Make Your Own Comet

Main Content

DIY Experiment Series Asks: What is a Comet Made of?

The "How To" From Science-U


  • Soy Sauce
  • Dry Ice
  • Ammonia
  • Water
  • Potting Soil
  • Ziplock bag
  • Fabric gloves
  • Lightbulb/hot light source
  • Hammer


  1. Place a cup of potting soil in a plastic bag.
  2. Add a tablespoon or so of each of the ammonia and the soy sauce.
  3. Add a handful of broken-up dry ice (be sure to have your gloves on!)
  4. Smash and mix the materials in the bag until they form a comet clump.
  5. Hold your comet in front of a "sun" (the light) and watch its "tail" as the dry ice evaporates.

For educators and parents - How to guide young learners in science:

  • Inquiry-based learning (IBL) is a teaching approach that is fundamental for the development of higher order thinking skills (summarizing, analyzing, evaluating, creating). It puts the student in the driver's seat and promotes learning through engaging student-based investigations, following the same process used by scientists.
  • IBL begins by posing a question, problem, or scenario rather than simply presenting facts or a standard method to solve a problem. The learner is actively engaged and investigates concepts to reach authentic meaning.
  • The IBL process can vary, however the basics are as follows:

1. The student creates a testable question of their own.

2. The student obtains supporting evidence to answer the question by making observations, doing research, collecting data through an experiment, changing variables from a previous experiment, etc.

3. The student explains the evidence collected.

4. The student creates a claim (explanation) and justifies it using evidence form the investigation.

5. The student creates predictions for future investigations.

  • Recording information during the IBL process is also important to promote science literacy. The following chart is a helpful tool to guide students through the process.

Guided inquiry map

Questions to ask:

  • What is sublimation and what does it have to do with this experiment?
  • What is dry ice made of? Why does it release "smoke"?
  • What happens to the comet if you leave it set for 30 minutes? 3 hours? 24 hours?
  • Where are real comets found?

The Science Behind It:

The potting soil represents the dust floating in outer space that has come together to form the comet. The ammonia and soy sauce represent organic matter. The dry ice represents the cold temperatures freezing all the space matter together. As a comet orbits the sun, it begins to disintegrate and the sun illuminates those particles falling off--creating the "tail" we see.


Looking for more cool Astronomy activities?

Click here to check out our DIY tutorial for a spectrometer!


Here is what the final product will look like and the spectra you might see with yours!


  • Teaching Great Lakes Science (
  • Special thanks to Comet Animation courtesy of the European Space Agency (Esa)
Register Button