Live From Mars Teacher's Guide Preview: Activity 1.2

From: (Jan Wee)
Subject: Live From Mars Teacher's Guide Preview: Activity 1.2
Date: Fri, 04 Oct 1996 15:26:50 -0500

Dear discuss-lfm members,

For your preview, Activity 1.2. 

Jan Wee

ACTIVITY 1.2: Mapping the Topography of Unknown Surfaces

Teacher Background
Mapping Mars with Global Surveyor
The Viking orbiters provided wonderful pictures and subsequent image 
processing created mosaics of most of Mars. But much important 
information is still missing. An example is something as basic as the 
elevation of future landing sites. Because Mars' atmosphere is so thin, 
parachutes are relatively less effective than here on Earth. (There's less 
resistance to slow the spacecraft down: Newton's Laws, once more!) So, 
it's critical to know how thick a layer of Martian atmosphere you're 
traveling through before you reach the surface. If the landing sites 
are too high up, there'll be too little atmosphere, and you may design 
a braking system that won't work well enough to slow your descent! 
Ouch... back to the drawing board. Current uncertainties about 
Martian elevations are as large as 3 kilometers, enough to make 
spacecraft designers very nervous. Enter MOLA.
One of the six instruments on board Mars Global Surveyor will be the Mars 
Orbiter Laser Altimeter (MOLA). MOLA's laser will fire pulses of infrared 
light 10 times each second. By measuring the length of time it takes for 
the light to return to the spacecraft, scientists can determine the 
distance to the planet's surface. (Spacecraft navigation data gives the 
distance of MGS from the center of the planet, so putting the two data 
sets together will yield Martian surface elevation with a precision of a 
few tens of meters.) MOLA will provide information to construct the first 
detailed topographic map of Mars, showing fine details of plains, valleys, 
craters and mountains.

Note: Since topographic maps use sea level to define zero elevation, we 
Earthlings measure the height or depth of all landforms relative to sea 
level. Of course there's no sea on Mars, so scientists describe elevations 
relative to a zero level called the "datum" surface.

Students will be able to describe in words and graphic displays the 
elevation or depression profile of sections of Mars' Olympus Mons and/or 
Valles Marineris.
Students will demonstrate the ability to describe the operation of 
the MGS laser altimeter.
Students will be able to explain how orbiting spacecraft build up 
global maps one data slice at a time.
Students will use contour maps to create 3-dimensional Martian 
Students will simulate the operation of MOLA.
Students will transform 2-D numerical measurements into 3-D 
representations of hidden landforms.

Materials: (for each team of 3/4 students)
1 shoebox with lid
17 sheets of cm grid paper (16 cm x 30 cm)
adhesive/scotch tape 
metric ruler
contour map of Olympus Mons and Valles Marineris (provided with this 
Guide: duplicate and scale up to give the best "fit" with a standard 
shoebox); you may wish to duplicate this and cut into "jigsaw puzzle" 
pieces, covering up place names, in order to increase the challenge aspect 
of this Activity.
1 grid support constructed by gluing one complete 16 cm x 30 cm grid 
paper onto a piece of cardboard
Altimeter rod (10 cm length, cut from a coat hanger or wooden skewer)
an awl, leather punch or other sharp object to punch holes in top of 
shoebox papier mache, plaster of paris, or small pieces of rocks, 
wood, aluminum foil that can be used to make a Martian terrain 
inside bottom of shoebox

datum surface
topographic map

Explain why NASA needs elevation data from Mars, and how MOLA operates, 
or have teams go online and research MOLA and report back. As noted 
above, the altitude of a landing site can be crucial for spacecraft safety. 

Tell students that they represent a NASA Mission team specializing in 
mapping the elevation of a little known planet. This Activity simulates 
the process of gathering data about a surface which can't be measured 
directly. Working in teams, students will first construct a segment of 
Mars -- in 3 dimensions -- from current contour maps, without revealing 
its exact topography to other teams. This Challenge landscape will be 
hidden inside a securely-closed shoebox. Each team, in turn, will receive a 
Challenge landscape created by another team, and unknown to them. Their 
mission is to collect simulated altimeter data on the Challenge landscape, 
and create a 3-D paper profile map of what they think is hidden in the box 
(the "Result" landscape). At the end of the Activity, they'll see how 
accurately Challenge and Result landscapes match.

Note: Ideally, this is a two stage Activity: you can do just the measuring 
activity, but the students will benefit both from creating the Challenge 
and Result landscapes (scaling, plotting, cooperation and model-making 
skills) which will let them literally get their hands on two sections of 

Making the Challenge landscape
1. Working from the sections of contour maps you provide, each team 
should make a three-dimensional Mars landscape covering the bottom of 
the shoebox. 
2. Tape or glue a piece of cm grid paper to box lid. Label horizontal and 
vertical axis 0, 1, 2, 3, etc. 
3. Using a sharpened awl or leather punch, punch small holes at 
intersections of the grid.
4. Seal box with tape. Exchange the closed Martian Challenge boxes.

