[meteorite-list] How to make a Kitchen Comet -----------O

From: Rick Nowak <internationalmeteoritesociety_at_meteoritecentral.com>
Date: Thu Apr 22 10:02:24 2004
Message-ID: <20020302133015.79343.qmail_at_web21008.mail.yahoo.com>

How to make a Kitchen Comet

You can make an accurate model of a comet nucleus
easily and inexpensively. Unfortunately it is
difficult to do neatly.
Here is what you need:

1. Five pounds of dry ice. You can get this from ice
companies or ice cream parlors. CAUTION: Dry ice is
-79 degrees C (-110 degrees F). Any more than a brief
exposure will cause 'burns". Be careful when handling
it.
2. Water: Around half a gallon in a pitcher.

3. Ammonia: A few drops or sprays of window
cleaner.

4. Dirt: Fine grained, about one handful.

5. Corn Starch or Worcester Sauce: Just a couple of
pinches or drops.

6. Trash Bags: Two large bags.

7. Large Bowl or Small Pot

8. Water Proof Gloves: The better insulated the warmer
your hands will remain.

9. Cloth Towel.

10. Paper Towels: One small roll is plenty.

11. Hammer.

12. Mixing Spoon or Stick.
These ingredients are either actual components or
handy analogous ones. The dry ice is frozen carbon
dioxide. Water, ammonia, organic (carbon based)
molecules, and silicates are all present on comet
nuclei. They have been identified through spectral
measurements of comet tails and the collection of tiny
ice particles by very high flying research aircraft.
Here is the Recipe:
Line the bowl with a trash bag. Place the other trash
bag on the floor. Pour about a pint of water into the
bow. Add the corn starch or Worcester sauce, ammonia,
and some of the dirt. Mix a bit.
Put on the cloves. Wrap the dry ice in CLOTH towel.
Place it over the trash bag on the floor. Use the
hammer to grind up the dry ice into a powder.
Gradually poor the dry ice powder into the water,
mixing as you poor. There will be lots of vapor
formed. The dry ice, water and other ingredients
should form a thickening slush. Keep stirring for a
few seconds as it thickens.
Now, using the trash bag to lift the slush away from
the sides of the bowl, use your gloved hands to pack
the slush into a ball. Keep packing and forming until
the ball solidifies as a big lump.
Peel back the trash bag. Scatter some more dirt over
the lump. Pour some of the remaining water over the
lump, turning as you do so, so that a layer of water
ice forms over the entire lump.
Observe the behavior of your miniature comet nucleus.
It can be handled without gloves if the water ice
coating is intact. If a spot feels sticky, pour water
on the spot. It hisses and pops as carbon dioxide
sublimes (goes from the solid state directly into a
gas) and forces its way through weak spots in the
water ice crust. On real nuclei this results in
slight jetting forces that can cause the nucleus to
spin, slightly alter its orbit, or spit apart (or
"calve").
Note: Get about three or four pound of dry ice for
each nucleus you plan to make. You can purchase it
the afternoon or evening prior to the demonstration
and store it in a freezer or ice chest. Place an inch
or so of newspaper below the cry ice to prevent
cracking to the surface on which it rests. Try the
demonstration first to an idea of the correct amounts
of water to use.
It's fun, it's a mess, and it's one of the most
memorable and scientifically accurate demonstrations
in astronomy!


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Received on Sat 02 Mar 2002 08:30:15 AM PST