Comet Model - a Space Themed Dry Ice Science Experiment

When we saw that dry ice can freeze dirt during our volcano science experiment, we knew that creating a comet model needed to be on our list of dry ice science projects! Plus, we love astronomy for kids and do a space theme one or two times a year!

Before we made the actual comet model we talked about what comets are made of. I told the kids that we know comets have rocks, dust, frozen water, frozen carbon dioxide (and other gasses), and organic material (like amino acids and nucleic acids). I asked them to think of what they wanted to represent a comet and we would go outside and build our comet model. Here's what they came up with:

What are comets made of? - What we used in our model!

rocks - rocks

dust - dirt

frozen water - water (the dry ice would freeze it)

frozen gasses - dry ice (frozen carbon dioxide)

organic matter - crushed leaves

organic matter - vinegar

organic matter - any other random thing they could find

(I think I saw an orange peel and grape stem...)

I think our favorite part was that real comets have dry ice in them too...it made us feel a little like astronauts as we put together our little comet models!

Awesome Dry Ice Experiment:

To start out with, we crushed the dry ice (frozen carbon dioxide) and put it in a bowl. We used an old orange bowl we had left over from Halloween. It's good I was not attached to it because all the crushing and mixing and temperature changes cracked it in a few spots!

SAFETY NOTE: Remember never to touch dry ice with your bare hands! We used tongs, a hammer, and big spoons.

Next we mixed all of our ingredients together EXCEPT the water and vinegar. I encouraged the kids to add those last because the dry ice would freeze them and they would help glue all the other ingredients together.

Finally, we added the water and vinegar in a slow drizzle and used spoons to press the comet ball together.

Little sections froze quickly, but it only took about five minutes for our nice big comet model to be ready!

We carried it around the yard a bit to simulate a comet orbiting the sun. This was a great time to talk about benefits and limitations of models. For example, we can't make a "dirty snowball" (as comets are sometimes called) that will orbit on its own. But, we can watch how the right forces and ingredients (dry ice) can make liquid water, dirt, and organic matter all harden together into an icy ball like a comet.

This, of course led to a few other questions, like...

Why do comets have a tail?

When the icy comet gets close to the sun, solar radiation and solar winds knock off, blow, and melt enough ice and dust that it looks like a tail falling off the comet. Most of the tail is water vapor.

What are the parts of a comet?

A comet has three basic parts: the nucleus, coma, and tail. The nucleus is the compact center of the comet. When it gets close to the sun, water vapor and dust make rise off the comet making a sort of atmosphere called a coma. As the coma gets hit with solar winds and radiation from the sun, water vapor and dust blow behind the comet, forming a tail.

Where do comets come from?

Most comets come from either the Kuiper Belt or the Oort Cloud. The Kuiper Belt begins after Neptune and is full of icy rocks (including dwarf planets like Pluto). The Oort Cloud is beyond the Kuiper Belt and is expected to be full of cometary nucleuses orbiting at the farthest reach of our solar system. Generally, we expect comets that take more than 200 years to orbit to come from the Oort Cloud.

Are there comet names?

Yes! Comets have been seen for thousands of years and were historically named after the year they were seen (like the Great Comet of 1680) or people (like Ceasar's Comet or Halley's Comet). Comet Swift-Tuttle was named after two separate astronomers who discovered it on their own a few days apart. Comets are still named after people, but the International Astronomical Union also has a numbering system that they use to label all comets too.

In the end, we left our comet model on an outdoor table. The next day it had melted into a small pile of rock, dirt, and organic matter, which was all recycled back into our garden.

I thought I would end with a few fun comet facts... because I think think they're fun! ;)

1- The nucleus of most comets is 1-2 miles across!

2- Comet Hale-Bopp in 1995 was visible to the "naked eye" longer than any other comet: 19 months!

3- Every 76 years Halley's Comet passes through our solar system, leaving a trail of dust, ice, and rocks. Every year, when Earth's orbit passes through that debris (usually in October), pieces of it burn up in our atmosphere, making lots of "shooting stars" that we call the Orionids meteor shower!

4- In 2014 the spaceship Rosetta's lander Philae actually landed on Comet 67P! In 2016 Rosetta itself also crash-landed on the comet, ending a historic 12-year mission! Learn more here.

Want to save this idea for later? This picture is "pin ready!!":

We had a blast making our dry ice comet model! I would love to hear from you if you try this fun science experiment, too! Feel free to email me, leave a note, or visit my Facebook page (Preschool Powol Packets) and share your experience with this dry ice science project.

You can also check out our other dry ice experiments here: