Download crater creator lab

Crater Creator
Background
The planets and moons have been continuously pelted by asteroids ever since their formation. Just look
at the Moon through a small telescope or a good pair of binoculars and you will see that its surface is
covered by craters.
If we assume that asteroids strike all regions of a planetary body at approximately the same rate (an
assumption may or may not be correct), every region should have the same number of craters – we call
this crater density. Regions with higher crater densities tend to be older than regions with lower crater
densities. For example, if you stand in the rain for a long time you will get soaked (like a planet or
moon that has been in space for a long time), but if you make a quick dash to shelter (like a newer
planet or moon) you will only get spattered with a few raindrops.
On the other hand, if the planet or moon is geologically active or has an atmosphere, then processes
such as weathering, erosion, tectonism and volcanism can partially or completely erase craters.
What other factors might influence crater density? Beginning when the planets formed about 4.5
billion years ago, the amount of debris began to decrease as collisions and impacts cleaned up the
debris. There may also be a relationship between the amount of craters and the distance from the
asteroid belt. Mars, for example, is located nearer to the asteroid belt than the Earth is, and may have a
rate of crater formation roughly twice that of Earth. We might also want to consider the sizes of the
planets – large planets such as Jupiter possess greater gravitational fields that attract more impacts.
Higher gravity also means that objects hit the surface with more speed.
Problem
How are craters formed?
Is the speed or diameter of an asteroid the most important variable in determining the size of a crater?
How do we interpret the surfaces of the Jovian (Jupiter’s) moons?
Materials
Tray of sand or flour
Small glass marble
Large glass marble
Meter stick
Metric ruler
Photographs of Jupiter’s moons
Procedure
1. Smooth the surface of the sand/flour in your tray.
2. Drop the small glass marble into the tray from 50 cm.
3. Measure the diameter of the craters and record in the data table. Repeat 2 more times.
4. Repeat steps 1 – 3 with the large glass marble.
5. Smooth the surface of the sand/flour in your tray.
6. Drop the small glass marble into the tray from 100 cm.
7. Measure the diameter of the craters and record in the data table. Repeat 2 more times.
(***Remember that on earth acceleration of an object due to gravity is a constant, so that the
objects speed will be larger the farther it falls***)
8. Repeat steps 5 – 7 with the large glass marble.
9. Use the images provided, count all identifiable craters. If you are not sure of a particular feature
is an impact crater, assume that it is not. Record in your data table.
10. Calculate the crater densities for each of Jupiter’s moons by dividing the number of craters by
the image area
Results
Trial
Small Marble
(50 cm)
Large Marble
(50 cm)
Small Marble
(100 cm)
Io
Ganymade
Callisto
Large Marble
(100 cm)
1
2
3
Average
Image Area
1,500,000 km
2,200 km
1,700 km
# of Craters
Crater Density
(crater / km)
Conclusion
1. How are craters formed?
2. Which variable – speed or size – was the most important for creating large craters?
3. Describe the surface of each of the moons in terms of crater density.
4. What can you say about the relative ages of the moons (read the background)?
5. List the moons in order from oldest to youngest.
Io
Ganymede
Callisto