But then it was suddenly dark. They had driven into the shadow cast by the hillside of the side valley, which sliced deeper and deeper into the canyon. The temperature dropped drastically, and Lance turned up his suit heater. The mesa at the center glowed all the brighter, but their line of visibility along their track shrank to less than ten meters. Sarah switched on the headlights. The substrate looked much different in the artificial light. The thickness of the dust layer also diminished, with some areas being completely free of dust. They rose out of the ground like giant roots or muscles.
“Those are ancient lava flows that the wind keeps clear,” Sarah explained.
The temperature continued to fall. Were they already in the area of the permanent shadow?
Sarah brought the Rover to a stop. “Do you see that?” She was pointing ahead of them. In the light of the right headlight, thousands of tiny diamonds were glittering. “Those have to be ice crystals. They must be crystallizing directly out of the air.”
“Could we collect them?” asked Lance hopefully.
“It wouldn’t be worth it. It can’t be more than a paper-thin layer of ice crystals. They must’ve been gathering here for millennia. I’m just a little surprised at this considering how close we are to the equator.”
Sarah restarted the motor. The Rover’s tires buried the crystals beneath them. What had taken such a long time to form was destroyed in a matter of seconds. We humans really have that down, Lance thought.
It was gradually growing brighter, as the canyon walls receded. They were no longer driving on stone but on a large spit of debris that stretched into the canyon. The river that had gouged out the side valley must have deposited all the stones and sand along there. Lance tried to see if the gravel had been polished and formed by the water, but that didn’t seem to be the case. Maybe the river hadn’t had enough time for that.
His helmet’s external microphone picked up a muffled, scraping sound. It was coming from the rear. Lance quickly looked back. Sarah must have also heard it because she slowed the Rover to a stop. Shit, he thought. The rear section of the Rover was slowly skidding downward.
The thin atmosphere altered the scraping noise. Sarah had also realized what was happening and had hit the gas. They couldn’t let themselves be pushed down the hillside by the Rover’s mass. Lance felt his fear mount as the tires on the front axle spun, but Sarah seemed to remain calm as the Rover tilted sharply toward the valley floor. She shifted down to first gear and let the tires roll slowly. Her response was perfect.
Lance estimated that it was still two kilometers down to the base of the slope. If the Rover eventually went into a slide, there would be no stopping it until it hit the canyon floor. In an emergency, they would have to leap free. However, if they jumped too soon, they would reduce the mass over the front axle, and the tires really would just spin in vain. Frying pan or fire, Lance thought, frying pan or fire.
But Sarah’s strategy was working. The back part of the rover was pointing straight downhill, but the two front axles had now regained their traction. Sarah was driving back uphill on the diagonal. She had to find a way to free the two back axles, or at least one of them, from the loose debris. The Rover’s slant lessened.
Lance considered what he could do to help. Would it help if he pushed from the valley side? But then his body mass would no longer be on the Rover, and that might make the tires spin again. All he could do was let Sarah handle it.
After ten minutes of what felt like slow motion, they reached solid rock. Sarah cut off the engine and slumped over the wheel.
“Thank you, Sarah,” Lance said, hugging her from behind. She turned toward him, and he saw that she was crying. “Hey, you did it.”
“I’m so relieved,” she admitted.
“You need a break. Should I drive for a while?”
“Gladly,” Sarah replied. “But before we set off, let’s load the Rover down with all the rocks we can find. We’ll consume more methanol, but it will help the tires grip better. At least until we get past the strip of debris.”
“Good idea,” Lance said. He climbed down and began to collect some smaller stones.
“If we have room,” he said, “we should take them back with us to the base. Maybe we’ll find some signs of life in them.”
Lance had to stay focused. He admired Sarah’s accomplishment all the more now that he was the one in the driver’s seat. He could sense what he hadn’t noticed as a passenger, the feedback from each individual wheel. Was it gripping the substrate—or starting to slip? If he paid close attention, he could keep the Rover stable as they drove. The two-kilometer altitude difference sloped off at ten-percent grade, and that had to be driven at a walking pace. They reached the floor of the canyon approximately one hour before sundown.
“Should we go a little farther?” Lance asked.
He wanted to make up at least part of the time they had lost. The best route to take would be through the middle of the canyon. Along the right side ran a depression that looked like a former river bed. The ground was quite sandy to the left. The mesa wasn’t composed of volcanic stone, but of unevenly compressed sand. The individual layers were easily distinguishable. The stone was eroding much faster than the volcanic material in the side walls of the ravine. Lance was now glad that they hadn’t planned to investigate the top surface of the mesa. It would have been almost impossible to drive the Rover up the slope. The lowest third or so of the incline reminded him of a steep sand dune—the only difference here was that the slope ran uphill for two kilometers.
“How much longer do you think it’ll take us to reach our destination?” Sarah asked.
“If I believe Mike’s itinerary, we’re about three days out.”
“Okay.”
