A mountain-sized asteroid will make its closest approach
to Earth at 9:35 a.m. EDT tomorrow.

Although asteroid 4179 Toutatis will come no closer than four
times the distance between the Earth and the moon
(approximately 961,000), this will be the closest approach of
any known asteroid of comparable size this century.

“This is the closest Toutatis will come for another 500
years, and its orbit is very well known,” said Dr. Don
Yeomans of NASA’s Jet Propulsion Laboratory (JPL), Pasadena,
Calif., manager of NASA’s Near Earth Objects Program Office.
“What this fly-by provides is an opportunity to study one of
our closest solar system neighbors,” he said.

“While we have done radar observations on this particular
asteroid before, this is the closest it has come since at
least the twelfth century ” said Dr. Steve Ostro, a scientist
at JPL. “We will use the huge dish in Arecibo, Puerto Rico,
to refine our knowledge of its physical characteristics and
its trajectory,” he said.

Named after an obscure Celtic and Gallic god, Toutatis, the
yam-shaped space rock measures 1.92 kilometers (1.2 miles) by
2.29 kilometers (1.4 miles) by 4.6 kilometers (2.9 miles).
Toutatis has one of the strangest rotation states observed in
the solar system. Instead of spinning around a single axis,
as do the planets and the vast majority of asteroids, it
“tumbles” somewhat like a football after a botched pass. Its
rotation is the result of two different types of motion with
periods of 5.4 and 7.3 Earth days that combine in such a way
that Toutatis’s orientation, with respect to the solar
system, never repeats.

When the asteroid flies past Earth, it will be traveling at
approximately 39,600 kilometers per hour (24,550 mph).
Toutatis has not passed this close to Earth since the twelfth
century, and it will not be this close again until 2562.
Toutatis was discovered in 1989.

Arecibo Observatory is operated by Cornell University,
Ithaca, N.Y., under a cooperative agreement with the National
Scie

nce Foundation, with support from NASA.

To view a computer model of asteroid Toutatis on the
Internet, visit:
http://reason.jpl.nasa.gov/~ostro/ToutatisHires.mov

and

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

For more information about near Earth objects on the
Internet, visit:
http://neo.jpl.nasa.gov/

For information about NASA on the Internet, visit:
http://www.nasa.gov