CHAPTER 1
Descent
Isoke Ngozi clambered down an old lava flow, the clawed pads of his pressure-suit armor the only thing holding him from crashing down the torturous slope. He had been alone on the mountain for hours.
The faded yellow-gray of the night sky of Venus, unbroken cloud cover tinted orange by the dull glow of the ground, only emphasized that isolation. No one knew exactly where he was. Few knew he was out here at all.
The bulk of the improvised equipment rack he wore warred with his climbing reflexes, but he needed the survival gear, especially the spare pressure tanks. His friends, trapped in their tank-like crawler high on the slopes of this sporadically active volcano, were depending on him to find a support camp at the base of the mountain and start a rescue operation. Whether they could hold out longer than he was in doubt.
Two of his oxygen tanks and one containing hydrogen fuel had been emptied and discarded. The numbers should have been equal. He shared the oxygen with the fuel cell that powered the hydraulics, instrumentation and the cooling system that provided his only active defense against the heat under pressure surrounding him. Only the fuel cell used hydrogen, although in double the quantity of oxygen. His own body was consuming the additional oxygen through the effort of his descent. He was attempting to maintain the greatest pace he could without overexerting himself and wasting that oxygen. Using manual steering with the walker program would cut back on his own consumption, but the robot-control software would not be able to negotiate the broken terrain quickly enough to be of any use.
If he selected fully autonomous navigation, and it ran into a dead end, the computer would begin to trace one edge of traversable territory in an attempt to regain the original course setting. If the way was passable, and Isoke had no assurance of that, the method would work, eventually. Unfortunately, the suit instruments had no ability to detect a navigable route at any great distance or beyond visual obstructions, just as the navigation program lacked the imagination to take shortcuts over unmapped territory.
The only known course, the route of their ascent along a ridge of the mountain, had been cut off by the first eruption, a pair of lateral outbreaks bracketing their position. The meandering alternative the navigator would choose would take far too long. Not only would he be finished but the others as well.
The lava formation spread into a fan over a relatively level area and abruptly gave out. Isoke began a lope on the loose gravel left exposed while trying to keep from slipping. He noticed with alarm that the uncertain footing was causing him to use far more oxygen than he could allow. Reluctantly he slowed to a walk.
The navigator program could handle this stretch. He fed in the course, requested maximum reasonable speed and settled back in his harness. The robot began to run, covering three meters with each low, leaping stride through the dense air. Isoke could see no obstacles ahead, either through his viewport or on his radar display. He checked all his instruments and, though his instincts rebelled, closed his viewport shields against both possible mishaps and the temptation to watch the bounding landscape and wearily succumbed to troubled sleep.
An alarm snapped him into panicky alertness. The window visors flipped open automatically before his vision cleared. He was charging headlong down a crazily tilted wall of bare rock that dropped away sharply to his left. He almost terminated the navigation directive before he realized that the alarm had not been caused by the hair-raising descent. In order to avoid the cliff edge, the robot had been forced to change course.
Isoke silenced the alarm. Almost afraid to watch, he forced himself to endure the plunge. The slope steepened until a second signal sounded. The walker program had finally agreed with his nervous system and was starting to slow the suit down.
Not long afterward, a third warning heralded a sharp change in course. Unable to look for holds, the software was directing the robot along the best path it could handle, in this case, almost back the way he had come.
Isoke canceled the order to the navigator. The machine slowed to a halt. Using the manual controls, he began to climb sideways on the nearly featureless rock in search of a ledge. There was one, a hundred meters below. He angled his way down, picking his footholds with extreme care. The artificial feet seemed suddenly much too large and far away. The rack assembly holding the spare tanks made him feel as if he were strapped into a bookcase. The rough stone left scratches in the protective coating on the arms and legs of his suit but it didn't matter. By the time the corrosives in the atmosphere could eat through that armor, he and his friends would all have been dead for days, at the least. And if he slipped. ... He could spare neither the time nor the effort nor the attention from his meticulous descent to care. He scrambled painstakingly on. He had just reached the ledge and was trying to catch his breath when there was a rumble on the mountainside far above him.
Isoke had never heard an avalanche before, but he was certain of its identity. He felt equally certain of its path. He was like a beetle pinned to a display card. There was no place to hide on the ledge.
What about below? The ledge formed the top of an overhanging cliff. Kneeling awkwardly beneath his supply rack, Isoke spotted a small crack just below the edge and fired a piton bolt into it. The rumble became a roar. He hooked his belt winch to the padeye and tugged at it. The radar unit clamored for attention. He looked up to see the sky above his hatch viewport transform into a rapidly descending ceiling of broken rock.
