Aurora

by Kim Stanley Robinson

Then, because Aurora orbited E almost in the plane of Tau Ceti’s ecliptic, and E too orbited very close to that plane; and Greenland lay just north of the Aurora’s equator; and E was so much bigger than Aurora, and the two so relatively close together, there came the time for their monthly midday full eclipse. Their first one was arriving. 170.055, A0.15.

  The sun stood almost directly overhead, the lit crescent of Planet E right next to it. Most of the settlers were outside to watch this. Standing on small dark shadows of themselves, they set the filters in their face masks on high and looked up. Some of them lay on their backs on the ground to see without craning their necks the whole time.

  The side of E about to cut into the disk of Tau Ceti went dark at last, just as the blazing disk of Tau Ceti touched its edge. E was still quite visible next to it, looking about twice as large as Tau Ceti: it blocked a large circle of stars. The very slow movement of the sun made it obvious the eclipse would last for many hours.

  Slowly E’s mottled dark gray circle seemed to cut into the smaller circle of Tau Ceti, which was very bright no matter which filter was used; through most of them it appeared a glowing orange or yellow ball, marred by a dozen or so sunspots. Slowly, slowly, the disk of the sun was covered by the larger dark arc of E. It took over two hours for the eclipse to become complete. In that time the watchers sat or lay there, talking. They reminded each other that back on Earth, Sol and Luna appeared to be the same size in the sky, an unlikely coincidence that meant that in some Terran eclipses, the outer corona of Sol appeared outside the eclipsing circle of Luna, ringing the dark disk with an annular blaze. In other eclipses, either more typical or not, they couldn’t recall, Luna would block Sol entirely, but only for a short while, the two being the same size, and the sun moving eighteen times faster in the Terran sky than Tau Ceti did in theirs.

  Here, on Aurora, during this first eclipse of Tau Ceti ever to be observed, the movement was slower, bigger; possibly therefore more massive in impact, more sublime. They thought this had to be true. As the dark circle of E slowly covered most of Tau Ceti, everything got darker, even the disk of E itself, as what illumination it had was coming from Aurora, which was itself growing darker in E’s growing shadow. The light from Tau Ceti that was bouncing off Aurora and hitting E and bouncing off E and coming back to Aurora, was lessening to nearly nothing. They marveled at the idea of this double bounce that some photons were making.

  Over the next hour, the landscape completed its shift from the intense light of midday to a darkness much darker than their usual night. Stars appeared in the black sky, fewer than when seen from the ship during its voyage, but quite visible, and bigger it seemed than when seen from space. In this spangled starscape the big circle of E appeared darker than ever, like charcoal against obsidian. Then the last sliver of Tau Ceti disappeared with a final diamond wink, and they stood or lay in a completely black world, a land lit by starlight, the starry sky containing a big black circle overhead.

  Off on the horizons to all sides of them, they could see an indigo band, curiously infused with a golden shimmer. This was the part of Aurora’s atmosphere still lit by the sun, visible off in the distance well beyond their horizon.

  The wind still rushed over them. The blurred stars twinkled in the gusts. Over their eastern horizon the Milky Way stood like a tower of dim light, braided with its distinct ribbons of blackness. The wind slowly lessened, and then the air went still. Whether this was an effect of the eclipse or not, no one could say. They talked it over in quiet voices. Some thought it made sense, thermodynamically. Others guessed it was a coincidence.

  About thirteen hours were going to pass in this deep, still black. Some people went back inside to get out of the chill, to eat a meal, to get some work done. Most of them came out again from time to time to have a look around, feel the absence of wind. Finally, when the time for the reappearance of Tau Ceti came, most roused themselves, as it happened to be in the middle of their clock night, and went back outside to watch.

