Solaris is a Polish science fiction novel by Stanisław Lem (1921-2006), published in Warsaw in 1961 and is his best known work in English translation. While the narration suggests that humans study the planet, the opposite seems to be the case, where the titular alien planet, Solaris, examines the secret and often guilty thoughts of human beings. These secrets and thoughts are given physical form on the space station which orbits the planet. The novel is pervaded by a powerful and moving poetic sense of remoteness and loneliness.
The novel is about the ultimately futile attempt to communicate with an alien life-form on a distant planet. The planet, called Solaris, is covered with a so-called "ocean" that seems to really be a single organism covering the entire surface. The ocean shows signs of a vast but strange intelligence, which can create physical phenomena in a way that science has difficulty explaining. The alien mind of Solaris is so inconceivably different from human consciousness that all attempts at communication are doomed (the "alienness" of aliens was one of Lem's favourite themes; he was scornful about portrayals of aliens as humanoid).
The novel begins with the arrival of the protagonist, Kris Kelvin, at a scientific research station hovering above the surface of Solaris. Research has been ongoing for years, but scientists have been unable to do more than observe the highly complex phenomena on the surface of the ocean, all the while classifying them into an elaborate nomenclature without understanding what they actually mean. When the protagonist and his colleagues become more aggressive in trying to force contact with Solaris, the experiment becomes psychologically traumatic for the researchers themselves. The ocean's response, such as it is, lays bare their own personalities, while revealing nothing of the ocean's. To the extent that the ocean's actions can be understood, the ocean begins experimenting with the researchers' minds by confronting them with their most painful and repressed thoughts and memories through the materialization of complex human constructs: the protagonist is confronted with memories of his deceased lover and his guilt over her suicide. What torments the other researchers is only hinted at (as they are careful to conceal it) but it appears to be much worse.
Andrei Tarkovsky's film follows the novel loosely, emphasizing human relationships over Lem's theories on exobiology, and devoting a substantial amount of time to Kelvin's life on Earth before his trip to Solaris. In 2002, Steven Soderbergh made a film adaptation of Solaris which focuses on the relationship between Kelvin and his deceased wife to the exclusion of many of Lem's other themes.
Rheya is Kelvin's deceased wife, who died from a lethal injection after a fight with Kelvin. She appears as his visitor. The first Rheya who appears is lured by Kelvin into a shuttle due to his overwhelming fear and then the shuttle is ejected into the space. Her fate is not known, but when Snow suggests they hail the shuttle to discover her fate, Kelvin objects. Rheya reappears rather soon, the same as at first and unaware of the event with the shuttle. However, the "second" Harey (or as Lem/Kelvin rephrased "repeated Rheya") becomes aware of her transient nature, and becomes haunted by the fact that she is a tool employed by Solaris to some unknown effect on Kelvin. After hearing a tape recording by Gibarian and discovering her true nature, she attempts to kill herself by drinking liquid oxygen. She fails, because her new Solaris-created body is built of unknown matter and is of unknown structure. She is eventually killed by Snow, at her request, using a device developed by Sartorius meant to disrupt the sub-atomic structures of the constructs (and prevent them from reappearing).