Asteroid (4179) Toutatis to Pass Closely By Earth on Wednesday, September 29, 2004

Toutatis, a potato-shaped asteroid about 4.6 km (3 miles) in its longest extent, will pass within 1,550,000 km (963,000 miles) of the Earth’s center on Wednesday, September 29, 2004 – reaching its closest approach at 13:35:28 GMT (06:35:28 PDT). This is roughly four times the distance from the Earth to the moon and closer than this asteroid has come to Earth since at least the twelfth century. Toutatis will not pass this closely again for the next 500 years. The passage is the closest Earth approach this century for a known asteroid of this size. Because of an extensive set of optical and radar observations, the orbit for Toutatis is one of the best determined of any asteroid and there is no chance that this object will collide with the Earth during this encounter – or any other encounter for at least 5 centuries.

With the help of Toutatis radar observations, a shape and rotation model for this object has been developed. Details on this work by Steve Ostro, R. Scott Hudson and colleagues can be found at:

http://www.eecs.wsu.edu/~hudson/Research/Asteroids/4179/

Simulations of the asteroid’s rotation in space can be found at:

http://reason.jpl.nasa.gov/~ostro/ToutatisHires.mov
http://reason.jpl.nasa.gov/~ostro/ToutatisHires.avi

Diagrams by P.W. Chodas (JPL/Caltech)

The two diagrams above show the circumstance of the asteroid flyby of the Earth. The first shows an oblique view of the flyby at the time of closest approach, with the Moon’s orbit drawn in for scale. Toutatis approaches the Earth from the right in this diagram, passing from outside the Earth’s orbit to inside on a path that passes beneath the ecliptic plane (the plane of the Earth’s orbit). The second diagram is an edge-on view showing how Toutatis passes the Earth well under the ecliptic plane, which is shown as a straight line. Again, the Moon’s orbit is shown for scale; note that it is slightly inclined to the ecliptic plane.