  There to the east, the sky now glowed. Though it was still dark where they were, indigo filled much of the eastern sky. Then the infusion of gold in the indigo strengthened in intensity, and the whole eastern sky turned a dark bronze, then a dark green; then it brightened, until the blackish green was shot with gold, and brightened again until it was a gold infused with greenish black, or rather a mix or mesh of gold and black, shimmering like cloth of gold seen by twilight, perhaps. An uncanny sight, clearly, as many of them cried out at it.

  Then the burren off on the eastern horizon lit up as if set on fire, and their cries grew louder than ever. It looked as if the great plateau were burning. This strange fiery dawn swept in vertically, like a gold curtain of light approaching them from the east. Overhead the charcoal circle of E winked on its westernmost point, a brilliant wink of fire that quickly spilled up and down the outer curve of the black circle. And so Tau Ceti reemerged, again very slowly, taking a bit over two hours. As it emerged the day around them seemed to dawn with a strange dim shade, as if clouded, though there were no clouds. Gradually the sky turned the usual royal blue of Aurora’s day; everything brightened, as if invisible clouds were now dispersing; and finally they were back in the brilliant light of the ordinary midday, with only the sky off to the west containing a remaining dark shape in the air, a shaded area, again as if invisible clouds were casting a shadow over there, a shadow that in fact was that of Planet E, which moved farther west and finally disappeared.

  Then it was just midday again, and it would be for four more days, with E waxing overhead, dark gray again rather than black, the mottling of its own cloudscapes clearly visible, the crescent on its west side slowly fattening.

  Up in the ship, Freya and Badim, watching mostly Euan’s helmet-camera feed on their screen throughout this event, banging around their apartment doing other things but returning time after time to the kitchen to look at it, stared at each other in their kitchen.

  “I want to get down there!” Freya said again.

  “Me too,” Badim said. “Ah, God—how I wish Devi had lived to see that. And not just from here, but from down there with Euan. She would really have enjoyed that.”

  Then the wind came back, hard from the east. But now they knew that there might come a few hours of windlessness during eclipses. And there would surely be other such hours; on this world of constantly shifting light, the winds too would surely have to shift. They might be almost always strong, but as they changed from onshore to offshore, being so near the coast, there would surely be periods that would be still, or at least swirling. They were still learning how that worked, and no doubt would be for a long time to come; the patterns were not yet predictable. That was aerodynamics, Euan remarked: the air moving around a planet was always in flux, supersensitive, well beyond any modeling they were capable of.

  So: wind. It was back, it would seldom go away. It would be a hard thing to deal with. It was the hard part of life on Aurora.

  The good part, the glorious part, they all agreed, was the look of the land under the double light of Tau Ceti and E, especially early in the long mornings, and now, they were finding again, in the slanting light of the long afternoons. Possibly the experience of the eclipse had sprung something in their ability to see. In the ship they saw only the near and the far; this middle distance on Aurora, what some called planetary distance, others simply the landscape, at first had been hard for them to focus on, or even to look for, or to comprehend when they did see it. Now that they were properly ranging it, and grasping the spaciousness of it, it was intoxicating. It was enough to make them happy just to go outside and walk around, and look at the land. The wind was nothing compared to that.

  One day an exploring party came back from the north, excited. Seventeen kilometers to the north of their landing site, there was an anomaly in the generally straight and cliffed coast, a small semicircular valley that opened onto the sea. This was a feature that had been visible from the ship, of course, and people still on the
ship had reminded the surface party about it, and now this group had hiked up to visit it, and having seen it, had come back to base exclaiming its virtues.

  It was either an old impact crater or an extinct volcanic feature, but in any case, a semicircular depression in the burren, with the straight side of the semicircle a beach fronting the sea. The explorers called it Half Moon Valley and said its beach was composed of sand and shingle, backed by a lagoon. In the low land behind the lagoon an estuary cut through the valley, then rose through a break in the low cliff of the burren, first as a braided, gravel-bedded river, then as a set of swift tumbling rapids. And the entire valley, they said, was floored with soil. From space this soil appeared to be loess. The explorers’ closer inspection had indicated it was a combination of loess, sea sand, and river silt. Calling it soil was perhaps inaccurate, as it was entirely inorganic, but at the very least it was a soil matrix. It could quickly be turned into soil.

