Planetary Surfaces

Teacher's Notes

Exploring the Martian surface for water, minerals, and suitable building materials. Transparency Master

This unit is an introduction to erosion and planetary surfaces as they relate to the Earth, Mars, and the Moon. Erosion is a generic term which describes a process by which a surface is gradually modified ( eroded) by external agents acting on the surface. In this case we are dealing with various types of planetary erosion. A simple surface is created and then it is exposed to various erosion-producing agents. The principle agents of erosion are water and ice, wind, and in the case of the moon, abrasion from micro-meteorites from space.

Things to Emphasize

1. Like the early pioneers of the New World, the first humans to reach Mars will have to make extensive use of the raw materials provided by the environment in which they find themselves.
2. Erosion is the process by which a geological feature is degraded and ultimately destroyed and in doing so new geological features are created.
3. A geological feature may be as small as a sand castle on a beach or as large as a range of mountains.
4. Erosion can occur on a wide range of time scales. Noticeable erosion may take only a few minutes or it may take hundreds of millions of years.
5. Erosion is caused by the action of one or more of the following agents:
   1. wind,
   2. running water ( such as rivers) or moving ice (such as flowing glaciers),
   3. large fluctuations of temperature which may include cycles of the freezing and thawing of water (called fatigue failure due to repetitious contraction and expansion).
   4. and the action of abrasive materials carried by ice, water or wind.
6. Science investigation involves a multi-step inquiry process: ask an initial question, plan the investigation, record observations and collect data, analyse data to draw a conclusion, and communicate the findings.

Build a Planetary Surface

Transparency Master

Instructions Obtain a quantity of clean dry sand and some rocks of assorted sizes. Add the sand to a large oven-sized aluminum foil roasting pan (the disposable type) to make the pan about one half full of sand. Make a small hole as shown to allow excess water to drain out of the pan. Dampen the sand slightly. Make a few crater shapes in the sand (this can be done by dropping various sized rocks onto the sandy surface), and add a few rocks to complete your simulated planetary surface. Make two more similar planetary surfaces (a total of three). Build a small wooden frame to cover each simulator. Set up each simulation as shown below.

Investigating Erosion

Transparency Master	Wind and Water In this simulation the "frame" provides no protection. Set up the simulator outdoors in an undisturbed location and leave it for about one month. The process of erosion can also be "simulated" by using a watering-can to simulate rain and a hand-held cardboard fan to simulate the effects of wind on the surface.
Transparency Master	Wind Only In this simulation the "frame" provides rain protection. Cover the top with clear plastic and fasten it securely so it will not break or blow away. Anchor the frame securely to the ground too. Set up the simulator outdoors in an undisturbed location and leave it for about one month.
Transparency Master	Neither Wind nor Water In this simulation the "frame" provides rain and wind protection. Cover the top and sides with clear plastic and fasten it securely so it will not break or blow away. Anchor the frame securely to the ground too. Set up the simulator outdoors in an undisturbed location and leave it for about one month.

Key ideas

In this investigation three types of erosion are compared: erosion of the Earth's surface, Mars' surface and the Moon's surface.

All three surfaces start out looking more or less identical. That is, they are heavily cratered and relatively flat. To some extent this resembles all three planets, the Earth, Mars, and the Moon (which for simplicity we will assume is a small planet) about 500 million years after their formation.

1. The Earth has experienced erosion from the effects of wind, water, ice, and rain for most of its 5 billion year history.

2. Mars, by contrast, has had practically no erosion induced by running water for about the last 1 billion years of its 5 billion year history. Today wind is probably the major agent of erosion on Mars.

3. The Moon, as far as we know, has never had significant erosion from either wind or water in its 5 billion year history. All erosion on the Moon is the result of billions of years of meteorite impacts which have gradually pulverized the surface.

Student Activities

1. Mapping a Planetary Surface, Student Activity Master #1
   
   
2. Mapping a Planetary Surface, Student Activity Master #1
   
   
3. Building a Planetary Erosion Simulator, Student Activity Master

Topics for class discussion

1. The Moon and the Earth have both been pummelled by meteorites during the past 5 billion years. One can easily see the craters on the Moon with a pair of binoculars. Why are craters so rare on the Earth? Do you know of any large craters on Earth?

2. Based on your observations in this experiment, and knowing Mars has neither rain nor rivers on the surface, but that it has a very thin atmosphere, would you expect:
   
   
   1. Mars to have more or fewer craters than the Moon? Explain your conclusion.

   2. Mars to have more or fewer craters than the Earth? Explain your conclusion.

   3. "Falling" stars (which are called meteors) are a result of a meteoroid burning up as it enters the earth's atmosphere at speeds of 20-100 kilometres per second! A fragment of a meteoroid which survives entry into the Earth's atmosphere is called a meteorite.

      Where would astronauts be safest from a possible meteoroid impact, Mars, Earth, or the Moon? Why?

3. How and where might astronauts create a habitat on Mars which would give them some protection from meteoroid impacts?