ESCI 110: Planetary Surfaces
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Exercise 3
Surfaces of the Planets and Moons
Introduction
Our knowledge of the solar system has exploded with the space exploration programs of
the last 40 years. This new knowledge has led to two major conclusions: 1) impacts of objects
crashing into planetary and lunar surfaces was very important in modifying these surfaces,
especially early in the history of the solar system, and 2) the earth is unique within the solar
system compared to the other planets and moons.
In this exercise we will look at planetary surfaces and introduce the general categories of
materials they are made of and the processes that modify them.
Objectives
Upon completion of this exercise, you should be able to:
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List the types of materials that make up planetary surfaces
Provide examples of planets or moons with surfaces dominated by gasses, ice, rocks or
liquid water
List the basic types of processes that modify planetary surfaces
Identify the effects of different processes in modifying planetary surfaces
Determine the relative age of different surfaces on the same moon or planet
Background Information
In a very general way, the composition of the surfaces of the moons and planets can be
divided into four major categories:

Gas giants. The Jovian planets apparently have no solid surface as we would be familiar
with it. Instead, they are composed of giant balls of gas, with the gasses becoming denser
with depth until they gradually turn into liquid. The outer surfaces of these planets are
therefore in constant motion.

Ice surfaces. These surfaces are dominated by frozen liquids that have relatively low
melting points. Any process that generates enough heat will therefore melt the surface,
smoothing it out.
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Rocky surfaces. These surfaces are dominated by solid materials that have relatively
high melting points, and are capable of maintaining substantial relief over time.
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Liquid surfaces. Significant portions of the planet are covered with liquid.
ESCI 110: Planetary Surfaces
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The processes which modify planetary surfaces can be divided into the following
categories:
 Impacts. Objects that strike the surface of a moon or planet are typically traveling at
tens of thousands of kilometers an hour relative to the target. On a solid surface the
collision will leave an impact crater. A relatively fresh impact crater may send rays
of ejecta across the land, and large craters will generally have a raised area in the
center caused by the rebound of rocks compressed directly under the impact site.
 Volcanoes. Volcanoes are mountainous landforms that build up where liquid rock
material escapes from the surface of the planet or moon. In many cases lava flows
may be found extending from the central vent of the volcano.
 Tectonics. Forces within the moon or planet may put stress on the surface, and
modify it in the form of faults or folds.
 Surface processes. If the moon or planet has an ocean or atmosphere, the surface may
be significantly modified by the influence of wind, running water, ice, waves or
gravity.
One very important consideration in studying the history of a planetary surface is to
determine the age of the surface under study. Impacts occurred at the greatest rate early in the
history of the solar system, and impact craters also accumulate over time. Therefore older
surfaces will have a higher density of impact craters than younger surfaces.
We can also use the principle of crosscutting relationships to determine the relative age
of adjacent surfaces. If a fault cuts through an impact crater, for example, we know that the
crater had to be there before the fault began to move.
Questions (If any of the images are unclear ask your instructor to display them up on the screen
so you may observe a clear photograph)
1. The image to the right shows part of the
surface of the moon. The lighter area on the left is
part of the lunar highlands, while the dark region on
the right is part of one of the maria. Which process
from the list above dominates the surface of the
highlands?
__________________________
Which surface is older, the highlands or the
maria, and how can you tell from this photo?
__________________________________________
__________________________________________
__________________________________________
ESCI 110: Planetary Surfaces
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2. The image to the right
shows part of the surface of
Mercury. Is this surface gaseous,
icy, rocky or liquid?
___________________
From what you see in the
image, is the surface of Mercury
closer in age to the highlands of the
Moon or the lunar maria? Explain
the reason for your answer.
____________________________
____________________________
______________________________________________________________________________
3. This image shows part of the surface of
Jupiter. What type of material is Jupiter made of, and
what is your evidence?
_____________________________________________
Jupiter was recently struck by several pieces of a
large comet. Circle the evidence of impact you see on
this image, and describe what has happened to these
impact structures since they formed:
____________________________________________________________________________
_____________________________________________________________________________
4. The image to the right is a radar image that
shows the solid surface of part of Venus beneath the
clouds. The surface of Venus is clearly composed of
rocky material and volcanoes that are at least somewhat
similar to that found on parts of the earth. What process
is responsible for this part of the landscape on Venus?
_____________________________________________
How old is the surface of this part of Venus
compared to the surface of the Moon?
__________________________________________
ESCI 110: Planetary Surfaces
Jupiter’s moon Io
Close up of Surface of Ganymede
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Surface of Ganymede
Surface of Europa
5. These four images show surfaces of three of the moons of Jupiter. What type of
material is the surface of Europa composed of? _______________________________________
What process dominates the surface of Io? ___________________________________________
What evidence do you see for tectonic activity on Ganymede? ___________________________
Which part of which moon appears to be the oldest in age, and what evidence supports that
conclusion from the images provided? _____________________________________________
____________________________________________________________________________
ESCI 110: Planetary Surfaces
Olympus Mons
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Dune Field
Ophir Chasma
6. The three images above show different parts of the surface of Mars at three
completely different scales (Olympus Mons is the size of Ohio, Ophir Chasma is as deep as the
Grand Canyon, and the dune field is show at a high magnification).
Overall, is the surface of Mars relatively young or very old? ____________
Which two processes dominated the surfaces in these regions? ____________________
7. Earth. This photo has
been converted to a grayscale
image from a color photo taken
by the Apollo 17 astronauts.
Saudi Arabia is in the middle of
the picture.
What two types of
materials dominate the visible
surface of the earth?
________________________________
What evidence do you see for tectonic activity in this image? ______________________
Is the surface of the earth relatively young or relatively old compared to other planetary
surfaces, and how can you tell?
_____________________________________________________