Recipe for a Moon
The Moon is made of cheese... no! Rice Krispies treats! Children ages 8 to 13 discover that the Moon, like Earth, is made up of layers of different materials through this 45-minute activity. They work in teams to make models of the interiors of the Moon and Earth. Common food items are used to construct the cores, mantles, and crusts of both planetary objects.
What's the Point?
- Models can be tools for understanding the natural world and for helping us to identify more questions.
- The planets are made of solids, liquids, and gases.
- The solid Earth is layered with a solid surface crust; hot, convecting solid mantle; and dense, metallic core. Its gaseous atmosphere is thin compared to these layers.
- The Moon is made of similar materials as Earth's crust.
For the group:
- Optional: butcher paper, newspapers, or disposable table cloths for the activity area
- Wet wipes or damp paper towels
- Additional plates for eating the treats, if desired
- Global images of Earth and the Moon
- Books about the Moon
- Art supplies, such as colored pencils, crayons, and markers
- A Peek into the Moon's Interior
For each team of two to four children (or for each individual child if you prefer that they make their own Earth and Moon):
- 5 Rice Krispies Treats®
- 1 donut hole
- 1 cinnamon candy (e.g. Red Hots)
- tsp. hot cocoa mix
- 1 tsp. powdered sugar
- 2 tablespoons of red icing
- 2 teaspoons green sprinkles in a baggie
- 4 teaspoons blue sprinkles in a baggie
- 10–12 mini chocolate chips
- 6 regular-sized chocolate chips
- 3 Zip–loc® baggies
- 1 small cups
- 1 ruler
- 1 spoon
- 1 plastic knife
- 1 cardboard plate
- Recipe for the Moon and Recipe for Earth
For each child:
- Recipe for a Moon comic panel
- His/her Marvel Moon comic book and binder clip
- 1 pencil or pen
- Optional: 1 copy of instructions for making an edible Moon at home
For the facilitator:
You may need to modify this activity for children with dietary restrictions.
- Review the background information.
- Place the different colors of sprinkles in separate baggies. Place the mini- and regular-sized chocolate chips in separate baggies. Place the icing in a small cup.
- This is a fun, but messy activity! If possible, tell the children ahead of time to wear an old shirt or apron, or you may wish to provide trash bags for them to wear.
- Display several books about the Moon in a place where the children can page through them before and after the activity.
- If desired, provide copies of instructions for making an edible Moon at home with their families.
1. Introduce the activity by dividing the children into teams of three to four and explaining that each team will create edible models of the Moon and Earth. Invite them to share what they know about the Moon:
- How do Earth and the Moon compare in size? Which is bigger?
- Does Earth have layers inside? Can they name some of those layers?
- What is the inside of Earth like? Children may say there is a molten layer under the surface; this is an important misconception that will be examined in the activity.
- Imagine you could cut the Moon in half with a knife and look at it insides. Does the Moon have layers inside? What might they be like?
Remind them of their earlier findings about how the Moon formed from the Wham! Moon! activity. They modeled how the debris from the Giant Impact came together — accreted — into our Moon using Play-Doh. They saw that the Earth and Moon were made of similar materials.
- Do you think Earth and the Moon look similar on the inside?
2. Before you begin, explain to the children that this is a fun and tasty — but messy — activity! Have them wash their hands before they start and remind them to not lick their fingers while they are working on their models. For now, they will just make the model — they will be invited to eat them at the end of the activity! Provide the food materials and recipes to each team.
3. Create a model of the Moon! Provide the materials to the teams and invite them to follow the recipe for a Moon.
- Moon's inner metallic core: 1 cinnamon candy
- Moon's mantle: 1/4 Rice Krispies Treat
- Moon's crust: hot cocoa mix mixed with powdered sugar
Have each team tear one off about one quarter of a Rice Krispies Treat and set aside the rest for Earth's continental crust. Have them place the cinnamon candy in the middle of the treat and gently wrap the treat around it. Form it into a ball, rolling it around to make it firm.
- Ask the children to compare the size of the mantle and core. What do they notice? The mantle is very thick compared to the small core.
Invite the children to create the Moon's dusty surface. Roll the treat in the hot cocoa and powdered sugar mix.
4. Create a model of Earth! Provide the materials to the teams and invite them to follow the recipe for Earth.
- Earth's inner solid metallic core: a donut hole
- Earth's molten (liquid) outer core: red icing
- Earth's mantle: 4 Rice Krispies Treats
- Earth's oceanic crust: blue sprinkles or "jimmies"
- Earth's continental crust: 3/4 Rice Krispies Treat covered in green sprinkles or "jimmies"
Mash four Rice Krispies Treats together so they make one "mega treat." Have them form the treat into a flat rectangle, about 4 inches by 6 inches. Starting in the center of the flattened "mega treat," smooth a thin sheet of the red icing to within one inch of each edge; they should use about half of the icing and save the rest for later. Place the donut hole in the middle. Gently wrap the Rice Krispies Treats around the donut hole — with the icing side against the donut hole — to form a ball. Roll it around and squeeze it to make it firm.
