How do planetary geologists study rocks on a planet that no human has ever visited and that is as much as 50 million miles away? NASA uses robotic rovers to do this type of study on the surface of Mars. To observe a pristine (or fresh) sample of rock, geologists on Earth would break the rock open with a rock hammer. Instead of breaking the rock open with a hammer, the Mars Exploration Rover (MER) will have a special tool called the Rock Abrasion Tool, or RAT, to remove outer layers of rock and expose underlying material for examination by the Microscopic Imager (which is like a geologist's hand lens) or Pancam (the rover camera).
An Edible Rat will help students understand the process of how the use of a robotic tool can make the study of the geology of Mars possible.
Grade Levels: 4th - 8th
Students will learn to make scientific observations using an edible Rock Abrasion Tool (RAT).
- Have the students work in teams of two.
- Sprinkle the bottom of the muffin cup with the cinnamon-sugar mixture.
- Place the fig bar in each mixture-sprinkled muffin cup. Use different flavors of fig bars, if you have them available. Take the fig bar and press each exposed fig side of the bar into the cinnamon-sugar mixture to cover the exposed filling on the sides of the cookie. (Note: If a variety of fig bar flavors are being used, this task can be done by the teacher prior to the distribution of the fig bars to the students to add more of a discovery component to the lesson. Just don't do this too far in advance unless you cover the cookies or the cookies will dry out and be hard to drill.)
- Sprinkle the top of the fig bar with the cinnamon-sugar mixture so the top surface of the cookie is also covered with the mixture (Mars dust!)
- Give each student team a pretzel. This is their Rock Abrasion Tool (RAT).
- Each student will observe the undisturbed "rock" before the RAT drilling begins and record observations such as color, texture, size, and surface features of the rock on the Student Activity Sheet.
- In determining the size of the sample, students should use the craft stick and a pencil to mark off the dimensions (length, width, height) of their "rock sample." Students can then use their ruler to measure their marked stick and record these measurements on their RAT Student Activity Sheet.
- Students will then take their RAT and gently place it on the top surface of their "rock." Have them rotate the RAT a few times on the surface of the cookie, applying a very slight amount of pressure. The cinnamon mixture should erode away readily, exposing the surface of the cookie portion of the fig bar.
- Each student should observe the newly exposed region and record their observations. How is it different from the original surface?
- Notice how the Martian dust (cinnamon mixture) builds up along the edge of the drilled area, along with some of the rock surface (cookie crumbs). Students should brainstorm how they could keep the dust from the "RAT hole" and contaminating the freshly drilled rock sample.
- Have students apply slightly more pressure to the pretzel and rotate several more times to dig slightly deeper into the sample (the real RAT will only penetrate approximately 5 mm into the rock and drill a diameter of approximately 2 cm). Remove the pretzel. The students should observe the filling of the fig bar (the interior of the rock). This is representative of the pristine (fresh) rock sample in its original form. Each student should observe this new material and record their observations on the RAT Student Activity Sheet.
- Again, using the craft stick, students should measure the depth and diameter of their "RAT hole" and record their observations on the RAT Student Activity Sheet.
- Students should brainstorm as to what type of rock this might be...igneous, metamorphic, or sedimentary and justify why they think so. Here are some simple definitions of the three types of rocks or you may use your own:
- Igneous rocks: rocks that are made from molten materials that well up from inside a planetary body and cool to solidify into rock.
- Metamorphic rocks: rocks that have been changed by temperature and/or pressure.
- Sedimentary rocks: rocks that have been eroded away from their original rock type and have been deposited and accumulated to solidify into new rock.
- Assign actual rock types to be represented by specific colors. For example, the cinnamon-mixture could represent iron oxide (Mars dust), the brown-colored filling could represent basalt (iron-rich lava rock), and the cookie crust could be weathered basalt. Choose other flavored fig bars to represent other types of minerals or geological processes.
- Have the students brainstorm what kind different materials they might try for this activity - other types of cookies, etc. Will some of them work with the RAT tool, while others won't? Why or why not and how does that reflect the different levels of success with different kinds of rocks on Mars that the RAT might try to drill into?
- Have the students calculate the following:
- Volume of the entire rock sample
- Area of the circular "RAT hole"
- Circumference of the circular "RAT hole"
- Volume of the material removed from the "RAT hole"
Students should complete the RAT Student Activity Sheet which includes a diagram with labels that explain the parts of their simulated dust-covered Martian rock sample, including the part of the rock revealed by the Rock Abrasion Tool (RAT).
ASU Mars K-12 Education Program
P.O. Box 876305
Tempe, AZ 85287
Student Activity Sheet
(Microsoft Word format)