The Invincible

by Stanislaw Lem

A heavily-armed interstellar spacecraft called Invincible lands on the planet Regis III, which seems uninhabited and bleak, to investigate the loss of her sister ship, Condor. During the investigation, the crew finds evidence of a form of quasi-life, born through evolution of autonomous, [[self-replicating machine]]s, apparently left behind by an alien civilization ship which landed on Regis III a very long time ago.

The protagonists come to speculate that a kind of evolution must have taken place under the selection pressures of "robot wars", with the only surviving form being swarms of minuscule, insect-like micromachines. Individually, or in small groups, they are quite harmless and capable of only very simple behavior. When threatened, they can assemble into huge clouds, travel at a high speed, and even to climb to the top of the troposphere. These swarms display complex behavior arising from [[self-organization]] and can incapacitate any intelligent threat by a powerful surge of electromagnetic interference. Condor's crew suffered a complete memory erasure as a consequence of attacks from these "clouds". The swarm, however, is reactive. It lacks intelligence and cannot proactively formulate attack strategies.

Invincible's crew mounts an escalating series of attacks on the perceived enemy, but eventually recognizes the futility of their efforts. The robotic "fauna", dubbed "necrosphere", has become part of the planet's ecology, and would require a disruption on a planetary scale to be destroyed.

In the face of defeat and imminent withdrawal of the Invincible, Rohan, the spaceship's first navigator, undertakes a trip into the "enemy area" in search of four crew members who went missing in action – an attempt which he and the Invincible's commander Horpach see as certainly futile, but necessary for moral reasons. Rohan wanders into canyons covered by metallic "shrubs" and "insects", and finds some of the missing crewmen dead. He gathers some evidence and returns to the ship unharmed, thanks partially to a device that cloaks his brain activity and partially to his calm and nonthreatening behavior. Rohan expresses his intention to petition for preservation of the planet's artificial ecosystem, which fascinates him.