Einstein Science Reporting for Kids
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18-Jun-2004

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How close can you get to a comet?



Wild 2's surface is pockmarked with craters. Image courtesy of Donald Brownlee; NASA.
Click here for a high resolution photograph.

In January 2004, the Stardust spacecraft came breathlessly close to a comet named Wild 2. Instruments on board snapped close-up images and sampled the particles swarming around the comet's solid center as the spacecraft inched past the comet.

(The spacecraft was actually 236 kilometers away, but that's still remarkably close for a comet.)

Comets are frozen balls of gas, dust and larger particles that contain some of the most ancient ingredients of the solar system. The solid center is called the "nucleus" and the debris floating around the nucleus is the "coma."

This close comet encounter has provided a wealth of information about Wild 2, sent from the spacecraft back to scientists on Earth. The spacecraft also collected particles from the coma and will return them to Earth in a protected sample capsule in 2006.



If you have the blue and red glasses that you use to watch 3-D movies, you can use them on this photo to see Wild 2 in 3-D. Image courtesy of Donald Brownlee; NASA.
Click here for a high resolution photograph.

A large team of researchers now describes the preliminary results from this mission in a special section of the 18 June issue of the journal Science.

The images reveal that the nucleus' surface has lots of craters formed by impacts from other space objects. This means that the comet's interior is probably made of something fairly strong. If the comet were just a loose rubble pile or fragile ice ball, it wouldn't have held together during the impacts.

As the spacecraft traveled through the haze of particles in the coma, the scientists were surprised to find that the clouds actually consisted of small, distinct particle swarms. These bursts of activity may be related to larger chunks of the comet breaking up.

Scientists also detected 20 narrow jets of gas and dust, streaming out of spots on the surface of the nucleus.

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Download video of Wild 2. [2.17 MB, 20 seconds]
3-D glasses will also work with this video clip.
[Video courtesy of Donald Brownlee]

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