Altimeter Simulation:
Tell students that they will now simulate the Mars Orbital Laser 
Altimeter using the "Altimeter rod" and collect data representing the Mars 
terrain hidden in the shoebox. 

The teacher might want to demonstrate the following procedure:
1. Find the coordinates (0,0) on the box top.
2. Insert the Altimeter rod into the hole at (0,0), until it comes in 
contact with the landform inside.
3. Keeping the rod upright, measure how much is showing above the lid. 
Subtract this from its full 10 cm. length to find the distance from "orbit" 
(lid) to surface (or use a piece of easily removable paper tape as a marker, 
and remove and measure the rod.)
4. On the graph paper plotting grid, locate the (0,0) coordinate and 
count down the number of centimeters which the rod measured. Plot this 
point on the grid.
5. Repeat this procedure across the row (0,1), (0,2) (0,3), (0,4), etc. to 
6. Connect the altimeter readings across the row.
7. Cut along this data line.
8. Fold along the dotted line (row 16) and glue on the appropriate row 
(0,0 for the example above) of the grid support. You now have the first 
row of your three dimensional Mars landscape. (See Diagram)


Note: to move things along, in a team of 3-4 students, one might be MOLA 
and collect and measure altitude, one might plot the data points, and 
another might cut out and assemble the profile sheet once each row of 
data has been collected. Students should rotate through tasks to expose 
each of them to all parts of the process.

Repeat this procedure for:
the second row (coordinates (1,0), (1,1), (1,2), (1,3), (1,4), etc. to
the third row (coordinates (2,0), (2,1), (2,2), (2,3), (2,4), etc. to (2,30);

and so on, up to the sixteenth row (coordinates (16,0), (16,1), (16,2), 
(16,3), (16,4), etc. to (16,30).

After class has complete the hands-on procedure:
1. Look at the Challenge and Result profiles. Ask students to determine 
which Result corresponds to which Challenge.
2. If you have had students create sections of Valles Marineris and 
Olympus Mons as the Challenge landscapes, assemble them and enjoy the 
3. Suggested discussion questions:
How could a more detailed map of the surface be made? (more holes, holes 
closer together, thinner probes)
Where else could this map-making technique be used? (other planets and 
their moons, ocean floors, remote areas that are difficult to reach 
What other techniques beside lasers could be used? (e.g. radar -- as on 
NASA's Magellan spacecraft which surveyed Venus, or the Space Shuttles 
SIR-C, or sonar, as in submarines.)
In what ways will future Mars Missions use MOLA information?
4.  Locate a topographical map of your area: what is the scale? What 
symbols are used? 
5. Invite a Surveyor (perhaps a student's parent?) to class:. What tools 
do they use? Do they ever work with GPS (Global Positioning Satellite) 
which now provides altitude data, as well as latitude and longitude.
6. Record in Mission Logbooks successes or problems in completing this 

MOLA's laser will fire infrared pulses every ten seconds. These pulses of 
energy travel at the speed of light (186,000 miles per second). NASA 
scientists can determine the distance from the spacecraft to the land 
form below by timing how long it takes the pulse to travel from the 
spacecraft to the surface and back to the spacecraft (which you can think 
of as a kind of echo). Distance = Speed x Time (e.g., travel at 50 miles per
hour for 3 hours and you have gone a distance of 150 miles.) If 
we divide this distance by 2, we have the distance from the spacecraft 
to the ground. 

Teachers of older students might have them calibrate their measuring 
rods in seconds instead of length. Then, remind students of the velocity of 
light and have them calculate the distances to the various points in their 
topographical models. As a starter, MGS's orbit is X kilometers (go online 
and find out...) above Mars. Given that the standard shoe box is X 
centimeters high (measure one), and that the base of the box can be 
considered Mars' datum (see above) then each cm on the Altimeter 
represents X seconds (here's the math challenge!)

Language Arts:
Research how laser altimeters operate and report to class. Construct a 
visual (poster, 3-D mock-up, etc.) to use in your report.

Research on the use of sonar in other technologies and in the animal 
kingdom (dolphins, whales, bats).

Adapting this Activity to Higher or Lower Grades
Younger students may find this Activity still works well with arbitrary 
landforms, other than those modeled on actual Martian topography. In this 
case, simply have each team create an interesting mountain/valley shape, 
which then becomes the target for other teams to survey and represent. 

For a sturdy model which you'll be able to use multiple times, create the 
surface by crumpling newspaper and covering it with aluminum foil. Pour 
plaster of paris or apply papier mache over the foil, and spread the plaster 
all the way to the box sides to anchor the surface. It's best to have 1-3 
"mountains" or one complex feature in each box; try to make the highest 
and lowest points about 10 cm different in length. 

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