A warning was sent from Earth, to the effect that the scientist-explorers should expect to have to deal with more than one of these slave-machines. Caution should be exercised. The warning was superfluous. Something approaching a hundred cigar-shaped machines had already surrounded the laboratory. The urgent question now was whether the mission could extricate itself at all. On every side a mass of shining metal could be seen. Gradually, almost cautiously, the machines began to close in, a foot or two at a time, in a kind of slow, shuffling movement.
There was nothing to be done except run for it. The men waited until the gleaming monsters were quite close. At first it didn’t seem too bad, because in the weak gravity of Mars they could jump clean over the brutes. The machines responded as if it were only some kind of game. Instead of each machine searching separately for the men, the things worked in a team, apparently in accord with some master plan. They sought to block each of the men, working on data from the sound waves generated in the ground by the men in their flight, or so it seemed. Certainly the machines were not equipped with apparatus sensitive to light. They could not see. When the men stopped, the machines stopped. But as soon as a man took a single step, the machines glided into some new pattern.
Four of the men made it, three did not. From the safety of the module, the four lucky ones watched in horror as each of the three was cornered, hemmed in by packed lines of machines which could not be jumped. The things built a quadrangle about each man in turn. One machine went into the quadrangle along with the man. The last desperate struggle took a long time, but always it ended the same way, with the man pushed over, sprawling on the ground. The machine rolled over on top of him, but with a door open. The unfortunate victim found himself precipitated into the quite smooth capsule inside the monster. Inevitably, the door closed. The machine with the prize in its belly then began its journey to the depths below. The other machines opened out to make a way for it. The thing moved to a middle distance. Suddenly it tilted and disappeared.
All this came out after the return of the residue of the third Martian mission. NASA didn’t like it. Nobody liked it. Everybody felt the expedition should have been armed with nuclear weapons. Yet NASA could hardly be blamed for its failure to anticipate the existence of developed Martians. Cognizant biologists had expected only to collect a few bugs or, at best, a few primitive plants.
Preparations were put in hand to plug a batch of nuclear weapons into the surface of Mars. After considerable argument, however, it was decided to wait awhile. For one thing, it wasn’t clear how the Martians, deep below their glaciers, could be harmed by surface explosions. For another, the Martians hadn’t really done anything explicitly hostile. Certainly four perfectly sound citizens had been creamed. Yet look at it from the other side for a moment. Four perfectly sound Martians had probably been sucked up through the borehole drilled by the third mission. Squirting Martians into the atmosphere in the style of a soda siphon would naturally be viewed in a grave light by the other side. Surely it would justify an examination of the situation, even to the extent of hunting down one or two of the strange creatures that had suddenly appeared out of space. We ourselves would hardly have acted in any other way. Whichever way you looked at it, nuclear weapons wouldn’t have much effect, not a kilometer or two down.
The telepuppets came into their own at this stage. They were set to watch the Martian surface by electronic camera. A stream of pictures was telemetered to Earth. It soon appeared that remarkable changes were in hand. Large structures appeared, very like radio antennae. It made sense when you came to think about it. Perhaps for millions of years the Martians had lived under their glaciers without experiencing any visitation from outside. Possibly from time to time they had taken a look at the external world, finding little of interest. It was very different now, however. At last there had indeed been a visitation from outside, and the Martians were determined to find out, what the hell. NASA had succeeded, at fantastic expense, in stirring a hornet’s nest.
Yet there was nothing to worry about when the first signals came through. Attempts were made to decode them, of course, but without the slightest success. Somebody had the amusing idea of setting up a closed loop. There seemed no possibility of it doing any harm. Signals from Mars were fed directly into a terrestrial computer, the output from which was fed back to a terrestrial transmitting antenna, back to Mars. Nobody expected much to come of it, but everybody hoped for something more than a simple return of the original message. Small changes, in fact, appeared after a few days. The terrestrial computer was not returning exactly the same signals as the ones which were being fed into it. This meant the home computer was acting as an outpost for the Martians, although of course in an apparently harmless way. The Martians must have discovered something of the home computer’s function and of its basic design.
The next step was to investigate what was going on. It was necessary now to work the closed loop through the home computer with a man-made program inside it. So the loop was set up in parallel with a straightforward mathematical problem. It was a simple matter of time-sharing, the computer being used for two apparently quite distinct purposes, much as one can run two distinct human problems in the same computer at the same time. Whereas the human problems stay distinct, however, these did not. The Martian loop stopped the mathematical problem. There wasn’t any mystery about how this could happen. The Martians stopped the mathematics in exactly the same way we ourselves would do, by instructions to the computer from without. There was no difficulty about it and apparently no harm either. Indeed, it was all very encouraging, since it implied a small area of contact with the Martians. Further experiments were tried out with varying success. Other kinds of human program were used. Chess, in which the Martians took not the slightest interest, business accountancy and general data-processing, language translation, and so forth, traffic-flow problems. A lot of stuff was put on tape and the Martians were left to sort it out as best they could.
Two things occurred in quick succession. The computer started to work in earnest, in a very different fashion from its earlier sporadic behavior. Instructions were inserted for a print-out of the contents of the computer, but the print-out proved to be on a hopelessly vast scale. There was no possibility of detecting any sense in it. The other thing was that pictures from the telepuppets ceased. A meteorite might have hit one of them, but the whole lot could hardly have been hit all at exactly the same time. The Martians had evidently knocked them off, there could be no other explanation.
Preparations for meeting an invasion from Mars were now put seriously in hand. The nuclear defense capability was weighed and not found wanting. There seemed no grounds for alarm. Nobody thought to break the computer link with Mars. The link was indeed thought of as an advantage, since it could eventually give a lead to the purposes and the nature of the Martians.
The invasion came without any notice at all. The stuff was sprinkled into the terrestrial atmosphere as if from a cosmic pepper pot. The Martians treated chemistry rather as humans treat electronics, something to be worked out by rational calculation, not a subject for crude empiricism. With their vast calculating resources, the properties of complex molecules could be definitively worked out. So they knew exactly what they were doing when the stuff was sprinkled into the terrestrial atmosphere. It took the best part of three months for it to settle to ground level and to get into water supplies all over the Earth. Then there was the devil to pay. The birth rate fell to zero within a few more weeks. The human species suddenly found itself completely sterile, in fantastic contrast to its previous cornucopian fecundity. The chemical makeup of the bodies of the unfortunate scientist-explorers had given all the necessary data. The determination of a complete inhibitor of human fertility had then been a straightforward, if somewhat tedious job.