Planet Trek:

Mapping New Worlds

Part III: Concept Application: Mapping

Activity # 6 - Discovering and Mapping New Worlds

For this activity you will be making a simulated planetary surface using a potato and identifying various surface features. To complete this activity you will need:

First, you will need to identify the north and south poles of your potato world. On a real world this is determined by the axis of rotation. Generally, worlds will rotate with the axis going through the shortest position. However, to make this task easier, it might be better if your potato rotates with the longest possible axis. A short axis is possible, and could be used by those who want more of a challenge! (Note: You could use a meat skewer to represent the axis pushed through your potato, however once the potato is pierced, it will likely deteriorate more quickly.)

You might remember that the equator, lines of latitude and longitude are all determined by projecting positions on the world's axis out through the surface. However, for your potato world, you will have to vary from this method and determine the equator and other lines of latitude and longitude by equally spacing them according to surface measurements.

Next, determine the location of the equator at an equal distance between the poles. Draw a line for your equator in one color, the remainder of your lines of latitude will be in a second color. You will need to take measurements at several locations around the potato to make sure your equator is always at the correct distance. Draw lines of latitude at 15 degree intervals both north and south of the equator, terminating at the pole which is a point (rather than a line) at 90 degrees. Lines of latitude are also referred to as "parallels" because they are always equal distance apart.

Next, determine a "prime meridian" and draw a line perpendicular to the equator that intersects both poles in the same color you used for your equator. The 180th meridian should lie on the reverse side of your potato world at exactly half the distance around the potato at all points from your "prime meridian." This line, and all other lines of longitude will be drawn using the second color of ink.You will also draw these lines at 15 degree intervals. Drawing the lines of longitude (meridians) on your potato world will be more difficult, because at any latitude they must be equal distance apart.

Because your Potato World is irregular, not spherical, you will need to take measurements at numerous locations around your world.


  1. Locate the north & south pole - this should be at the center of rotation for the axis of your world.
  2. Locate the equator by taking several measurements equal distance between the poles, marking each position and drawing a line to connect the marks.
  3. Construct a prime meridian by drawing a line from the north to south pole that intersects the equator at a right angle. The equator and prime meridian should be drawn in a different color than the other lines of latitude & longitude!
  4. To construct the lines of latitude in the northern hemisphere at 15 degree intervals, measure the distance between the pole and equator at a specific position. USE METRIC MEASUREMENTS ONLY! You will probably need to make all measurements using millimeters, as it will be easiest to divide (to the nearest compatible number) when using these smaller units. Divide this distance by 6 (6X15=90). Make FIVE marks at that measured interval to determine where you lines of latitude will fall. Remember the 6th mark is already made - at the north pole. Repeat the measurement and marking process at several positions around the potato, then connect the marks to form your lines of latitude.
  5. Repeat the process for the southern hemisphere.
  6. Construct your 180th meridian by finding the point exactly half way around your potato from the prime meridian.
  7. Constructing your lines of longitude is a bit more difficult because of the shape of the potato. You will be working with making your lines of longitude much closer together than your lines of latitude. First, construct these in the western hemisphere. Measure the distance between the prime meridian and 180th meridian. Divide this distance by twelve (12X15=180). Make eleven marks at equal intervals to mark equal distances between meridians. Repeat the measurement process at several positions along the length of the potato, then connect the marks to form the lines of longitude.
  8. Repeat the process for the eastern hemisphere.

Now, you will give your world a name and choose a theme for naming surface features. You will need to identify 12 surface features, based on the irregularities in your potato. For example, eyes could be craters and bumps could be mountains or volcanoes. Complete the WORKSHEET that includes the following information:

When identifying surface features, keep in mind that you will be using descriptions of what your potato's irregularities LOOK like, not the process by which they are formed. Use your imagination to find as many different kinds of features as possible!

Finally, you need to map the surface of your potato world using the 360 DEGREE MAP.

Once you have made your maps, named your features and "interpreted" your worlds, swap maps with another student and compare each others worlds. Does one world have more craters or volcanoes than another? Do any have huge rifts that others lack? What features are in common? Finally, after determining the answers to these questions and comparing your maps, actually look at your potato planets and compare your worlds.

After completing your potato and map, you may want to write a tourist brochure for your world! Tell about all the interesting places to visit on your world's surface.

Unfortunately, potato worlds have a limited life span before they begin to deteriorate. So be sure to take lots of pictures to keep with your map!

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