The goal of this module is to investigate the heat absorption and transfer properties of various soils. The experiments will be done with Earth soils. Students will use their data and data from the Mars Viking Lander 1 to propose hypotheses and try to make an inference about Martian soil. This will further their understanding of the possibility of living on Mars and provide them the opportunity to suggest experiments for future missions to gather more information.

Students will compare their data with data from Mars Viking Lander 1. The comparison is limited because of the structure and function of the temperature sensor. Footpad 2 has a temperature sensor designed for the parachute entry phase. It survived landing and was buried under the soil. Consequently, it collected soil temperature data, but under different conditions than you will do with these experiments. Inferring a soil type based on the data and experiments is therefore unrealistic, however these and other soil experiments will help students understand soil properties and set them up to consider other experiments.

This module is composed of an opening page that asks about the possibility of living on Mars, an experiment where students collect data on various soils being warmed by a light source, an experiment where students collect data on various soils being warmed by the Sun, and plots of soil temperature data from a Viking Lander mission.

The Scientific Method is an underlying concept to this and all Live from Earth and Mars (LEM) modules. Students will develop a hypothesis, collect data, generate line graphs, and formulate a conclusion. Extensions and questions will conclude the module.

Engage students in the first part of the module for about twenty minutes. Use your experience from regular classroom activities to determine interest, pace, etc. The objective of the introduction is for students to develop interest and justification for doing the experiments and analysis. Students should understand a few basic concepts before entering the unit: interplanetary travel is not like in the media (it takes lots of time and resources), Mars and Earth have important similarities and differences, experiments always have a factor of uncertainty, and science is a method of collecting and analyzing information. Consider these options for introducing the module:

• Students using an Internet connection--Have students begin with the LEM homepage. Direct them to the "soils" module and make sure they write a response to the question. They should make two lists before proceeding. The next page helps summarize and prepare them for exploring the question. Allow a little free movement within the module for them to see both experiments, the data from Mars, and the questions. They should be at a good point for discussing the experiments and performing them.
• Demonstration with an Internet connection--This method will be nearly identical to the method above only with one computer controlled by you. Direct their activities and discussions by eliciting some oral and some written responses to your questions.
• Demonstration using overhead slides--select the "Print" from command from your Web Browser's menu for each page of this module. Use a color printer for those pages that have color (the lab can be printed in black with no loss of clarity). Note that many of the module pages will take more than one overhead slide to reproduce. Present the module as you would if you had an active Internet connection.
  

Students will record the temperature of a variety of "soil" types while they are being warmed by a light source. The experiment can be set up in several different ways. Here are a few suggestions for setting up the experiment:

1. Whole class demonstration
   The teacher as the primary experimenter with this variation. Students may be involved in the process with the teacher's supervision during the demonstration. The rest of the students are involved only to the extent of watching and recording data. This allows good control of variables, fewer materials, and less time required for set-up.
2. Centers
   Students are the primary experimenters with this variation. The teacher becomes the facilitator of the process while monitoring the center as the experiment proceeds. This experiment would be one of several centers to be running at the same time. This allows the students to have personal involvement in the experiment. It also allows for fewer materials and less set-up than if the whole class does the experiment at the same time.
3. Cooperative Groups
   Students are the primary experimenters with this variation. The teacher becomes the facilitator of the process while monitoring the groups as the experiment proceeds. Each group would be running the same experiment simultaneously. This allows the students to have personal involvement in the experiment. This variation requires materials and set-up for each group.

Note: The student labs (or any page, for that matter) can be printed by selecting the "Print" command from your Web Browser's menu.

Begin by reading the Student Lab Sheets. They contain step-by-step instructions for each experiment. Students will enter the experiment after an initial experience asking about the possibility of living on Mars (the opening pages of this module) then record the temperatures of soils as they are warmed by a light source. One lab uses table lamps and the other uses Sunlight. Students will answer questions about the lab and attempt to connect their data to a data plot from Mars soil temperatures. The Outside Lab most closely emulates the Martian data while the Inside Lab as given will not resemble a solar heating cycle.

