Crater Creations: Moon
In the 30–45-minute Crater Creations: Moon activity, teams of children ages 8 to13 experiment to create impact craters and examine the associated features. The children observe images of lunar craters and explore how the mass, shape, velocity, and angle of impactors affects the size and shape of the crater.This activity has been modified from Impact Craters, an activity in Exploring the Moon: A Teacher's Guide with Activities for Earth and Space Sciences, NASA Education Product EG-1997-10-116-HQ by J. Taylor and L. Martel. The guide offers a math- and graph-rich version of this activity.
What's the Point?
- Impact craters are caused when an impactor collides with a planet or moon.
- A crater's size and features depend on the mass, velocity, and incoming angle of the impactor.
- Impact craters provide insights into the age and geology of a planet's surface.
- Models — such as those the children are using here — can be tools for understanding the natural world.
For each team of 3 to 5 children:
- A large pan or box such as a dish pan, aluminum baking pan, or copy paper box lid (larger pans allow children to drop more impactors before having to resmooth or resurface)
- Enough sand, sugar, rice, or oatmeal to fill the pan about 4 inches
- Enough flour to make a 1"- to 2"-deep layer
- 1 heaping cup of powdered cocoa
- A sifter
- A large trash bag or piece of cloth or plastic to place under the crater box
- Several objects that can be used as impactors, such as large and small marbles, golf balls, rocks, bouncy balls, and ball bearings. Use your imagination!
- Paper and pencil
- Images of lunar craters
- Safety glasses
For the facilitator:
- Print out the images of lunar craters.
- Prepare an area large enough to accommodate the crater boxes for the number of teams participating. Allow several feet between each box.
- Prepare the appropriate number of crater boxes:
- Fill a pan 4 inches deep with sand, sugar, rice, or oatmeal.
- Add a 1- to 2-inch layer of flour.
- With the sifter, sprinkle a thin layer of powdered cocoa on top of the flour (just enough to cover the flour).
- Provide several impactors, a ruler, and images of craters beside each box.
1. Show the images of lunar craters to the children and invite them to describe what they see.
- What shape are they?
- How can they use the light and shadow to determine the shape and features of the craters?
- Can they find some craters on top of each other? Which were formed first? Which were formed later? Do the edges of the more recent craters look different than those of the older ones?
2. Divide the children into groups of 3 to 5 and have each group stand by a box. Invite them to begin experimenting by having them each select one impactor to drop and determining from what heights they will drop them (encourage them to not throw their impactors). What do they think will happen when an impactor — a heavy object — is dropped into one of the boxes? Have each team drop their impactors one at a time.
- What do they observe?
- Does the feature that was created look like any of the features they observed on the surface of the Moon? They look like craters — roughly circular depressions on the surface of a planet or moon.
- How are they similar? Different? Some similarities include the circular shape and depression, and the material that is excavated from the crater and forms a rim — the ejecta. Long bright streaks — rays — probably extend out from the crater they created. Some differences include the fact that the impactor is still present in the model.
After each crater creation, ask them to carefully remove their impactors to make the craters clearly visible. (In reality, impactors are completely — or almost completely — obliterated upon impact; any remains of the impactor are called "meteorites.")
3. Now, taking turns, let the children experiment with creating craters! Have each group conduct an experiment by changing one variable to see how it affects impact crater size. Experiments could explore different impactor sizes, weights, distances dropped, or angles of impact. For example, one group could drop the same impactor from different heights (modeling different velocities of the incoming impactors), and another group could experiment by dropping different-sized impactors from the same height. If the children want to experiment with angles of impact they will need to throw the impactors at the box; caution should be used to make sure no one is standing on the opposite side of the box in case the impactors miss. Invite the children to predict what will happen in their experiments. Have the children measure and note the width and depth of each impact crater formed in their experiments.
- What did the groups observe?
- How did the weight of objects affect the size and depth of the crater you created?
- How did the size of the object affect the size and depth of the crater?
- How did dropping or throwing the impactors from different heights affect the sizes and depths of the craters they formed?
Have the children reflect on what they observed and the images of lunar craters.
- What features did the children create in their models? Impact craters.
- How do the children think the craters on the Moon formed? By large impactors — asteroids or comets — striking its surface.
- Scientists have not actually seen any large asteroids or comets hit the Moon, but they think the large craters on the Moon — and on other planets and moons — were created by them. Scientists have observed very small asteroids hitting the Moon and Earth, and they observed several pieces of Comet Shoemaker-Levy striking Jupiter. NASA's Lunar CRater Observation and Sensing Satellite mission will intentionally impact the Moon's south pole with a used rocket and the spacecraft itself in fall 2009. Scientists will study the debris plume that is thrown up from the impact.
- When the children see "shooting stars" — more accurately called "meteors" they are seeing tiny dust- to sand-sized "asteroids" that are streaking toward Earth's surface. They are too small to make craters or leave any meteorites to collect.
- What evidence might scientists have to make them think impactors created the craters in the lunar crater images? Scientists experiment with models — like the children did — to determine what type of feature an impactor might leave behind. They also have other evidence from some craters on Earth: fragments of the asteroids (meteorites) and alterations to the rocks and minerals at the impact sites caused by the impactors striking the ground at high speed.
October 16, 2009