Floyd follows a suggestion that he simply try to call Bowman on the radio, and later has a strange dream in which he sees a small monolith floating at the foot of his bed. During the flight, the celebrity passengers discuss the mystery surrounding Dave Bowman and the monoliths, and whether they would be allowed to land on Europa to rescue the crew of the Galaxy crew.

After siphoning water from Halley's vents to refuel, an idea conceived by Universe's navigation officer and advanced by Floyd, Universe heads directly for Europa. Universe abandons its exploration of Halley to rescue Galaxy. Observing the burgeoning aquatic life forms of Europa, the crew pilots Galaxy to an island that they name Haven. Failing in her (unexplained) plan, she commits suicide, and the crew of the Galaxy crew are stranded. As Galaxy nears Europa, Rosie, a stewardess, attempts to hijack the craft, forcing it to crash into Europa's ocean. He communicates his discovery to his uncle Paul Krueger, and van der Berg is also invited to join the crew of the spacecraft Galaxy for its flyby of Europa. On Ganymede, Rolf van der Berg, a second-generation Afrikaner refugee, studies data on satellite surveys of Mount Zeus and forms an astonishing thesis about its nature. The Universe lands on Halley, and the crew explore its surface and its caves. Now, at the age of 103, Floyd is chosen as one of six 'celebrity guests' to travel aboard the privately owned spaceliner Universe for the first-ever human landing on the surface of Halley's Comet as it again nears Earth. His estranged grandson, Chris II, works aboard the spacecraft Galaxy. Heywood Floyd, the protagonist of 2010, has had an accident and become a permanent resident of an orbital space hospital. On Earth, a period of relative peace has evolved between the United States, Soviet Union, and China, although a non-violent revolution has taken place in South Africa (now the United States of Southern Africa or USSA) the white population has fled to Europe, taking most of the country's wealth with them and leaving the black population to rebuild the economy, which they do in a matter of weeks thanks to the country's diamond mines. But humanity is wary of sending spacecraft close to Europa despite its fascinating mysteries, including the appearance of a large mountain, dubbed 'Mount Zeus', on its surface. Large-scale interplanetary travel is now commercially viable with muon-catalyzed fusion-powered spacecraft.

The new sun, dubbed 'Lucifer', has transformed the moons of the former Jupiter: Io has become a volcanic hellhole, Europa an ocean world shrouded by clouds, and Ganymede a temperate world that the human race is colonizing. The opening chapters of 2061 gradually explain the events that have taken place in the interim years. ALL THESE WORLDS ARE YOURS-EXCEPT EUROPA.

Space odyssey novel