Middle School Students Investigate the Science Behind a Comet

Why does a comet have a tail? WAB Middle School students explored that question by creating their own comet from ice, organic matter, and dust, watching it change, and using physics and chemistry to explain what they observed. The ingredients were carefully chosen to mirror a comet’s composition: water, ethanol, ammonia, and dry ice for its different ices; corn syrup for organic matter; and rock and dust collected from the MS garden. As the dry ice sublimated, changing directly from solid to gas, a thick white cloud rose from the surface, giving students a visible model of the material that forms a comet’s coma and tails. 

“When we put the materials together, you could really see it changing. The cloud that came off it made it easier to imagine how a comet can have a tail.” Kaiya, Grade 7 

“It changed what I thought because I didn’t know comets were made of ice and other materials like ammonia. I thought they were kind of like asteroids — just rock. The experiment taught me that they might look a little alike, but they are made of very different things.” Lilou, Grade 7 

Students saw first-hand how comets behave differently from planets and asteroids. Understanding why requires them to grapple with complex physics and chemistry: thermal energy, gravity, solar radiation, solar wind, and the way a comet’s icy nucleus heats as it approaches the Sun. As its ices sublimate, gas and dust escape to form a cloud around the nucleus called a coma. Radiation pressure and the solar wind then push that material away from the Sun, creating a dust tail and an ion, or gas, tail.

Building a model forces students to move past memorizing that sequence and into actually understanding it. Why a tail? Why does it grow? What is the comet made of, and what does each ingredient in our model represent? 

“We used dry ice, dirt and water, and put everything together to make something like a comet. When we moved it with the tweezers, the smoke from the dry ice made a tail. It was fun and memorable, but it was also learning — so you remember what comets are made of and how they work.” - Cyrus, Grade 8 

This experience is an example of how units at WAB are designed as connected chapters in a bigger story. The sublimation students witnessed becomes an anchor point when they reach the chemistry unit later in the program. When they meet states of matter and phase changes again, they will be building on something they saw, made, and were genuinely wowed by. 

The comet build gives that abstract comparison a physical, memorable form. In this unit, students are comparing gas giants, rocky planets, asteroids, and comets side by side. They are thinking like planetary scientists, weighing evidence about composition, behavior, and the forces acting on each body. This is what learning looks like at WAB: challenge and wonder, with students handling real materials, using real science vocabulary like “sublimate” because they need the word to describe what they just watched, and making connections across units.