiters, arriving just two weeks after Mariner 9, both snapped their pictures immediately, returning images of nothing more than impenetrable dust clouds. Like matryoshka dolls, the Soviet orbiters carried small landers but were unable to delay their release, and the landers were promptly sucked into the tempest. One did manage to land on the surface, but the only data returned to Earth were a few lines of a single, incomprehensible image. The transmission ceased less than two minutes after touchdown, before the lander could release the small tethered robot it carried, which was designed to traverse the Martian sands on a pair of skis.
The storm continued to rage. It probably started with a single delicate arc of dust, lifting off the ground like a charmed snake. Because Mars was so close to the sun, it was the peak of summer in its southern hemisphere, with solar heating at its maximum. As sunlight warmed the surface, it also warmed the adjoining layer of air. Warm air rises, and although the Martian atmosphere was thin—less than 1 percent the thickness of ours here on Earth—the rising air nevertheless drew the ultrafine dust along with it as it lifted into the sky. And as more and more dust filled the air, it began to act like a cloud of tiny mirrors, reflecting and scattering the sunlight. As the sunlight bounced, the surface cooled, but the atmosphere warmed, driving breathtakingly fast winds, churning up even more dust from the surface, and creating one of the longest-lasting, most violent dust storms that has ever been observed in our solar system, even to this day.
I wasn’t alive when Mariner 9 reached Mars, but whenever I look at those images of dust shrouding the entire planet, I can almost feel the particles choking my lungs. The summer after my sophomore year of college, I spent ten weeks caked in simulated Martian dust. I was interning in the Planetary Aeolian Lab at NASA’s Ames Research Center. When I walked in to Building N-242 on my very first day, I was struck by the titanic dimensions of the lab. It was one of the largest vacuum chambers in the world—4,000 cubic meters, larger than an Olympic swimming pool—originally built to investigate the buffeting of rockets as they ascended into the atmosphere. The space was enclosed by five walls of solid concrete, comprising a pentagonal tower. I stared up, and as the ceiling ten stories above my head slowly came into focus, I tasted blood in my mouth. When I reached for my gums, the guide I was with laughed, explaining that there was Martian dust simulant all over the ground, coating the walls like brick flour. It wasn’t blood I was tasting, just the sick-sweet tinge of iron hanging in the air.
Everywhere I went that summer, I carried the dust with me. It clung to my skin, my eyelashes, my teeth. There were delicate orange stripes on the undersides of my fingernails, and even though I wore a cleanroom bunny suit, the dust would still puff out of my clothes at night. I’d occasionally spot traces of it in the crevices of the floorboards of the old house where I was staying on Stanford’s campus or in the seats of the van that ferried me and the other interns over to NASA’s Astrobiology Academy each morning.
The dust simulant was called JSC Mars-1A. Two years earlier, nearly ten thousand kilograms of the weathered volcanic ash had been dug out of the side of Pu’u Nene, a cinder cone in the saddle between Mauna Loa and Mauna Kea on the island of Hawaii. It was the closest thing to Mars dust that existed on Earth. We had heaps of it, sieved into various particle sizes, but it was only the finest of fine dust we would use for our experiments. This was because physical forces had thoroughly worked over the surface particles on Mars, ever so slowly fragmenting them, pulverizing the grains until they were as fine as talcum powder. The grains were cracked by cycles of freezing and thawing and rusted over by tiny chemical reactions. But mainly they were whittled by the wind. Most of those gusts were as gentle as a feather duster, but they were incessant, for billions of years.
The Mars Surface Wind Tunnel cut across the dusty floor of the giant chamber, and it was there that I set up my flow-field experiments. My goal was to examine how Martian dust was entrained in the wind and how it would settle over a spacecraft. A new mission was careening toward Mars, and in six months’ time it was going to land in the layered terrain near the Martian South Pole. My project was designed to help gauge how much wind-carried dust might collect on the lander’s broad, flat solar panels—to figure out how much light the dust might obscure, how much power would be suppressed.
The Mars Surface Wind Tunnel reminded me of the forts I’d made as a child—cardboard boxes lashed together with reams of tape. It was just big enough for me to climb inside. In my bunny suit—a papery-thin coverall that left only my face and hands exposed—I would crawl to one end of the tunnel, position the solar panels, then crawl to the other to sprinkle layers of dust where they could be lifted by a giant laminar-flow fan.
When everything was ready, I’d retreat to the control room with the wind-tunnel technician and the other student who was working there that summer. From a tiny reinforced window, I watched as we ran the experiments. When we flipped a switch, the steam plant across the street pulled the vacuum. The chamber would creak as the pressure began to drop. We began at one thousand millibars, normal atmospheric pressure, then lowered it to five hundred, to two hundred, to one hundred.
After reaching six millibars, I would wait a few minutes, then check the controls and begin my measurements. With the press of a button, on the tiniest gust of wind, the dust would balloon into billows. It lofted so easily, like nothing, on the smallest puff from a pressurized air jet. It would cling to the solar panels and I would dutifully recor
d the drop in power readings. But my eyes kept wandering back to that paisley of swirling eddies, cut by shafts of light from the flood lamps above. The dust was exquisite. It filled the meager air with particles that seemed like they would float forever.
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AFTER THE DEVASTATING loss of Mariner 8, Mariner 9 would have to do the work of two orbiters. Though NASA headquarters insisted on prioritizing the mapping of fixed features, the mission team was able to work out a compromise orbit that would allow it to complete at least part of Mariner 9’s original mission: studying the features that were in flux, including something called the “wave of darkening,” a phenomenon that had captivated Mars scientists since the nineteenth century.
The “wave of darkening,” a term coined by Lowell, referred to how the terrain seemed to darken at the poles every Martian spring and progress slowly toward the equator, an event that had been observed repeatedly with ground-based telescopes. What could explain it? Many astronomers had interpreted it as a sheen of vegetation, despite the parched conditions. The darkening was peculiar in that it proceeded in the opposite direction from that on Earth. Here, vegetation grows from the equatorial latitudes, where it is warmest, toward the poles. But on Mars, where water was scarce, it was hypothesized that water would be the limit to growth. Water would become available first near the poles at the end of the local winter, as ice began to vaporize—then liquefy—spreading slowly toward the equator.
The mystery had tempted the imagination of Mars scientists for years. In 1956, a University of Chicago scientist named Gerard Kuiper noted what he thought to be “a touch of moss green” in the equatorial regions. A researcher at Harvard University performed follow-up spectroscopic studies in the late 1950s, detecting specific absorptions among different wavelengths of light over the dark areas of Mars, which were widely interpreted as organics. “This evidence,” he explained in The Astrophysical Journal, “and the well-known seasonal changes of the dark areas make it extremely probable that vegetation is present in some form.” By 1962, his French colleague was even able to establish a rate for the wave of darkening: roughly thirty kilometers a day, according to the photometers at an observatory in the Pyrenees. The bright features on Mars were deserts, to be sure, but it had been impossible to tie the dark areas to underlying geologic structures. Part of Mariner 9’s mission was to determine if those dark areas were evidence of life.
The Sirens of Mars Page 5