While out looking at the progress on the dish, a message popped up on his HUD, tasking him to go to the western end of Kasei Valles. A seismic and weather station had abruptly ceased reporting in mid transmission. Such failures were rare. Probably it was an antenna failure, that being the only non-redundant part, although on one occasion a shelter power system had exploded with catastrophic results. He queried the AI in Rollagon 04 for its status and asked for a route. In seconds it appeared on his helmet display. The track would pass close enough to two other unattended stations to make it worthwhile diverting from his course. Records told him that none of them had been visited by humans since their installation by AIs during the first year. He set out that night and arrived at the first of them, poised on the lip of Sharonov, at noon of the next day.
As he neared the site, the AI established communication with the station AI and quickly determined that all was OK, in effect making any human involvement unnecessary. However, Sam liked to look for himself. While he suited up, the station AI used a brush attachment to clear the sand and fines that had partially blocked the airlock door.
He walked around the shelter. It was small, just under five meters long, two and a half meters wide, and a scant two meters in height. He looked intently for blisters and other irregularities in the exterior. The heat exchangers were covered with a fine layer of dust. The nearby manipulator arm held a brush-like attachment. Good, he thought, it had been cleaned recently. He examined the antenna and visually checked its orientation. Reaching up he shook the pole, grunting with the effort. Stiff. Good. Cable was OK, too.
Satisfied that things were as they should be, he opened the shelter door, eased himself into the narrow confines of the air lock, and cycled through. Jets of compressed air blasted him from helmet to footpads. He ran his finger down the front zipper and around those on the cuffs on his gloves, boots and helmet. After the AI gave the OK, he popped the helmet faceplate and cautiously sniffed the air. It was cold and musty with the faint smell of fresh blood, but otherwise seemed OK. He stripped off his gloves and outer boots and entered the small equipment room.
The noise of the air circulation system seemed very loud after the quiet of the Rollagon. A cooling fan was probably running rough. Lights came on, low at first, gradually increasing in intensity. The room was tiny and spartan in its furnishings. Along the left side there were two full size racks of mission equipment, a power and life support rack and a half height rack topped with an AI carapace. A narrow space less than a meter wide and three meters long allowed access to the equipment. The manipulator arm that allowed the AI to service the equipment was folded against the side. Against the end wall, a small stool faced a computer terminal.
Sam found he could not fully stand up and had to hold his head tilted to the side. The shelter had not been designed for any more than temporary occupancy by humans. He sat down on the stool and turned on the screen.
"Greetings, how may I be of service?" A blinking cursor greeted him.
He flipped through the stats screen. It showed the shelter equipment was serviceable, that it lacked for nothing, and that it met all reporting parameters. That was it. He learned nothing that he couldn't have determined from the comfort of the Rollagon's command chair from anywhere on the planet, but then that was Sam. He switched to verbal mode—default voice.
"There is a cooling fan running rough."
"I am aware. The fan is not essential. A spare is on-site. It will be replaced during the next maintenance cycle in two weeks time."
"Understood."
He was about to turn off the terminal when his eye fixed on one stat that was not normal. The site had been sending and receiving large amounts of data over the main link on a continuous basis for quite some time—for six months in fact. The last comm was to his AI, but nothing since he had entered the shelter. It seemed unusual for an uninhabited site with such limited function to have such a high data throughput.
Exploring deeper into the stats, Sam found that the data was not actually mission data—the addresses were global and numerous, rather than specific to a single data collection center. Did AIs gossip, he wondered? He was hardly an expert on these particular systems, but something did seem odd.
"Well, thanks, and keep up the good work." There was no response. After a few seconds he closed down the terminal.
He exited as he always did, walking backward from the far end, taking one last look at everything, ensuring that it was as it should be. As he closed the door, the lights dimmed. He suited and returned to the Rollagon. He said nothing to the Rollagon AI about the exchange. Perhaps they did chat amongst themselves.
He resumed his journey to the second station, arriving just before dark. This was identical in every respect to the first and just as exposed to the wind.
He performed his external inspection. In a small dune on the lee side of the shelter were the unmistakable tracks of a wheeled AI. He found nothing amiss and entered the shelter, where the AI greeted him in the same manner as the previous.
Satisfied that all was as it should be, Sam prepared to leave. As a last act, he checked the message traffic from the shelter. Here too, large volumes of data had been sent and received from all over the planet.
It being late, he decided to spend the night parked at the shelter. He puzzled over the data anomaly as he ate a simple meal of pasta washed down by decaf coffee. There was no reason that he could see for it, but that did not mean that there was something going on. It was none of his business and it was out of his field of expertise.
That done, the work day was over. It was too early to sleep and he felt no desire to go for a walk, so he watched a favorite sci-fi vid, "Destination Moon" for the umpteenth time. Before the end he became sleepy and shut it off. He crawled in to his bed and, after dimming the lights, looked out the window. From this angle the outline of the shelter could be faintly discerned against the backdrop of the Milky Way. He fell quickly asleep and dreamed of stars.