  This was such promising news that the settlers quickly decided that they should move there. They freely admitted that one powerful attraction was the possibility of getting out of the wind. But there were other advantages as well: access to the ocean, a good supply of fresh water, potential agricultural land. The prospect was so enticing that some of them even wondered why they hadn’t landed there in the first place, but of course they were reminded by people in the ship (who had been reminded by the ship) that the robotic landers had had to give the valley a wide berth, to be sure they came down on flat rock.

  Now they were safely down, and in exploration mode, and their settlement was still quite mobile, being almost entirely composed of landers; they had built their wind wall but not yet started on buildings. So they could make the move fairly easily.

  Over the next few days, therefore, everyone in the station walked up to see the sea valley, and agreed the moment they did that the move should be made. This kind of unanimity was said to have happened so infrequently on the ship (in fact it had never happened) that the people still on the ship were happy to accede to the plan on the ground.

  “As if we could stop them,” Freya remarked to Badim.

  Badim nodded. “Aram says they are acting ominously autonomously. But it’s okay. We’ll all be down there soon. And it looks like a good place.”

  At this point, people from the ship were being ferried down to the moon in modules that then served as their living quarters. Nothing was going as quickly as many on the ship would have liked, but everyone had to agree that nothing more could be done to speed the process. They only had so many ferries, and then some had to be refueled and launched back up to ship. Now that they were going to move the settlement to Half Moon Valley, all the work to expand their living space would be delayed. But a brief delay was felt to be well worth it, given the many advantages that would follow the move.

  So the settlers got to work moving, a task that seemed easy until they began to do it, when the little declivities and breaks in the burren turned out to be more obstructive to moving their living modules than had been foreseen. The shallow little grabens were easy to walk down small ravines into and out of, and so they had hiked to the valley and back without impediment, but moving their modules on wheeled frames, and their construction robot vehicles, and even their rovers, across them was not so easy. And the grabens were all so long, and trending east-west, that they often could not be flanked.

  A best route was found that crossed as few of these troughs as possible, using the algorithm that solves the traveling salesman problem, notorious to all those worried about errors endemic to certain greedy algorithms. But even after extensive cross-checking, the minimum number of graben crossings turned out to be eleven. Each trough had to be bridged, and this was not easy, given the dearth of bridge materials and the weight of the loads on the wheeled carts.

  So it was a slow and ponderous trek, and soon after they began, sunset came again. They did not let this stop them, having decided they could make their trip by the light of E. It hung up there in its usual spot, half illuminated—what on Earth they called a quarter moon, an unusually logical name, it must be said. Just after sunset was as dark as the nights got, as E waxed to full and then waned to the other quarter moon before sunrise. The light cast by quarter E was around 25 lux, which was 25 times the illumination of the full moon on Earth; and though it was four thousand times less than direct sunlight on Earth, and six thousand times less than full taulight on Aurora, it was still about the same illumination as a nicely lit room at night in the ship, which was certainly enough to see by. So they worked in this light, and formed a long caravan of their vehicles, and headed north over the burren. In the end they declared the E light quite beautiful, easy on the eyes, things slightly drained of color but extremely distinct.