The ground grew bumpier. The river bed now reached to the middle of the canyon floor. Lance studied the hillside. It looked like a river of lava had come down at this point, causing the river water to recede away from the basalt. He steered the Rover over to the left. The layer of sand on the surface was thicker and the tires sank deeper. It would best for them to keep going so he wouldn’t have to drive back onto this surface later.
As a child, Lance had hated riding his bike through damp sand, but now he had four axles beneath him. It was unlikely that all of the tires would get stuck in the sand at the same time. He looked up. They were now driving along the bottom of a gigantic wall. Unfortunately, it was too dark now for any geological observations of the strata. The material along here had to be harder, though—otherwise it would be more substantially eroded.
Something suddenly crashed behind him. There wasn’t much sound, but it had been very close at hand. Lance looked back, but he couldn’t see anything. Let’s get past this wall, he thought, and then we’ll set up the tent. He was already looking forward to continuing his search for life on the desolate Mars surface along with Sarah.
They reached a niche in the canyon wall. An almost circular, sandy area was located at the center of it. The mesa had receded into the distance.
“All that’s missing are the palm trees,” Sarah declared. “Let’s stop here.”
Lance nodded and brought the Rover to a stop. Sarah was the first one to climb out. She walked around to the back, planning to fetch the tent. Lance followed and saw her suddenly snatch her hand back mid-reach.
“Shit,” she said. “Take a look at this.”
“What is it?”
He joined her and immediately saw what had happened. That must have been the crash from earlier. Their radio was strapped down near the back end of the Rover. It was stored in a sturdy metal container, but it hadn’t stood a chance against the force of the object that had fallen onto it.
“We’ve been lucky again,” Sarah said.
“Lucky?”
“If it had been a half-meter closer to the front, it would have ripped the tent. And another meter and a half ahead, it would’ve hit me.”
Lance felt cold. He had only been thinking about what the loss
of the radio would mean to them. “You’re right,” he said. “We were very fortunate. Tomorrow we need to keep away from these steep walls.”
“I hope Mike and Sharon won’t get worried when they don’t hear from us,” Sarah added.
“That’s wishful thinking. Of course they’ll worry. But once we get back, all will be forgiven. But there’s one other problem.”
“Yes?”
“The four active satellites in orbit were tracking our position via the radio. We’ll have to come up with some other way to navigate now. Unfortunately, Mars doesn’t have a magnetic field, which means that trying to navigate solely by the sun is very imprecise.”
“Don’t worry about that,” Sarah said. “I have another idea. I’ll explain it to you in the morning.”
Sol 58, Hebes Chasma
“So how are we going to find our way now?”
It was still dark. In the headlight beams, Sarah put a finger up to where her lips were. It was a symbolic gesture, though, since she was already wearing her helmet. This was how she had reacted to every one of his questions, at least at those times when she didn’t respond by asking him why he hadn’t paid attention during survival training. Despite his best efforts, Lance couldn’t recall that manual navigation had ever been taught during that course. Had Sarah gone through the same training as he had?
After securing the tent, she walked to the center section of the Rover, which was where a well-stocked toolbox was stored in case they needed to do emergency repairs on the vehicle. Sarah flipped the toolbox’s latch and opened it. After rummaging around in it, she eventually turned around triumphantly and showed Lance a tool. “A sextant,” she said.
He recognized it.
“I could’ve built you one if it had been necessary,” she said. “All I would’ve needed was a little sheet metal, a compass, and two mirrors. But this is easier.”
“Show-off!” he said with a laugh. “Let’s see what you can do with it.”
“We first have to figure out our line of latitude. Mars doesn’t have a polar star, unfortunately.”
“So we’re lost for good?”
“Of course not. We need Deneb, the first-magnitude star in the constellation Cygnus, and Alpha Cephei, also known as Alderamin, the brightest star in the constellation Cepheus. The north celestial pole is located halfway between them.”
Lance looked up into the sky. It was crystal clear. “Good thing we don’t have a dust storm right now,” he said.
“We’d really be up a creek then.”
“I don’t see Cepheus,” Lance said.
“It looks a little like a house with a steep roof.”
He stared up hard into the stars, but couldn’t find anything that looked like a house. Maybe he wasn’t imaginative enough.
“You shouldn’t be looking right up at the zenith. We’re fairly close to the equator, so the north celestial pole should be low over the horizon. But don’t strain anything. I know where it is,” Sarah said. She held the sextant up to her right eye, tweaked the device, and read the value from it. “Good, now for the longitude. That will be easier.”
“I’m really not smart enough to figure that out,” Lance declared.
“That’s nonsense. You can do it. For the longitude, we need either the sun or one of the two moons.”
Lance looked up at the sky again and saw a bright object he recognized. “I found Phobos. No, Deimos.” He remembered that Deimos was the dimmer of the two moons.
“Good.” Sarah handed him the sextant. “Now measure how high it is over the horizon.”
He took the device, held it in front of his helmet, and gazed through the eyepiece. He adjusted its angle so the horizon was visible through it. Now he had to turn the screw on the measuring armature until Deimos appeared in view and came to rest on the horizon line. “What’s this armature called again? I can’t remember the right word,” he said.
