The Invincible by Stanislaw Lem

the sun’s rays could not penetrate to the bottom. Even the bright cones of their searchlights were swallowed up by the gloomy abyss.
    “Tell me, Ballmin, what is that damned jungle supposed to be?” asked Rohan once more. He was furious. He had kept rubbing the sand off his face and now his forehead was reddened, his skin smarted, his eyes were burning. On top of it all he would shortly have to make his next report to the crew back at the spacecraft. He had no idea how he could describe what they had encountered here.
    “I’m not a clairvoyant,” replied the scientist. “I’m not even an archeologist. Not that an archeologist could tell you a great deal here either. It seems to me—” Suddenly he fell silent.
    “Go on. Finish what you were going to say.”
    “This doesn’t look like any dwelling or the destroyed houses of any humanoid creatures. Do you see what I mean? The only thing I could compare it to would be a machine of some kind.”
    “A machine? What type of a machine? A computer, maybe?”
    “What gives you that idea?” countered the planetologist laconically. The robot made a left turn. It was flying close to the metal poles which were jutting out from the bent slabs. Several times the robot almost touched the crazy black network.
    “No, no electric circuits to be seen. Or did you notice any switches? Insulators? Anything that might be part of an electronic brain?”
    “Maybe they weren’t fireproof. There could have been a fire here. After all, this is nothing but ruins,” replied Rohan. But his voice lacked conviction.
    “Who knows? Maybe you’re right,” admitted Ballmin unexpectedly.
    “But what should I tell the astrogator?”
    “Why don’t you let him see for himself and transmit the whole deal here by television?”
    “That can’t have been a city,” said Rohan, suddenly summarizing his thoughts about what he had seen here.
    “Most likely not,” agreed Ballmin. “At least not the kind of city we know. Nothing that corresponds to our notion of what a city should be like. No human beings, nothing resembling us could have dwelled here. And since the life forms we found in the ocean here were similar to those back home on Earth, it would be logical to assume the same thing for any living organisms on the mainland.”
    “Yes, I keep racking my brains. None of the biologists will commit himself to make a statement. What do you think about that?”
    “They don’t want to talk about it, because it simply seems too improbable, as if something had prevented life from becoming established on land; as if the aquatic creatures had never been permitted to leave the water.”
    “There might have been some reason for that—a nearby supernova explosion, for example. The Zeta of the Lyre constellation is known to have been a nova several million years ago. Organic life on the continents may have been annihilated by radiation, while life survived in the deeper regions of the ocean.”
    “If there had ever been radiation, we would still be able to find traces of it, but there is practically no radioactivity in the soil of this part of the galaxy. Aside from the fact that evolution would have moved ahead during the several million years since. You wouldn’t expect any vertebrates on land, of course, but the more primitive forms should be present. Didn’t you notice the total absence of any life forms in the littoral zone?”
    “Yes, I did. But what does that mean?”
    “A great deal. Life usually originates in the shore regions of the oceans, and migrates to deeper waters only afterwards. It can’t have been any different here. Only something must have chased it away from the edge of the sea. Something must be preventing it from going on land.”
    “What basis do you have for your conclusions?”
    “The fact that the fish were frightened by our probes. On all the other planets I have known, animals were never afraid of machines. They are not afraid of things they have never seen