Is it Really Sedimentary?
In-Class Activity 2_Life Hosting Rocks & Minerals
Julia Kahmann-Robinson PhD and Marjorie Chan PhD, University of Utah Department of Geology & Geophysics
Recognize sedimentary rocks on both Earth and Mars using the albedo effect.
- Last Chance Canyon, