0 meters deep (492 feet). Some craters
have a round central pit surrounded by ragged, ejected
material, while others have a flat floor and straight sides.
The diameter of one large crater, called Left Foot, is one
fifth of the surface of the comet. Left Foot is one kilometer
(.62 miles) across, while the entire comet is only five
kilometers (3.1 miles) across.

"Another big surprise was the abundance and behavior of jets
of particles shooting up from the comet's surface. We expected
a couple of jets, but saw more than two dozen in the brief
flyby," said Dr. Benton Clark, chief scientist of space
exploration systems, Lockheed Martin Space Systems, Denver.

The team predicted the jets would shoot up for a short
distance, and then be dispersed into a halo around Wild 2.
Instead, some super-speedy jets remained intact, like blasts
of water from a powerful garden hose. This phenomenon created
quite a wild ride for Stardust during the encounter.

"Stardust was absolutely pummeled. It flew through three huge
jets that bombarded the spacecraft with about a million
particles per second," said Thomas Duxbury, Stardust project
manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif.
Twelve particles, some larger than a bullet, penetrated the
top layer of the spacecraft's protective shield.

The violent jets may form when the Sun shines on icy areas
near or just below the comet's surface. The solid ice becomes
a gas without going through a liquid phase. Escaping into the
vacuum of space, the jets blast out at hundreds of kilometers
per hour.

The Stardust team theorizes sublimation and object hits may
have created the comet's distinct features. Some features may
have formed billions of years ago, when life began on Earth,
Brownlee said. Particles collected by Stardust during the Wild
2 encounter may help unscramble the secrets of how the solar
system formed.

Stardust was launched in 1999. It is zooming back to Earth
with thousands of captured particles tucked inside a capsule.
The capsule will make a soft landing in the Utah desert in
January 2006. The samples will be analyzed at the planetary
material curatorial facility at NASA's Johnson Space Center,
Houston.

Comets have been objects of fascination through the ages. Many
scientists believe they delivered carbon and water, life's
building blocks, to Earth. Yet their destructive potential is
illustrated by the widely h