Desperately he hurled himself headfirst over the edge of the precipice. The anchor hookup immediately flipped him upright. The spare pressure tanks strained momentarily against the equipment netting, but the improvised restraint held. As Isoke's hatch rim clanged against the cliff, he released the safety-cable brake.
A cataract of debris thundered past him as the winch spun out. He dropped like a frightened spider between the two deadly walls, one solid, bleak and unyielding, the other a churning mass of fragments ranging from fine particles carried along by the backwash of the fall to boulders the size of jeeps. He was enveloped in a cloud of swirling dust.
Small rocks began to batter his armor. Isoke realized that the avalanche was spreading by internal turbulence as it fell. He tapped the center of the winch control graphic to halt his descent before he reached a region where larger pieces could strike him.
Before the winch brake could bring him to a full stop, a heavy blow glanced off his shoulder and spun him around. Like a pendulum, he swung dizzily away from the rockfall and as inexorably returned.
He was still trying to drag the winch slide bar to an ascent setting in the wildly spinning suit when a pair of concussions shook him, the first bouncing him high in his harness as the cable sprang back, the next slamming the corner of his forehead against the radar unit.
He regained consciousness with a strange feeling of displacement. The first thing he noticed was the silence. Looking out through his forward viewport, he could see only dull, yellow-gray sky. He turned his head and saw the cliff face hanging beside his left viewport like a giant, rocky curtain about twenty meters away. The movement brought on a sudden lightheadedness.
The hatch. Apprehensively, Isoke strained his head backward for a look at the overhead viewport. It was shuttered. He must have instinctively closed the protective cover during his frantic descent before the rockfall reached him. The corrosion-resistant coating of his suit's head-and-shoulder region was probably badly damaged, but that aspect of his protection would last far longer than the rest of his life-support system.
Isoke looked for the ledge, but it was lost in the heights above him. Moving his head more slowly, he checked the winch reading. Over two hundred meters. Maybe he still had enough cable left on the winch reel to get down. He looked down and wished he hadn't. The cliff simply faded from sight into the thick air below.
Hands clammy from unaccustomed acrophobia, he checked the radar. It was another three hundred fifty meters to the bottom and overhung all the way. Much too far. He was about to reel in when a chilling thought struck him. Suppose his suit was damaged? One unexpected failure could be fatal. He had better check everything first.
The readouts were all within normal limits, and the suit coordination felt good, but the horizontal gyro was starting to run a couple of degrees warmer than usual. Any change could mean trouble, but so far, everything looked all right.
Regretting the fuel the action was costing him, he winched his way back to the ledge.
Five minutes later, he was frustrated and angry. The ledge had turned a corner and given out. He had no choice but to climb back up the mountain and try again. He looked back the way he had come. A chill shot through him. The debris-cluttered trail twisted along the cliff toward an exposed shoulder and terminated abruptly in a fresh, jagged scar where it had been smashed by a giant boulder. There was no way out.
Unless, he thought, he could find another ledge lower down. He returned to his original jumping-off place and hooked up again. This time he descended slowly, checking for ledges, cracks, anything. Three hundred meters later, the cable ran out. He could see one dark line far to his left and slightly above him. The rest of the wall was bare.
He thought of drilling an anchor hole, but he would have to swing to reach the cliff face. He could never hold himself there while he set the bit. What if he tried firing a piton into the surface in front of him? Most rock on the overheated surface of Venus was relatively soft.
He started pumping his legs as if on a child's swing. When he had worked close enough, he kicked hard against the cliff. The next swing would bring him into firm contact.
The recoil of the gun almost stunned him. The bent piton fell away from the nick it had made in the cliff face and disappeared into the depths.
Most rock. Whatever minerals composed the monolith before him must have metamorphosed in this harsh environment, he realized, or they would never support a cliff this high. The slightly cooler air temperatures at this altitude might also have allowed the altered rock to harden to a greater degree than it would have in the lowlands.
He had to try for that black streak. Changing the direction of his swing, he continued pumping until he was rising just beyond the spot he wanted. It appeared to be an igneous intrusion. Hopefully, it was made of softer material than the adamant that surrounded it.
He was having trouble positioning himself on the oscillating cable. Each time he passed the intrusion, he was twisted in a slightly different direction. The drag of the thick air wasn't helping either. Isoke tried to hold his body perfectly still and wait for the right moment. Motion sickness grew stronger with each giant sweep past the mountain face.