Invite the children to add continental and oceanic crusts to their "Earths." Have them place their Earth spheres in the baggie with the blue sprinkles. Roll it around until it is thoroughly covered in blue. Remove and set it aside.
- Ask the children what they think the blue represents. Many of the children may say "the ocean." Clarify that in this model we are using blue to represent the thin crust under the ocean (oceanic crust).
Now invite them to make the continental crust — the land on Earth. Ask them to take the Rice Krispies Treat half they set aside earlier and flatten it into a thin layer. Have the children create four or five continent shapes, then gently press one side of each continent into the green sprinkles until covered. Have them gently press each continent onto the Earth sphere with the sprinkle side up. In reality, the thicker continental crust does not "sit" on top of the oceanic crust; both sit above the Earth's mantle.
- What do the green sprinkles represent? The crust, or land, that is above the ocean (the thicker continental crust).
5. Invite the children to compare their models to the global images of Earth and the Moon.
- Which is larger? Earth.
Ask the children to remember the Earth and Moon's long history from the activity Time Travelers. Many of the event cards described processes that changed their surfaces to form the features we see today.
Facilitator’s Note: Physical processes have been at work during the 4.5-billion-year history of Earth and our Moon.
Early in its history, Earth formed continental and oceanic crusts. Through time, geologic processes changed the surface to form the familiar pattern of continents and oceans we observe today. Early in Earth's history, volcanos spewed gases — including water vapor and carbon dioxide — into the atmosphere. When things cooled down enough the water vapor condensed as liquid water in our oceans.
While the Moon never had oceans or an atmosphere or shifting plates to alter its surface, it did experience some of the same processes that altered Earth's surface: volcanism and impacts by asteroids and comets.
The heat from accretion caused the Moon, or at least its outer layer, to melt, creating a magma ocean. Eventually the crust cooled. For the first 600 million years of its existence, large asteroids continued to strike the Moon and the planets in our solar system, perhaps in waves of intense bombardment, creating the large basins and craters we see on the Moon. By 3.8 billion years ago, much of the "debris" in the solar system had been swept up into the planets and their moons, corralled into the asteroid belt, or relegated to the outer reaches of our solar system, and impact strikes were smaller and less frequent.
While cool on the outside, the interior was still hot. Molten rock would still rise to the Moon’s surface and break through cracks or erupt at volcanos. The lava filled the basin and crater floors — the low areas on the Moon. It cooled quickly, forming fine-grained, dark, volcanic rocks called basalt; basalt is the most common type of volcanic rock we find Earth. When you look at the Moon, you can see the large, somewhat circular, dark basins. These are the basalt-filled ancient impact basins. In spite of this exciting beginning and history, the Moon has been geologically inactive for at least the last billion years.
- What features do you see on Earth? Oceans and continents.
- What features do you see on the Moon? Large circular features — impact craters — and areas of light grey and dark grey.
- Which would have more impact craters, the Moon or Earth, and why? The Moon has more impact craters because the only thing that will wear them down are more impacts! On Earth, weather, water, earthquakes, lava flows, and life erode or cover impact craters. Old crust is destroyed and new crust formed through plate tectonics.
- Does Earth have volcanos? Yes. Does the Moon have volcanos? Accept all answers.
- What makes volcanos? Molten rock or magma coming from inside the planet.
- If the rock is melted, what does this mean about the temperature of the planet? It is hot enough to melt the rock!
- Earth has lots of active volcanos — like the volcanos of Hawaii and Mount St. Helens in Washington State What does that mean about Earth's inside? Earth is very hot.
- On the Moon, we see evidence of lava flows — lava filled the bottoms of the huge impact basins on the Moon — but there are few volcanos and they are no longer active. What might this tell us about the Moon? The Moon was once hot enough for molten rock to flow on its surface.
- How might they make their Earth and Moon more realistic? Their answers may include adding these features.
Invite the children to create craters in the crusts using their fingers. Fill in the largest impact basins on the Moon with regular-sized chocolate chips — pressed tip-down into the treat — to form the dark-colored regions, or maria, on the Moon.
Invite the teams to add mini chocolate chip volcanos to their Earth models. They may want to use the left-over red icing to help the chocolate chips stick.
Facilitator Note: At this scale, the chocolate chips — even the minis! — are really much too large!
- What does the red icing represent? Melted or molten rock, or magma under the volcano.
- Is there a layer of melted rock under the Earth's crust in their model? No, just little pockets. This is an important point to make, as children often think there is a melted layer under Earth's crust that feeds magma to volcanos. If there were a molten layer everywhere, we might expect to see volcanos everywhere!
- Is there a melted layer anywhere in Earth — did they use the red icing for any layer? Yes, the red icing was used for the outer core. Earth's outer core is molten.