He awoke suddenly much later, finding himself instantly fully awake and in a cold sweat. Lying there in the dark, he had the feeling of being watched. He adjusted the window until it was opaque. Soon though, feeling somewhat foolish, he set it back to clear. Unable to fall back to sleep, he pulled down the terminal from above the bed and turned it on.
He searched the Matrix technical pages until he found the Seismic and Weather Stations newsgroup. In maintenance mode, he brought up the first of the two stations he had been at today. Searching through the pages, he saw nothing unusual in any files. The data rates were what would be expected—low. Video images of inside and out revealed nothing. He switched on the outside lights and panned the exterior camera around the front, and then to the immediate foreground. He could clearly see his own footprints from earlier in the day. Beyond the circle of light the camera revealed nothing.
He snapped off the light and camera and resumed his search of the data pages. Looking back he found the spike he was looking for—on August 35 of first year. He brought up the last station and was mildly surprised to find that it was booming out data at a high rate. Digging still deeper, he found that it was engaged in communications with three other stations and a data node at the MHM. Suddenly the rate dropped to nil, then settled at a low rate, one way, to the node.
He looked up and out the window. The uneasy feeling returned. He snapped off the terminal and pushed it back up out of the way. He half rose from the bed in response to an impulse to go outside, then thought better of it. He looked out the window again. There was nothing there and never had been. The shelter was now invisible. Giving in to a tired but puzzled mind he pulled the covers over his head and went to sleep.
Warned only a few seconds before the lights came on, B118 spun its wheels to pull back out of the range of the light. It withdrew until it knew it could not be seen and waited. After a brief period of silent waiting it turned and headed back out into the dark.
In the morning, after a light breakfast, Sam pulled up to the
front of the shelter and stopped. The AI reported that all was normal. He wheeled the Rollagon in a tight circle around the pad. Everything looked OK. In the daylight he could see multiple AI tracks. Judging from the number and direction, this site had been visited a number of times. He knew that AIs required replenishment, but he could not imagine why one would be here in this remote location. It was, he supposed, something else for an inquiring mind to figure out, but not today.
He continued on to the third site, intending to arrive before sunset. It was located on the edge of the Lunae Planum plain above Kasei Valles and had been placed there along with its peers to gather data on the katabatic winds and seismic characteristics of the Kasei Valles area.
Sam was watching a Tri-D video of the news from Earth and the AI was doing the driving when the Rollagon suddenly ground to a halt. He thought that it wanted him to take over the controls, but before he reached the command chair, the Rollagon spoke:
"Something is wrong here. It should be possible to see the shelter and tower from here, but it is not."
"What?"
"I mean that the shelter and the tower are gone."
Sam peered through the window in the failing light. The ground in front sloped gradually up and the view revealed nothing to his eyes. The AI was adamant that they were in the correct location and Sam could not argue that point. He called up the photos of the area. There was nothing on file less than two months old that was capable of resolving an object the size of the shelter. It was clearly shown on the older images. He considered putting in a request for one of the satellites to be repositioned, but knew that this would take too long, and besides, there were easier ways to resolve the mystery.
"Well, proceed."
"Yes, but I suggest that we deploy the GPR and advance very slowly."
"OK, do it."
He felt the Rollagon tremble as the GPR mast rotated from its stowed position, dropping down in front of the command window. The darkened screen glowed softly—in red. In a moment the sub-surface immediately underneath the Rollagon was revealed.
"Ice, up to 45%," the AI announced, "Close to the surface—within five meters. The overburden is rubble, ice, sand, and dust with no integrity. It extends down to twenty-five meters, then gives way to bedrock."
The Rollagon crept ahead at a snail's pace for several minutes. Sam watched the GPR intently. The ice was there all right, but it was discontinuous. Just enough to be trouble this close to the edge of the valley. The Rollagon stopped again.
"I suggest that this is the limit of safe approach for this vehicle. The shelter should be clearly visible now, if it is there."
"Well, it's clearly not," Sam replied. "I'm going out for a look."
Surprisingly, he got no argument from the AI. He suited up hurriedly and climbed down onto the surface. In his ear, he heard the AI. "If you are going to do this, I suggest you rope in."
"OK, just to please you," Sam countered. "Where do I find such a thing?" The cover of a small access panel on the underbelly of the Rollagon CHM popped open. Sam looked in and pulled out a long plastek rope stored within—a rope which, upon examination, was unreassuringly thin. More like string! He clipped one end onto his belt, the other to a ring in the panel recess. Playing the line out behind him as he went, he started toward the valley.
The AI spoke in his ear.
"The shelter was fifty meters in front of you and was formerly 100 meters from the valley edge."
"Well, it ain't no more."
"That much is obvious."
"I am going up to the edge."
A human crewmate might have been expected to offer the entreaty to be careful, but the AI remained silent. Uncharacteristically silent, Sam thought, looking expectantly back towards the Rollagon. He crept slowly up to the edge and, holding the thin line taut in his hand, peered cautiously over the fall. It was a sharp cookie cutter type of fracture. There was what he judged to be a drop of about twenty-five meters to a slope of thirty degrees that ran down onto the valley floor, far below. In the dim light he could see no sign of the shelter, but it would be down there, somewhere. Maybe clear across the valley.
