This activity has been modified from Lava Layering, 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. (http://www.spacegrant.hawaii.edu/)
In the 30-45 minute Crater Creations activity, teams of children ages 8-13, experiment to create impact craters and examine the associated features. The children observe images of Martian craters and explore how the mass, shape, velocity, and angle of impactors affects the size and shape of the crater.
What's the Point?
- Impact craters are caused when an impactor collides with a planet.
- 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 the children are using here — can be tools for understanding the natural world
- Geologists use features on Earth to help them understand how similar features may have formed on other planets, like Mars.
Materials
For each child:
For each team of 4-8 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 re-smooth 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!
- Ruler
- Paper and pencil
- Images of craters from the Setting the Scene activity
- Safety glasses
For the Facilitator:
Preparation
- 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 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
Activity
1. Introduce the activity by asking the children what they think will happen when an impactor — a heavy object — is dropped into one of the boxes.
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 select one impactor to drop and determining from what height they will drop it (encourage them to not throw their impactor). What do they think will happen? Have each teams drop their impactor 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 Mars or Earth?
- Which features? Craters — roughly circular depressions on the surface of a planet.
- 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. Some differences include the fact that the impactor is still present in the model. Long bright streaks — rays — probably extend out from the crater they created; these also occur in some places on Mars and the Moon.
After each crater creation, ask them to carefully remove their impactor, to make the crater 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 impactor misses. Invite the children to predict what will happen in their experiment. Have the children measure the width and depth of each impact crater formed in their experiment.
- 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 size and depth of the craters they formed?
Conclusion
Have the children reflect on what they observed and the images from Mars and Earth. Invite them to record what they learned in their GSI Journals.
- What features did the children create in their models? Impact craters.
- Do similarly shaped features occur on Mars or Earth? Yes, both.
- How are they different? The craters on Mars are much, much larger.
- How do the children think the craters on Mars and Earth formed? By large impactors — asteroids or comets — striking the Earth and Mars.
- Scientists have not actually seen any large asteroids or comets hit Mars, but they think the large craters on Mars — and on other planets and moons — were created by them. Scientists have observed very small asteroids hitting Earth and several pieces of Comet Shoemaker-Levy struck Jupiter. 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 these craters? 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 — like fragments of the asteroid (meteorites), or alterations to the rocks and minerals at the impact site caused by the impactor striking the ground at high speed.
Invite the children to reflect on what they learned during all of their different investigations.
- How might observations on Earth help scientists interpret what they see on other planets? Scientists study features — like volcanos — on Earth to understand their shape and size, what they are made of, and how they form. On Earth, this information can be used to predict where volcanos may form, and when they may erupt. By understanding volcanos on Earth, scientists can interpret what they see on other planets. If they see a feature that is similar in shape and detail to volcanos on Earth, even if the volcano is not erupting, they can interpret that it is a volcano — and this tells them about the history of the planet.
- How might relying on Earth observations not be a good model for scientists to use when studying other planets? Other planets may have characteristics that are not the same as on Earth. Titan, the large moon of Saturn, has features that look like river channels, but these were carved by liquid methane — not water!
National Science Education Standards
Grade K-4
Science as Inquiry - Content Standard A
Understanding About Scientific Inquiry
- Scientific investigations involve asking and answering a question and comparing the answer with what scientists already know about the world.
- Scientists use different kinds of investigations depending on the questions they are trying to answer. Types of investigations include describing objects, events, and organisms; classifying them; and doing a fair text (experimenting).
- Scientists develop explanations using observations (evidence) and what they already know about the world (scientific knowledge). Good explanations are based on evidence from investigations.
Earth and Space Science - Content Standard D
Changes in the Earth and Sky
- The surface of the Earth changes. Some changes are due to slow processes, such as erosion and weathering, and some changes are due to rapid processes, such as landslides, volcanic eruptions, and earthquakes - and impacts!
Science and Technology - Content Standard E
Understandings About Science and Technology
- People have always had questions about their world. Science is one way of answering questions and explaining the natural world.
- Scientists and engineers often work in teams with different individuals doing different things that contribute to the results. This understanding focuses primarily on teams working together and secondarily on the combination of scientist and engineer teams.
History and Nature of Science - Content Standard G
Science as a Human Endeavor
- Although men and women using scientific inquiry have learned much about objects, events, and phenomena in nature, much more remains to be understood. Science will never be finished.
Grades 5-8
Science as Inquiry - Content Standard A
Abilities Necessary to Do Scientific Inquiry
- Different kinds of questions suggest different kinds of scientific investigations. Some investigations involve observing and describing objects, organisms, or events; some involve collecting specimens; some involve experiments; some involve seeking more information; some involve discovery of new objects and phenomena; and some involve making models.
- Scientific explanations emphasize evidence, have logically consistent arguements, and use scientific principals, models, and theories. The scientific community accepts and uses such explainations until displaced by better scientific ones. When such displacement occurs, science advances.
- Science advances through legitimate skepticism. Asking questions and querying other scientists' explanations is part of scientific inquiry. Scientists evaluate the explanations proposed by other scientists by examining evidence, comparing evidence, identifying faulty reasoning, pointing out statements that go beyond the evidence, and suggesting alternative explanations for the same observations.
Earth and Space Science - Content Standard D
Structure of the Earth System
- Land forms are the result of a combination of constructive and destructive forces. Constructive forces include crustal deformation, volcanic eruption, and deposition of sediment, while destructive forces include weathering and erosion.
Earth's History
- The earth processes we see today, including erosion, movement of lithospheric plates, and changes in atmospheric composition, are similar to those that occurred in the past. Earth history is alos influenced by occasional catastrophes, such as the impact of an asteroid or comet.
History and Nature of Science - Content Standard G
Nature of Science
Science as a Human Endeavor
- Scientists formulate and test their explanations of nature using observation, experiments, and theoretical and mathematical models. Although all scientific ideas are tentative and subject to change and improvement in principle, for most major ideas in science, there is much experimental and observational confirmation. Those ideas are not likely to change greatly in the future. Scientists do and have changed their ideas about nature when they encounter new experimental evidence that does not match their existing explanations.
- It is part of scientific inquiry to evaluate the results of scientific investigations, experiments, observations, theoretical models, and the explanation proposed by other scientists. Evaluation includes reviewing the experimental procedures, examining the evidence, identifying faulty reasoning, pointing out statements that go beyond the evidence, and suggesting alternative explanations for the same observations. Although scientists may disagree about explanations of phenomena, about interpretations of data, or about the value of rival theories, they do agree that questioning, response to cirticism, and open communication are integral to the process of science. As scientific knowledge evolves, major disagreements are eventually resolved through such interactions between scientists.