- Is there a melted layer anywhere on the Moon? No, the Moon model has only solid layers. The dark rocks that fill the basins are evidence that the Moon’s interior was hot in the past.
Explain that scientists are still investigating the Moon's core. Further studies may show how large it is and whether it is liquid or solid.
6. Have the children spend a few minutes talking in their groups about what the inside of their the Moon and Earth models will look like if they cut them open. Invite them to draw their predictions if they wish.
7. Return to their models and have the teams carefully cut both the Moon and Earth in half. Small children may need help cutting, and they may need to reshape the planets after cutting.
8. Invite the teams to examine the cross sections of their planets and draw what they see, comic-book style, in their Recipe for a Moon comic panel. Show them the Sneak Peek into the Moon's Interior and ask them to label the layers in their drawings with the terms: crust, mantle, and core, including a note about Earth's inner and outer core. Instruct the children to add the Recipe for a Moon comic panel as the next page in the Marvel Moon comic book by clipping the book together at the upper left corner.
- Were their predictions correct about the interiors of Earth and the Moon? Do the insides look like the children thought they would?
- What do the different layers represent? Refer to steps 3 and 4.
- In what ways are the interiors of the Moon and Earth similar? They both have layers, with a central core, a middle mantle, and an outer crust. They both have volcanic rock on their surfaces.
- Are they made of similar materials? Yes!
As the children saw in Wham! Moon!, pieces of Earth mixed with pieces of an impactor to come together — accrete — to form the Moon.
- In what ways are they different? Earth has a layer of icing that represents the liquid molten outer core. Earth has a solid inner core.
The cores of the Earth and Moon are both metallic. The Moon's core is much smaller relative to its size, when compared to Earth. This is one line of evidence that supports the Giant Impact hypothesis. The small planetary body struck Earth in a glancing blow, which stripped part of the outer layers of the impacting object and Earth to form the Moon. Earth's dense core was left intact, and the core of the small planetary body was absorbed by the Earth. The Moon was born with much less iron and other heavy elements to form its core.
Facilitator’s Note: The children may have many misconceptions about Earth's interior. They may believe the crust floats on a molten layer, but as modeled in this activity, only the outer core is liquid. Pieces of Earth's crust do move on top (giving rise to earthquakes), but they are riding a layer of solid — but ductile — rock.
Share with older children that Earth's molten layer of material — iron and nickel — is very important. Convection (flow) of material in Earth's outer core creates Earth's magnetic field. This magnetic field protects us from dangerous particles from the Sun called solar wind. Without a magnetic field, these particles would wear away our atmosphere and dangerous radiation from the Sun would reach Earth's surface.
The Moon does not have a magnetic field like Earth's. Without this protective magnetic field, dangerous radiation reaches the Moon’s surface.
- In general, Earth has two different types of crust — thick crust where there is land (continental crust) and thin crust under the oceans (oceanic crust). On the Moon, the crust is thick everywhere.
- How do these models represent the Moon and Earth? Their overall sizes and the thicknesses of their layers are approximately to scale. Each layer is made of different materials.
- How do they not represent the Moon and Earth? They are smaller and made of different materials than real planets.
Add that scientists dont yet have accurate measurements on the diameter of the Moon's core, thickness of the mantle, and depth of the surface.
9. Discuss how scientists study the surface and interior of the Moon.
- How do the children think scientists study the surface of the Moon? The children may have ideas about studying rocks or taking pictures of the landscape. They may know that spacecraft collect data from orbit around the Moon. They may recall that during the Apollo mission, the astronauts conducted experiments on the lunar surface and brought rocks back to Earth.
Spacecraft take photographs of surface features and measure how their orbits are affected by the Moon's gravitational pull. Instruments left on the lunar surface by Apollo astronauts measured moonquakes and revealed clues about the organization of the Moon's interior. Moon rocks brought back by the Apollo missions changed how scientists thought about the Moon's formation and changes over time. It was only by examining those rocks that they hypothesized the Moon must have formed from the Earth's crust through a giant impact. Some rocks were formed in the mantle and brought to the surface during the Moon's ancient volcanic period, and others were thrown out of deep holes (craters) created by ongoing impacts. Using computer models, scientists now have a better idea of how the Moon's interior settled into layers after the giant impact. Future missions, such as NASA's Gravity Recovery and Interior Laboratory - GRAIL — mission will collect data to help scientists better understand the Moon's interior.
Invite the children to eat the treats while they consider how Earth and the Moon are similar and how they are different. Invite them to consider the similarity of the Earth’s mantle and the Moon's as they bite the Rice Krispies treats.
- Do they prefer their chocolate "lava flows" as low, flat plains, like on the Moon, or spread out as volcanos across the surface, like on Earth?
- What do they think scientists will learn about the Moon's "cinnamon candy" core after the GRAIL mission sends more information about the Moon back to Earth?
Invite the children to attend the next program, Growing Up Moon, to investigate how the Moon’s long history of impact cratering and volcanism created the surface features we see today.