The teacher will need to provide the following materials:

• soil samples*
• shallow Styrofoam cups (one per soil sample x number of "groups")
• plastic wrap (enough to cover each cup)
• rubber bands (one for each cup)
• thermometer (one for each cup)
• heat source (100 W light bulbs in reflectors work fine, one for each "group")
• data sheet (one for each "group")
• pencil (one for each "group")
• timer (room clock, digital alarm, etc.)

*There should be enough soil to completely fill the Styrofoam cups. The recommended soils to test are the following:

• clay soil
• fill dirt
• potting soil
• sand
• top soil

Controlled variables must be monitored closely during set up of the experiment. Prepare each sample as consistently as possible to ensure the controlled variables will remain constant! You will try to keep the volume, mass, moisture content, distance from light source, and depth of thermometer the same for all samples.

When cups are filled, soil should be packed to near the top of the cup to avoid air spaces within the soil. A small airspace should be left at the top of the cup. Insert a thermometer into the side of the cup (note the depth), cover each cup with plastic wrap, and seal it with the rubber band.

Classroom Discussion/Questions:
Before the experiment takes place, there should be a class discussion about the experiment and about scientific methodology.

Possible questions to discuss:

• What are we trying to find out?
• Why are we trying to find this out?
• How will we do it?
• Why has the experiment been set up this way (showing set-up)?
• What has to stay the same (controlled variables)?
• What might happen if our controlled variables aren't kept constant?
• What will change (time and temperature of the soil)?
• Which are the independent and dependent variables?
• How will we measure the results?
• What does it mean if our hypothesis is wrong?
• What could the results tell us?
• Why are our conclusions always based on our results?

During the Experiment:
Students should get a chance to make observations of the soil before trying to generate their hypotheses.

Students will be completing their student worksheets and completing the data sheet as they do the experiment.

The graph is generated from students' results. Because this experiment has data taken over time, this will be a line graph. Use a different colored line for each soil sample. Each student will need to have some background on how to generate a line graph from data, or the graph could be generated as a class. Have students either plot the Mars soil data or show the included plot. Try to get them to suggest which of their soils most closely matches the plot of Martian soil temperatures. It is important students understand their data and analysis has limitations (heating by lamp rather than sun, atmospheric influences, moisture content, etc.). This may provide more creativity for for suggesting experiments for future lander missions to gather the information they need to provide a deeper analysis.

Questions for after the experiment:

• What are some experiments we should do on Earth and Mars to determine Martian soil type?
• How useful were these experiments in determining Martian soil type?
• What is needed in "soil" to support plant growth?
• Which kind of soil does Mars most likely have?
• What is the likelihood we could grow food in Martian soil?
• How would your results be affected if you forgot to control a variable?

Extensions

• Collect data for the cooling of soils (the reverse of the experiment in this module).
• Does moisture in soil affect the heating rate?
• Does the composition of the soil affect the heating rate?
• Does the density of the soil affect the heating rate?
• Does using different cups affect the heating rate of soils?
• Explore the literature and media related to Mars. These include mythology, science fiction, movies, and astronomical resources. Discuss how these have shaped our conceptions and misconception of Mars, space, and colonization.
• How is the heating rate of soils effected by depth?
• How is the heating rate of soils effected by geographic location? Which makes more difference: longitude, latitude, or altitude?
• Look for other connections between Mars and Earth. Data exists for air pressure, air temperature, and humidity.
• Plot data over an extended length of time and look for cycles. Similar data is available from Mars.
• Try alternate forms of data gathering and analysis. Use a graphing calculator or computer to record the temperature information. Recommended devices are the "Calculator Based Laboratory" (CBL) from Texas Instruments and computer interface devices from Vernier Incorporated.
• Would we get the same results if the soil samples are farther from the heat source? Why or why not?
• Write a story or essay describing a Martian colony focusing on the resources Mars offers. Include a discussion of the types of jobs people will have, the rules under which the colony would operate, the responsibilities people would have as citizens of a colony, and the "impact" each individual would make on the planet.

A list of the AAAS Benchmarks addressed in this module are available.

Other Mars resources are available on the Mars Profile page and the Resources index. Information on Viking Lander Soils and Surface Materials will soon be available.

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