"I don't see anything, but that doesn't mean it isn't there. I'll have another try tomorrow."
With a final look he started back to the Rollagon, coiling the line in his hands. They pulled back until the GPR showed solid ground underneath and parked.
During the night Sam felt the Rollagon tremble and rock like never before in the fantastic winds that roared across the open land and down into the big valley at 300 kilometers per hour. The audible whisper of sand along the exterior and the periodic tick of pebbles on the hull was unusual, and indicated the extreme strength of the winds. In the early morning hours the winds diminished and Sam judged it safe to repeat the journey to the edge on foot.
On the walk out he noted that his footprints had been eradicated by the night wind. Peering cautiously over the edge in the pale morning light he could see the shelter resting partially buried about one hundred meters below. The shell had broken open. There was no sign of the mast. Sam reported what he saw to the Rollagon in a matter-of-fact tone, dictating for the official record. The sighting of the shelter had closed the matter as far as he was concerned. He had turned and started back when the AI suggested that he should descend and recover the AI carapace.
"The carapace is irreplaceable and possibly still usable. It would be best to recover it, if only to determine what happened here."
After looking over the lip and seeing the effort that would be required, Sam was unconvinced that the benefits were worth the risks. "We don't need to recover it to know what happened here. The area is unstable and let go. End of line. They never should have put it so close to the edge."
"After all", he said impulsively, "it's just memory." He caught himself, somewhat surprised at this insensitivity and then even more surprised at his surprise. On the return to the Rollagon he thought it over. The whole edge was probably unstable. It was risky, but if he was careful, probably relatively easy and safe. He would need a few tools and lots of rope.
"OK, we'll give it a try."
He strapped on the utility tool belt that doubled as a swiss seat, re-checked his consumables and headed back. At the newly formed edge he tossed the end of the rope down and turned around. At the end of his drooping lifeline he could see the Rollagon. He leaned back against the tension and, controlling with a hand pressed to his hip, rappelled down the first meter or so. As his head drew level with the edge, he could see streamers of sand and dust just above the surface, dislodged by the taut safety line. A pebble ticked off his visor, causing him to flinch instinctively. Then he pushed off and rappelled down the drop. He landed softly.
The regolith was loose and he sunk in until his boots were covered. The dirt was dry, but in the faint light of early morning, it was still flecked with ice and showed signs of recent wetness. He backed down the slope in what he judged to be the direction of the wrecked shelter, keeping tension on the rope. He was almost past it when he caught sight of it on his right. He tried a few sideways leaps but after almost losing his balance, decided a shuffle would serve him better. In a few moments of awkward scrambling he was there.
The shelter had torn open at one end. The airlock was missing, having been completely ripped off. Peering into the darkness, he could see that both equipment racks were gone too, wrenched from the floor. The AI rack and carapace were still in place, though the rack leaned at a crazy angle. He needed help here, and he called the AI for instructions.
"The carapace must be disconnected from the cooling and signal cables. It is quite simple. Then the carapace must be unbolted from the rack using a 15 mm Torx wrench."
The cables were easy. The coolant cables emitted a red spray before they sealed, and the signal cables were FO and popped open when pushed and turned in one motion. The bolts were another matter altogether. In the poor lighting, feet off kilter and restricted in every sense by the suit and the cramped confines of t
he shelter, it was a difficult and time consuming task to remove them. And of course, one of them, the one in the least accessible location, wouldn't come loose.
Unable to bend sufficiently in the suit, he found it necessary to lie on the floor on his side to reach the bolt. Finally, with a grunt he hoped could be heard by the AI, he brought it loose.
He lay for a while on the tilted floor catching his breath, sweat running down into his eyes. When he recovered, he clambered to his knees and pulled the carapace free of its mount. It was surprisingly light—probably less than twenty kilos. He placed it on the floor. It slid across on the sand-covered surface and thumped against the side of the shelter. He looked around. Nothing else was salvageable.
He carried the carapace outside and set it down on the shelter wall. Looking up the steep slope he wondered how in the hell he was going to carry it while pulling himself up. It was obvious that the AI would have to winch him.
They discussed it briefly, and in a few moments Sam saw the rope go tight. He leaned back and walked up the slope, cradling the carapace in both arms. There were a few close moments at the top when his head drew even with the edge. Stopping there, he tossed the carapace onto the surface, then leaned back and walked/crawled up the face, scrambling over the edge on his knees and pulling on the rope with his hands to get over the last of it. He rolled onto his side, looking up at the pink sky, gasping for air, resting, listening to the kindly advice of the suit.
The whole thing had taken only thirty minutes but Sam was exhausted. He could have stayed there flat on his back for hours but the AI broke his reverie, urging him to bring the carapace to the vehicle. Obediently, Sam clambered to his feet. The AI met him with an extended manipulator arm and whisked the carapace up and out of sight. He watched it go, then sat down in the shade of a Rollagon wheel and leaned back. Sweat was still running into his eyes. His heart was pounding. The suit murmured in his ears.