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It was the uniform thickness of the layers, the repetitive sequences of rock types, that was so remarkable; on Earth, these were the kinds of layers produced in standing water. You couldn’t rule out some other process—perhaps the layers were made of dust laid down in an ancient, cyclically varying Martian atmosphere and later cemented into rock—but the more Malin looked at the new images of Candor Chasma, the more certain he felt he was seeing sediments that had been deposited in a lake or shallow sea. MOC was letting him look back on an ancient, watery Mars, and the view was spellbinding.
Nearly every place where MOC photographed Martian bedrock—on the walls of craters and channels, on the slopes of buttes and mesas—it revealed more layers. In the ancient cratered highlands, thought to be the oldest terrains on the planet, MOC showed him that the earliest chapters of Martian history were far more complex than anyone had thought. Throughout the ancient crust, interleaved with giant impact craters, were layers of sedimentary rock. They seemed to say that even as the young planet Mars was pummeled by asteroids and comets,
the battered landscape had been dotted by lakes, sand dunes, and drifts of windblown dust.
By this time, Malin had taken on a partner, a 33-year-old geologist named Ken Edgett, who had gone to grad school at Arizona State, where Malin was one of his professors. In temperament, at least, the two geologists were an unlikely pair; one ASU classmate called Edgett a “huggy bear.” But they shared a passion for Mars, and Malin recognized his younger colleague’s skills as a scientist. By the summer of 1998 Edgett was given the important role of choosing most of the camera’s targets. Each day he combed the planet-wide mosaics of old Viking images for the most important places on which to train MOC’s powerful eye. There was a long list of features, from valley networks to polar layers, that had been known since Mariner and Viking, all of which were ripe targets.
But there was so much that wasn’t in the Viking images, or any other previous views, like the strange, twisted rock layers on the floor of the giant Hellas basin, which resembled pulled taffy. And the bizarre texture of the south polar ice cap, which was riddled with circular pits that made it look like a slice of Swiss cheese. And the fact that places that looked smooth in the old Viking images were revealed as astonishingly rough by MOC, while rough terrain seen by Viking often looked smooth at higher resolution.
Mike Carr, who led the team that had acquired the Viking Orbiter images 20 years earlier, came to San Diego to spend a week targeting MOC with Edgett and Malin. Carr had spent as much time studying Mars as any human being, but the planet revealed by MOC was entirely puzzling to him. Sometimes, as he walked the halls of Malin Space Science Systems, his head buzzing with profound and unsettling questions, he could be heard muttering in his mild Yorkshire accent, “We just don’t understand this! It just isn’t the Mars we understood! I don’t get it!”
EVEN AFTER a couple of years in San Diego, Ken Edgett was still vague in finding his way around the neighborhood he lived and worked in. But when it came to navigating MOC’s Mars, he was absolutely masterful. “He knows Mars better than any other person on the planet,” says Malin. “Way better than me.” Edgett spent almost every waking hour in front of the computer screen in his office, stopping only for fast food from a nearby mall. It got to the point where he could glance at any one of the tens of thousands of images MOC had received and be able to say, aided only by the image ID number, where it had been taken. One of the scientists on Malin’s staff who had helped to develop MOC, a geologist named Mike Ravine, had warned Edgett to pace himself, saying that this mission would be a marathon, not a sprint. But Edgett couldn’t help himself. “It was too cool to peel yourself away,” he said.
And during 1999 the pace of work was absolutely relentless. Each day brought a flood of new images, sometimes as many as 300, to look at. Sometimes he was so busy preparing for the next batch of pictures to be taken that he barely had time to study the ones that had just come in. Every new image had to be submitted to NASA’s archive of planetary data and posted on the Internet within six months after it was received. And on top of everything else, he and Malin were given the added task of photographing landing sites for the upcoming Mars Polar Lander mission; after it crashed in December 1999 they used MOC to search—in vain—for the wreckage.


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