  Euan and the rest of the bridge-building team went into action when they came to the edge of the first trough. One of them drove a stone-cutting vehicle to the edge of the trough, well away from where they intended to cross, and put to work a rock saw attachment at the end of the vehicle’s backhoe. Cubes of rock were cut from the side of the graben, then lifted and conveyed hanging from the backhoe to a steep-walled section of graben, where the opposite side was both close and as vertical as could be found. The first cube was hard to get loose, but with some knocking with the side of the backhoe they managed it. Cubes three meters on a side were as large as the vehicle could safely lift. When they got them to the edge of the graben they lowered them into the trough, all very slowly, especially if the wind was gustier than usual. Every four or five cubes, they had to stop and swap out the saw blades they were using, both the circular blades and the thin up-and-down saws that Euan called dental floss. Their printer refurbished worn blades with new synthetic diamond edges, and they attached these and continued cutting cubes and depositing them in the trough to make a rough ramp. When the ramp extended far enough into the trough that the vehicle arm couldn’t reach out far enough to place new cubes, they filled the gaps between cubes with gravel that other teams had crushed, then unrolled by hand an aluminum mesh carpet to provide a bridge surface smooth enough to drive onto. Euan then drove the cutter vehicle out onto this ramp, another cube dangling heavily from its front end, everything looking precarious, especially when swaying in hard gusts of wind, until he reached the leading edge of the new ramp and could lower the next cube of rock into place.

  They were nearly done with this first ramp when Eliza dropped a new cube into place without realizing the trough bottom was not smooth. This was perhaps a result of them working in E light, but in any case, the new cube tilted into another cube already in place in a way that meant their vehicle could neither lift it nor move it, without dangerously tipping the vehicle.

  Euan took over the controls from Eliza to give it a try, but he couldn’t move it either, though he rocked the vehicle dangerously to the side. So it lay there blocking their way, making the ramp impassable, and tilted as it was, it looked like they would have to abandon the entire ramp and start over.

  “Let me try something,” Euan said, and used the rock saw to cut a trapezoidal segment off the top of the tilted cube, then carefully wedged the segment into the gap left under the tilted cube. After attaching the pile-driver tip and doing some hard tamping with the crane, they concluded the combination was going to be stable enough to drive over, and so they continued cutting cubes and placing them in the trough, more carefully than ever, often with Euan given the controls to make the final drops.

  “He’s an artist,” Badim said to Freya as they watched from the ship.

  “That’s why he’s down there and I’m not,” Freya said. “They don’t need Good For Anythings down there.”

  “They do,” Badim said. “They will. It was a lottery, remember.”

  After three days of work, the ramp across the trough was finished. They sent across a robot truck first to test it, and it ground over the aluminum carpet without incident. All was well, and they drove or directed all the other vehicles over the ramp. There were
thirty-seven vehicles in their caravan, ranging in size from four-person rovers to mobile containers that were the modular parts of their buildings. All crossed without incident. But that was only the first of eleven grabens.

  However, they now had their method, and because of that, the subsequent ramps went a little faster. Even the so-called Great Trench, a graben three times wider and twice as deep as the rest, was ramped and crossed in a day. Stopping to swap out the rock-cutting blades became the biggest delay. In this task, both the versatility and the unreliability of humans doing mechanical work was revealed. The operator would set the vehicle arm on the ground with the nut holding the blade to the rotor facing up, and someone would fit the power wrench to the nut and zip it off with a pneumatic blast. Off came the nut and washers, after which they spun the circular saw blade carefully off the short spindle, being careful not to damage its screw threads. Then they carried the blade to the machine truck, where printers would have readied a newly sharpened blade. Go back and spin a refurbished blade down onto the spindle, put the washers on, then the nut; last, apply the power drill and tighten the nut. This was the moment where humans were not as good as a robot would have been, and their tools not adequate to compensate for their inexperience. The problem was they could not tell how tight the nuts were being screwed on by the power drill, and very often, in the attempt to be sure they were tight enough, they drilled them too tight. Threads were stripped, and then there was no grip at all, and the spindle had to be replaced, which took many hours of delicate work; or washers were fused together, or fused into the nut or the blade, such that they could not be separated afterward, even with the power drill at full power.

  This kind of mistake happened so often that eventually they allowed only Euan and Eliza to use the power drills for this task, as they were the only ones who had the touch to do it right. Anyone listening to Euan’s feed to the ship, including Freya and Badim and a few score others, got used to the heavy airy blat of the power drill working, and they also got used to his various favorite curses as he lamented one action or another.