What do you think will happen if an asteroid or a comet hits Earth?
Evidence of impacts caused by asteroids and comets have been found in various places on Earth and scientists believe that in the distant past, an asteroid or a comet impact might have led to the extinction of dinosaurs.
In this activity, students will simulate the formation of a crater using some common materials like marbles, flour, and a basin. It is intended for Grade 8 students, particularly, for the topic ‘Other Members of the Solar System (Comets, Meteors, and Asteroids)’ in the Grade 8 Science Learner’s Material (Unit 2, Module 3) published by the Department of Education. They will learn what an impact crater looks like and how the size of an object affects the size of the crater formed. This activity effectively illustrates to students that other members of the solar system, particularly comets, meteors, and asteroids, are capable of causing catastrophic effects in the event of an impact with Earth.
Developing the Lesson
The discussion may start by establishing that impact craters (craters formed due to an impact of a space body like an asteroid or a comet) are formed naturally in the solar system and elsewhere in the universe. You may show a photo of the moon littered with craters, or perhaps a famous crater found on Earth.
Craters have also been found in other bodies in the solar system like in rocky planets, moons of other planets, and asteroids.
You may then ask the students: ‘What do you think will happen if an asteroid or a comet hits Earth?’ You may then show an illustration depicting the demise of the dinosaurs some 65 million years ago.
Student’s answers may vary, but it is important that you summarize their responses and lead to the conclusion that during such unfortunate occurrences, catastrophic and globally-devastating effects may be expected.
To effectively demonstrate a space rock or a comet hitting the Earth’s surface, you may then perform the following activity.
Create a Crater!
After performing this activity, you should be able to:
1. describe the appearance of a crater; and
2. explain how the size of an asteroid or comet affect the size of a crater.
3 marbles of various sizes
large plastic basin
1 kilo of flour
1. Put the flour in the basin and spread it evenly (Figure 6).
2. Place the basin on the floor. Drop a marble on the flour from a height of about 1 meter (Figure 7). Observe what happens as the marble hits the flour’s surface. Record your observations.
3. Repeat steps 1 and 2 for the other marbles.
How does the size of the marble affect the size of the “crater” formed?
Each time the marble is dropped (Step 2), ask the students the following question: ‘Compare the hole formed by an asteroid with that of the hole formed by the marble. Do you notice anything similar?’
The activity simulates the formation of an impact crater. Students should notice 2 things: (1) that there is a depression at the center and (2) it forms a raised outer rim. The 3 images below show a typical “crater” formed through this activity (Figure 10,11, and 12 show the same “crater”, photographed from different angles).
Students should also notice that the marble’s impact caused flour to be ejected from the crater in all directions. In this photo (Figure 13), the basin was removed for clarity.
Ask the students to recall or review their observations for all 3 marbles (for the small, medium, large) and then ask the question “How does the size of the marble affect the size of the ‘crater’ formed?”.
If the activity was performed and executed as planned, student should notice that the small marble formed a small “crater”, and the large marble formed a larger “crater”, and arrive at the conclusion that the larger the marble is, the larger the “crater” formed (or stated the other way, the smaller the marble is, the smaller the “crater” formed ).
You can then ask the students, “What happens when an asteroid or comet hits the surface a moon or a planet?”. You may then show a video animation simulating the formation of an impact crater (copyright DK Multimedia, from a Red Shift 3 video lesson) .
You may elicit reactions from the students. You can then summarize the key points discussed in the activity by going back to the objectives: (1) describe the appearance of a crater; and (2) explain how the size of an asteroid or comet affect the size of a crater. Before ending the lesson,engage the student with this question: ‘Can you think of other factors that may affect the size of an impact crater?’
Peer Reviewers: Mr. Eligio C. Obille, Jr. and Dr. Ma. Helen dH Catalan
Prepared by the National Institute for Science and Mathematics Education Development, University of the Philippines, Diliman