Iapetus (spelled Japetus[1] in Arthur C. Clarke’s 2001: A Space Odyssey) is a moon of Saturn where an anomalous signal was first broadcasted in the Jovian system.


In 1999, a last minute directive is fed to HAL 9000 that once in the Jovian system, Discovery is to change course and go to the Saturn’s moon system via a gravitation slingshot off of Jupiter. The secret directive changes the mission parameters to: investigate an anomalous signal traced to Saturn’s moon, Iapetus.

In the film adaption, once the Discovery arrives to the Jovian system, the mission objective (TMA-2) suddenly appears in space, in the proximity of Jupiter's moon Io.[note 1]

  1. The monolith signal originally detected at Saturn’s Iapetus in the novel, and then suddenly appearing at Jupiter’s Io in the film—fits rather well in the mythology of the space odyssey monoliths: appearing where they want, when they want, and multiplying themselves at any given time.
  1. Arthur C. Clarke’s 2001: A Space Odyssey (Read PDF)


The following events are considered a ‘variation universe’ suggested in Arthur C. Clarke’s 2061 forward.

In the 2001 novel, a monolith (TMA-2), similar to the Tycho Monolith on Earth's moon, is traced to Saturn’s moons Japetus. The mission to Japetus is known by HAL 9000, but is kept secret from David Bowman until the climax of the story.

When Bowman discovers the new mission objective, he spends months on Discovery, alone, preparing to rendezvous with Japetus. He notices a small black spot on Saturn’s moon. When he gets closer, he realizes that this is an immense black slab, similar to TMA-1, only much larger. He takes one of the extra-vehicular pods in an attempt to land on the monolith. The slab, which had been inert for so long, opens and is full of stars. It swallows Bowman's pod and disappears from Japetus. Mission Control never hears from Bowman again.[spark 1]


  1. Spark Notes, 2001: A Space Odyssey, novel Summary
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