Download Lab 2 Crater Counting

Impact Crater Analysis
Objective
In this assignment we will compare the surface of the Moon to the surface of Mars and Earth. In doing so,
we will estimate the ages of two regions on Mars and compare and contrast those ages with Earth based
on assumptions about cratering rates
Background
It is difficult to understand the geologic history of Earth because plate tectonics and our atmosphere are
constantly changing the surface of the Earth. Fortunately, conditions on other planets and the Moon are
different and can help us understand the early history of our solar system.
When our solar system was being formed, conditions were very chaotic, violent and hazardous. Debris of
all sizes, shapes and compositions orbited the early Sun. Collisions happened frequently. These impacts
are well preserved on objects that don’t have an atmosphere or plate tectonics.
1. Where do we observe more craters: Earth or Moon? Why?
2. Which has a younger surface: Earth or Moon? How do we know?
3. What is the relationship between the number of craters and the age of the surface?
4. Take a look at the picture below (color version available on mrsvanvliet.weebly.com). These are
pictures of 4 of Jupiter’s moons. Rank the ages of the 4 surfaces from youngest to oldest. How did
you decide?
5. Research each of these 4 moons. Match the characteristics on the right side to the name on the left.
__________Io
A. Has the oldest surface in the solar system
__________Europa
B. Geologically active with many volcanoes
__________Ganymede
C. Has a water-ice crust
__________Callisto
D. Has a magnetic field and dark/light surface regions
6. Explain how each of the following processes can resurface a planet.
A. Volcanism
B. Erosion
7. This is a close up picture of the Moon’s surface. What region shows evidence of resurfacing? How
do you know?
8. Look at the image of Mars below. There are very few craters in this image. What do you think is
responsible for this?
On each of the attached images, there are 5 white bars. These bars represent: 8km, 16km, 32km, 64km
and 128km lengths.
9. Using those bars to help you estimate size, fill in the “number of craters in image” column in the
table below
Crater Size Range
(km)
Martian Crater Density Data Table
Northern Hemisphere
Southern Hemisphere
Number of craters
Number of craters
Number of craters
Number of craters
in image
in 1,000,000km2
in image
in 1,000,000km2
<8
8-16
16-32
32-64
64-128
10. To calculate the number of craters in 1,000,000km2, use the following calculation:
Number of craters per 1,000,000 km2 = Number of craters × (1,000,000 km2 / (Image size) km2)
The number and size of craters on a surface can give us an idea of how old a surface is. Using the
graph on the next page, we will figure out an approximate age for the surface of Mars.
11. Plot your data points from the table onto the Crater Density Graph. Put your points on the graph in
the middle of your size range. For example, if you had 200 craters in the 0-8 km size range, you
should put your point at the intersection of 200 on the y-axis, and 4 on the x-axis. (Note: the y-axis
of this graph has a logarithmic scale. Use a different color for the northern and southern
hemisphere data.
12. Determine the age of your surface. Once you have your points plotted, draw a best-fit straight line
through the points, as best you can. Your line should be parallel to the age lines on the graph. The
line you have drawn represents the average age of the cratered surface you have been examining.
Martian Northern Hemisphere Surface Age = __________ billion years old
Martian Southern Hemisphere Surface Age = __________ billion years old
13. Consider these two facts: (a) The Earth has been hit by as many impactors as the Moon and Mars.
(b) The province of BC has a total land area of about 945,000 km2. Use the graph to figure out how
many 12-km-sized craters have been formed in BC over the last 4 billion years.
14. Currently BC has zero 12 km impact craters. Come up with 2 or 3 good explanations for this.