2010: Odyssey Two

''This article is about the 1982 novel, 2010: Odyssey Two. For the 1984 film, see 2010: The Year We Make Contact''

2010: Odyssey Two  is a 1982 science fiction novel that serves as the sequel to 2001: A Space Odyssey, authored by Arthur C. Clarke.

Plot
2010: Odyssey Two follows the adventure of Heywood Floyd to Jupiter, to investigate the Discovery.

Synopsis
The story is set nine years after the failure of the Discovery One mission to Jupiter.

A joint Soviet-American crew, including Heywood Floyd from 2001, on the Soviet spaceship Leonov (named after the cosmonaut) arrives to discover what went wrong with the earlier mission, to investigate the Monolith in orbit around the planet, and to resolve the disappearance of David Bowman. They hypothesize that much of this information is locked away on the now-abandoned Discovery One. The Soviets have an advanced new "Sakharov" drive which will propel them to Jupiter ahead of the American Discovery Two, so Floyd is assigned to the Leonov crew.

However, a Chinese space station rockets out of Earth orbit, revealing itself to be the interplanetary spacecraft Tsien, also aimed at Jupiter. The Leonov crewmembers think the Chinese are on a one-way trip due to its speed, but Floyd surmises that due to the large water content of Europa they intend to land there and use the water content to refuel. The daring mission of the Tsien ends in failure, when it is destroyed by an indigenous life-form on Europa. The only survivor, Professor Chang radios the story to the Leonov; it is presumed that he dies when his spacesuit air supply runs out.

The Leonov survives a dangerous aerobraking around Jupiter and arrives at Discovery. Mission crewmember and HAL 9000's creator, Dr. Chandra, reactivates the computer to ascertain the cause of his earlier aberrant behaviour. After some time, Floyd is speaking to a Russian on board, who, for an instant, sees the Monolith open again, into a Stargate, as David Bowman escapes from the Monolith's dimension back into ours.

A sequence of scenes follows the explorations of David Bowman, who has been transformed into a non-corporeal, energy-based life-form, much like the aliens controlling the monoliths. During his journey, the avatar of Bowman travels to Earth, making contact with significant individuals from his past: He visits his mother and brushes her hair (shortly before she dies), and he appears to his ex-girlfriend on her television screen. In the novel, the aliens are using Bowman as a probe to learn about humankind. He then returns to the Jupiter system to explore beneath the ice of Europa, where he finds aquatic life-forms, and under the clouds of Jupiter, where he discovers gaseous life-forms. Both are primitive, but the aliens deem the Europan creatures to have evolutionary potential.

An apparition of Bowman appears before Floyd, warning him that they must leave Jupiter within fifteen days. Floyd has difficulty convincing the rest of the crew at first, but then the monolith vanishes from orbit.

The Leonov crew devises a plan to use the Discovery as a "booster rocket", enabling them to return to Earth ahead of schedule. HAL and the Discovery will be trapped in Jupiter's orbit, with insufficient fuel to escape. The crew are worried that HAL will have the same neuroses on discovering that he will be abandoned yet again, so Chandra must convince HAL that the human crew is in danger.

The Leonov crew flees Jupiter as a mysterious dark spot appears on Jupiter and begins to grow. HAL's telescope observations reveal that the "Great Black Spot" is, in fact, a vast population of monoliths, increasing at an exponential rate, which appear to be eating the planet. By acting as self-replicating machines, these monoliths increase Jupiter's density until the planet achieves nuclear fusion, becoming a small star. In the novel, this obliterates the primitive life forms inhabiting the Jovian atmosphere, which the Monoliths' controllers had deemed highly unlikely to ever achieve intelligence, unlike the aquatic life of Europa.

As Jupiter is about to transform, Bowman returns to Discovery to give HAL a last order to carry out. HAL begins repeatedly broadcasting the message

ALL THESE WORLDS ARE YOURS – EXCEPT EUROPA. ATTEMPT NO LANDINGS THERE.

The creation of the new star, which Earth eventually names Lucifer, destroys Discovery. However, in appreciation for HAL's help, Bowman has the aliens which control the monoliths remove HAL's artificial intelligence from the computer core of the Discovery and transform him into the same kind of life form as David Bowman, and become his companion.

Epilogue
The book ends with a brief epilogue, which takes place in AD 20,001. By this time, the Europa have evolved into a species that has developed a primitive civilisation, most likely with assistance from a monolith. They are not described in detail, though they are said to have "tendril"-like limbs. They regard the star Lucifer (formerly the planet Jupiter) as their primary sun, referring to Sol as "The Cold Sun". Though their settlements are concentrated primarily in the hemisphere of Europa which is constantly bathed in Lucifer's rays, some Europans have begun in recent generations to explore the Farside, the hemisphere facing away from Lucifer, which is still covered in ice. There they may witness the spectacle of night, unknown on the other side of Europa, when the Cold Sun sets.

The Europans who explore the Farside have been carefully observing the night sky and have begun to develop a mythology based on their observations. They correctly believe that Lucifer was not always there. They believe that the Cold Sun was its brother and was condemned to march around the sky for a crime. The Europans also see three other major bodies in the sky. One seems to be constantly engulfed in fire, and the other two have lights on them which are gradually spreading. These three bodies are the moons Io, Callisto, and Ganymede, the latter two of which are presently being colonised by humans.

Humans have been attempting to explore Europa ever since Lucifer was created in 2010. However, none of these attempts has been successful. Every probe that has attempted to land on Europa has been destroyed on approach. The debris from every probe falls to the surface of the planet, and the debris from some of the first ships to be destroyed is venerated by the Europans.

Finally, there is a Monolith on the planet, which is worshipped by the Europans more than anything else. The Europans assume, correctly, that the Monolith is what keeps humans at bay. Dave Bowman and HAL lie dormant in this Monolith. The Monolith is the guardian of Europa, and will continue to prevent contact between humans and Europans for as long as it sees fit.