“The alidade.”
“Thanks.” And there it was, Deimos, Mars’s moon. Lance was astonished at how bright the chunks of rock in Mars’s sky looked. He turned the screw until the two halves of the image were aligned. He must have actually practiced this earlier since the procedure seemed familiar to him.
He handed the sextant back to Sarah. She read off the angle and double-checked the measurement.
“You don’t trust me, huh?” he asked.
“You were the one who thought he’d never held a sextant before. I’m just making sure.”
“Smart.”
“You did a good job,” she commended him. “I got the same result.” She then moved up to the Rover’s control console.
It took Lance a moment to remember why she needed to do that. She had to check the angle of the moon against a data table. She tapped the screen and then nodded.
He stood next to her. Sarah had obviously saved their coordinates in the map software program.
“We’ve actually made very good time,” remarked Sarah. “We should reach the probe the day after tomorrow. We still have a stretch to do through the Chasma and then up through the notch. After that, it’s straight onward to the probe.”
By early afternoon, they were standing at the spot that Mike had pointed out on the satellite photos as ideal for ascending from the canyon. Lance was sitting at the wheel, looking up. He thought that what they were planning to do sounded insane. There was nothing like this back on Earth. It was as if they had to climb directly from a beach up an 8000-foot escarpment.
Just like on the other side, a side valley sliced down into the Chasma at this point. However, it looked even less like a long-vanished river had gouged it out. Parts of the European Alps looked like this, in those spots where glaciers had receded. But Mars wasn’t supposed to have ever had glaciers like that. There had never been a time in which Mars had been completely covered in snow and ice, at least according to the planetologists’ climate models. And when would there have ever been a glacier here at the equator?
“We really want to go up there?” he asked Sarah.
“We should’ve considered that yesterday before we drove down here.”
“Well, hold on tight.”
The first part of the ascent was still relatively level. Lance tried to forge ahead hard. Lance knew the tires must not be given an opportunity to get buried in the debris. The grade was still less than forty-five degrees, which mean the Rover wasn’t at risk of tipping over. They were able to cover the first 2000 meters surprisingly fast.
After that point, the slope grew much steeper. Lance was amazed that Mike had considered this passage drivable. He must have thought they were experts at the wheel. The greatest danger now was that the Rover would begin leaning toward the valley. If it started in that direction, they would be hard-pressed to keep it upright. Lance couldn’t give the vehicle as much gas anymore, and he was having to avoid the more substantial obstacles in their path. This also meant that they kept getting stuck. When that happened, they had to get out, shovel the tires free, and then wedge something flat underneath them so that Lance could make even a little bit of forward progress.
After the fourth stop like this they decided that Sarah would go ahead on foot, so they could at least save a little time from climbing in and out of the vehicle. Sarah was also able to figure out which spots were especially sandy and could warn him to steer clear of them. They swapped these roles out every 30 minutes. Lance wasn’t sure which was the more stressful job, the tense, unrelenting concentration needed to drive or the sweaty climb as the scout. At least the strain wasn’t all one-sided this way.
They had now reached an altitude that was close to the level of the mesa plateau. According to the satellite images, the substrate here should be harder. They had reached the original granite, which was older than the volcanic rock they had driven over to enter the canyon, and the sediment that had formed the mesa. Too bad Mike’s not with us, Lance thought. With his background in geology, he would have enjoyed seeing all these different formations. Thanks to the extremely sl
ow erosion process, it wouldn’t have been all that difficult for a stonecutter to reach the most interesting spots.
They finally neared the top of the slope. Both stopped.
“Look at that,” Lance said.
“Unbelievable,” Sarah sighed.
Above their heads stretched a 50-meter, perpendicular wall face. It was as if they were supposed to drive the Rover up the facade of a 15-story high-rise. Lance measured the height with the laser rangefinder and then studied the satellite pictures. The wall didn’t show up on them. According to their images, all they supposedly needed to do to reach the top of the canyon was drive a few more meters to the west.
“The satellite’s angle was poor,” he said.
“Yeah, that’s not Mike’s fault,” Sarah agreed.
“Look, we could take a detour,” Lance said. He traced an alternate route with his finger.
“That would cost us half a day at least, and we might end up facing another wall like this one,” Sarah said.
Where did she want to try to get out? “We’d just need to drive back a thousand meters and then head north for two hours. There’s another narrow way to get up there.”
“The sun is going to set in two hours. Would you prefer to make our ascent in darkness, or to spend the night in the wall again?”
Sarah was right, he thought. Neither alternative seemed all that appealing. “So what do you want to do?” he asked, interested to hear what she would suggest.
“Well... we have a windlass, including a pulley and a high-tensile rope. The Rover only weighs a third of its Earth weight. One of us can climb up and secure the winch, and then we can haul the Rover up. We’ve strapped everything down, so what could go wrong?” Sarah asked.
Sure, what could go wrong, Lance thought. They would be trying to haul a bus on the end of a rope up to the top of a high-rise. Standard procedure with no risks at all. He was at least aware of his skepticism.
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