In-Class Activity 1_Life Hosting Rocks & Minerals
Julia Kahmann-Robinson PhD and Marjorie Chan PhD, University of Utah Department of Geology & Geophysics
Explain why clay soils expand and discern where clays might be present on Mars.
Observe the class demonstration or video [http://www.youtube.com/watch?v=ACpuYED9WkU] and answer the following questions.
- According to the demo/video, why is the soil expanding?
- How is the bulk density changing? What is this change indicating?
The molecular level- Utilize the diagram to the right to help students understand how clays are made up of stacked layers.
Have students answer the following questions:
- In Figure 1a, how are the water molecules influencing the structure?
- Why do you think the water attracts to the clay rather than the sand of the sandy loam (consult Figure 1b)?
Share the following information about clays with students:
- Clays are expandable due to their layer charge. The higher the layer charge (for example montmorillonite or bentonite) the more the clay will expand.
- The interlayer (the charged layer) attracts water molecules allowing for the clay to expand
- Clays are commonly formed in the pedogenic, hydrothermal, or acid lake environment on Earth.
Given your understanding of clays now, if clays [Na0.2Ca0.1Al2Si4O10(OH)2(H2O)10] are observed on Mars....what does this mean?
Where might you look to find clays on Mars (what kind of features)? Hint: consider their environment of formation, do we have evidence for their presence on Mars?
Watch this video about clay minerals on Mars: http://www.youtube.com/watch?v=cmc54EPvMZE