Comets, Meteors, and Asteroids

What’s the difference between comets, meteors, and asteroids?


A comet is a big frozen chunk of ice and rock that orbits the sun or another star or zooms madly around space until pulled into the orbit of a star.  As they near a star they get heated and bits of them fall off, leaving a trail of debris.

Notice that the tail of the comet always faces away from the sun. The solar wind blowing at the comet determines the direction of the tail. Image by Fredrick, Wikimedia, released into the public domain.

As the earth and other planets orbit through the path of a comet, they are rained down on by this debris and other rocks and stuff floating in space.


The rocks that rain down on us are called meteors.  If those chunks are large enough to survive passing through the atmosphere and make landfall we call them meteorites.

Photo by Jacek Halicki, CC license, Wikimedia.


An asteroid is a hunk of rock ranging from pebbles to bodies as large as several hundred miles across that orbits the earth.  Most asteroids are in the asteroid belt between Mars and Jupiter.

This is the asteroid Gaspra. It was photographed by the Galileo spacecraft in 1992. Image by NASA, public domain.

 Scientists think that they are debris that couldn’t form into a planet because of the amount of gravity exerted by nearby Jupiter, but we can’t be sure, especially as we’re not really sure about how planets form in the first place.

This is an artist’s concept of an event that might have happened in the early formation of the solar system. Did the asteroid belt form because of colossal crashes like this one? It seems likely, but no one knows for sure. Image by NASA, public domain.

Make A “Comet”

Make a comet using dry ice, sand, and water.  Wear gloves when handling dry ice.  An adult should do the actual handling of the dry ice.

How to make a model comet with dry ice.

  1. Crush a small block of dry ice (about a pound).  Put it in a couple layers of heavy plastic and hit it with a hammer.
  2. Add a handful of sand to the dry ice and mix it in.
  3. Add a cup of water to the bag.
  4. Using your hands (in thick gloves) shape the ice into a ball.  If it won’t clump together, add more water.
  5. Take it out of the bag and place on a safe surface, like on a cutting board or in a metal pan.


  • the definition and parts of a comet: nucleus (head), coma, and tail.
  • what a comet is made of (ice, rock, metal, and possibly some organic material)
  • how a comets tail always flies away from the sun.
  • scientists think comets originate in the Kuiper belt, out beyond Neptune or further in the Oort Cloud, but they can’t really be sure.
  • meteors are bits that have fallen off of comets.
  • meteor showers happen when earth passes through the path of a comet.
  • comets orbit the sun or other stars.

Additional Layers

  • Edmund Halley studied comets during his life.  One of the most famous comets is named after him, Haley’s comet.
  • Just before William of Normandy sailed to England to do his conquering in 1066, he sighted Haley’s comet, and deemed it a good omen.  The comet sighting is recorded in the Bayeux Tapestry.
  • More meteorites hit at the poles than anywhere else on earth.  Why?
  • Eleanor Helin studied asteroids, photographing hundreds of them with an observatory telescope.  Most of what we know about asteroids is because of her work.
  • Learn more about natural satellites in Unit 1-4 of the Layers of Learning curriculum.
Unit 1-4 has lots more about satellites, natural and man-made.
Unit 1-4 has lots more about satellites, natural and man-made.


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