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Our Glaciers: Then and Now activity kit helps you see the changes taking place in glaciers around the world. See all our activity kits and classroom activities.
This is an image of Comet Kohoutek.
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Not too long ago, many people thought that comets were a sign that something terrible was about to happen. People didn't understand about how objects in the sky moved, so the sight of a comet must have been very scary.

Now we know that comets are lumps of ice and dust that come flying into the solar system from deep space, and that some comets make repeated trips. Jets of gas and dust form long tails that we can see from Earth. These tails can sometimes be millions of miles long.

Unfortunately, we don't get to see comets very frequently. In 1985-1986, a spacecraft called Giotto visited the most famous comet of all, Halley's comet. In 1994, a comet named Shoemaker-Levy, ran into Jupiter!

In 1996 and 1997, we could see comet Hyakutake, and comet Hale-Bopp from Earth. Hale-Bopp was one of the brightest comets ever seen from Earth. Comet Linear was discovered in 1999 and came closest to the Sun in July 2000. The Stardust spacecraft flew by Comet Wild 2 in January 2004, collecting samples of the comet to return to Earth. The newest comet mission is Rosetta and it will land on a comet named Churyumov-Gerasimenko

Now scientists have identified a class of comets known as small comets (though they originally were just called snowballs from space!).

How would you like build your own comet? Now you can, with our interactive comet animation. Check it out!

Last modified February 25, 2004 by Randy Russell.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA