Craters Around the Solar System

Summary
Students learn about the ages of solar system objects by examining craters on their surfaces.
Background and Theory
We have talked in sections about using crater density to determine the age of a surface. Here, you can examine photos of

Mars - Optical Images

Mercury - Optical images

Moon - Various Images

One Section of the Moon through the different cameras on the Clementine mission.
Froelich and Lovelace
Two more views of lumar impact craters: Impact Crater seen by Apollo 8 and Impact Crater seen by Apollo 13

Venus - Various Images

Radar Image 1
Here are two close-ups of craters on Venus: the Adivar Crater and the Golubnew Crater
Click here for more images of Venus.

Note that these images are taken using different techniques which means that they have different interpretations.

The Martian images were taken with a "normal" camera using the visible portion of the electromagnetic spectrum; thus the colors are close to the real colors which means that what you are seeing is different materials on the surface or shadows.
The colors in the Venusian images are false color representations showing the intensity of the returned radio waves. Since the wavelength used was close to 1 meter, surfaces with rocks or crevices that were about a meter in size are brighter in the radar image. That means that the bright spots on the image are *rougher*! Smoother surfaces will look darker, because they will reflect less light.
The images from Clementine are also close to natural color when taken through the UV/Visible camera. The others are simply intensity plots at one particular wavelength (e.g. the Near-IR camera worked at a wavelength of 1.1 microns)

A number of missions have gone to different places in the solar system. Some examples are the Mariner missions (4, 6, 7, and 9 went successfully to Mars; 2 and 5 went successfully to Venus; and 10 went to Mercury), the Viking missions to Mars, the Clementine mission to the moon, and the Magellan mission to Venus. There is a small collection of information about the various satellite missions as well.

Procedure
Look at the pictures and consider the crater density, the shape and size of the craters, and more importantly the number of craters of each size. Use this information to answer the following questions.

Based on the crater density in all of the images shown above, try to estimate the relative ages of the objects. Explain how you came to these conclusions.
How does the distribution of crater sizes (the number of craters of a given size) vary from surface to surface? Can you think of some possible reasons for this?
Based on these images, how do the craters on each of the planets differ from one another? What can these differences tell you about Mercury, Venus, Mars, and the Moon?
Consider the two close-up images of craters on Venus with the images of craters on the Moon. Notice how large the ejecta blanket is to the size of the crater. How is this different on Venus as compared to the Moon? Why do you think this is?

For more information on these planets, visit NASA Space Science Data Center.