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Toutatis's eccentric, four-year orbit, illustrated here by JPL's Near-Earth Object Program Office, extends from just inside the Earth's orbit to the main asteroid belt between Mars and Jupiter. The plane of Toutatis's orbit is closer to the plane of the Earth's orbit than any other known several-kilometer Earth-orbit-crossing asteroid, or ECA. It is in a 3:1 mean-motion resonance with Jupiter that serves as a dynamical pathway from main-belt orbits to Earth-crossing orbits on time scales of a million years. Toutatis may have the most CHAOTIC orbit studied to date, a consequence of the asteroid's frequent close approaches to Earth.

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Even with the mass known, however, there will still be much that is unknown about the interior, and therefore the history, of Toutatis. In particular, Ostro believes that "there's probably no way of knowing" whether Toutatis is one funny-shaped asteroid or two asteroids touching "until we send a human crew." There are no current plans for that, but "because it's in the plane of the Earth's orbit it's a good target. Who knows, maybe some time in this century, people will go there." Humans will certainly be keeping a close eye on Toutatis. Its orbit is well enough known that it's safe to say it won't hit the Earth anytime soon. But "it's in the ecliptic, so it makes a lot of close approaches. Chances are EXCELLENT that it will collide with the Earth someday."

These are radar images of asteroid 4179 Toutatis made during the object's recent close approach to Earth on December 8, 1992. The images reveal two irregularly shaped, cratered objects about 4 and 2.5 kilometers (2.5 and 1.6 miles) in average diameter which are probably in contact with each other. The four frames shown here (from left to right) were obtained on Dec. 8, 9, 10 and 13 when Toutatis was an average of about 4 million kilometers (2.5 million miles) from Earth.