Dry ice is combined with water, dirt, and other ingredients to make a model comet. The mixture forms an icy clump that produces jets of gas when exposed to light and heat, simulating how real comets behave near the sun.

1. Put on gloves and goggles for safety.
2. Crush dry ice into small chunks and powder using a mallet, keeping at least half as powder.
3. Line a large plastic bowl with a heavy plastic bag.
4. Add 1 liter of water, about 2 cups of dirt, and small amounts of starch, corn syrup or soda, vinegar, and rubbing alcohol to the bowl.
5. Stir ingredients together and mix in the crushed dry ice. Observe the white cloud that forms.
6. Gather the bag sides and press the mixture into a clump. Add water as needed until it holds together.
7. Remove the clump from the bag to show the “comet.” Measure its mass and record data.
8. Observe gas jets escaping from the comet surface.
9. Shine a flashlight (the sun) and blow warm air from a hairdryer (solar wind) onto the comet to simulate heating and tail formation.
10. Re-measure the comet’s mass at 5-minute intervals as it melts, up to 30 minutes. Record results.

Create a Comet With Dry Ice - NASA Video:

📄 Create a Comet With Dry Ice - NASA Jet Propulsion Laboratory: https://www.jpl.nasa.gov/edu/resources/lesson-plan/create-a-comet-with-dry-ice/

• Compare comet stability with different ratios of water to dry ice.
• Use less ingredients to make a smaller comet.
• Use a balance scale to measure more precisely how the comet’s mass changes over time.

• Always wear goggles and thick gloves when handling dry ice.
• Keep students at a safe distance during crushing and mixing to avoid flying pieces of dry ice.
• Do not touch dry ice with bare skin—it causes frostbite on contact.
• Work in a ventilated area to prevent carbon dioxide buildup.
• Never store dry ice in a sealed container; pressure can cause explosions.
• Dispose of the comet by placing it in a sink to melt safely.

• How does dry ice sublimate differently from water ice as the comet warms?
• What do the dirt, starch, syrup, vinegar, and alcohol represent in a real comet?
• Why do comets develop tails when they get close to the sun?
• How does the comet’s mass change over time, and what does this simulate about real comets?