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 held theory that a comet or asteroid wiped out the dinosaurs.

To view Stardust images on the Internet, visit:  http://stardust.jpl.nasa.gov or http://photojournal.jpl.nasa.gov/

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