He fired. Unable to plant himself as before, he was sent spinning wildly while the pendulum motion continued in interminable swoops. Vertigo closed in around his head and slammed a sudden blow to his nauseated stomach. The severity of the attack doubled him over as far as his harness would allow, sparing his instrument panel the fate of the foot controls. The twisting cable wound up and spun back again and again.
At last the motion damped out. A weakened Isoke cast tear-drenched eyes up toward the starting point of his misery. The bolt was still there.
Once again Isoke pumped his way up to the new anchor point, his stomach too exhausted to protest further. As soon as he was close enough, he grabbed for the piton at the point where it entered the cliff face. It held but shifted slightly with a crunch. It had not penetrated deeply enough. Holding his position with one hand, he set another bolt half a meter farther down. The new anchor gripped firmly.
Feeling considerably better, Isoke fastened his short belt hook to the secure piton and worked the first bolt free. He had others, but they might be needed later. Finding another likely anchoring spot, he replanted the first piton and fastened the short safety line to both. He then activated the fail-safe combination that released the primary cable hook and started to reel it in as it fell past him on the side away from the cliff. Isoke finished reeling in the long cable. The hook mechanism came back up covered with dirt. Isoke looped the cable up through the piton eyes, pulled the loop over and down and tugged the cable hook up. Fastening them together in that way would permit remote release from both pitons. He then released the short safety. Soon he was ready to descend again.
He landed in a niche between the base of the cliff and a long talus pile formed from countless avalanches. Having retrieved his cable, he walked along this corridor, thus shielded from possible additional rockfalls by the towering overhang.
Ahead, a break appeared in the ridge of smashed boulders. Some feature on the slope above the cliff had apparently channeled most of the falling material away from that point. His chance of not being hit by a falling rock would also be improved by his crossing there. Isoke scrambled through, starting several small slides into the outfall side of the pile.
Before him, a relatively gentle slope led downward toward the murky haze of the lowlands. Isoke set the robot controls once more and, overpowered by his own fatigue, collapsed into a stupor.
An alarm woke him. He found himself crossing a level plain with no hazards immediately visible. He checked the display panel. The gyro bearing he had noticed earlier was overheating. He deactivated the navigator and cut power to the horizontal gyro.
The only other way to operate the navigator automatically was with the radar. The mountain would make a handy reference as he moved. He stepped up the power for long-range scanning and was rewarded with a puff of acrid smoke that burned his eyes and made him cough. The unit, apparently weakened by the encounter with the avalanche, had burned out.
Now he was really in trouble. With neither the gyrocompass nor the radar for reference, the robot navigator was useless. He would have to make it out of there himself.
Isoke looked around. The mountain had disappeared into the murk of the lowlands. All he could see was the ground around him fading into the drifting microscopic clutter. He would be lost in a few minutes if he tried to navigate by dead reckoning. He had to keep to a constant heading or he would miss his goal. But how? The planet didn't have enough of a magnetic field to operate a compass.
Harry had told Mike something about that, once. Something about a pine tree. It didn't matter. There were no trees here.
But there were rocks. Rocks worn by the wind. Some had limpetweeds growing on their lee sides, even at this altitude. Isoke remembered the native saying, "The rocks show which way the prevailing wind blows even when the wind is not blowing." Or even blowing in a different direction. He was on the upwind side of the mountain in terms of the prevailing planetary wind. The slow planetary rotation would minimize the Coriolis effect on curvature of wind currents. The wind in the vicinity of the volcano would be drawn toward the broad peak by convection updrafts generated above the huge caldera and increased by the heat of the current eruption. At his present location, one condition would only reinforce the other. He had only to circle partway around the mountain to find a support camp. The nearest boulders all seemed in agreement. He started off, letting the robot do the walking to save oxygen while he did the steering.
The necessity of remaining awake and the monotony of the task of guiding the machine left Isoke time for reflection. As the kilometers fell behind him and the air and fuel tanks were expended with the hours, he became increasingly apprehensive. Chief Scientist Alma Fredericks had moved the advanced laboratory Crawler Six toward the base of the far ridge. Suppose she had also relocated the support camp? He could not walk that far with the supplies he had.
Isoke cut back on his environmental oxygen feed rate in order to keep the fuel cells running for locomotion and refrigeration. To save on the latter usage, he raised the thermostat setting and compensated for the increased temperature by drinking more of the water that was accumulating in his supply tank. He had plenty of water. Too much, really, from the fuel cells and his own metabolism. The by-product of the fuel cells supplied the drinking water. The invisible evaporation from his skin and lungs was scavenged by the scrubber and diverted to the cooling system, which ran the vapor through the heat exchange before flushing it to the outside.
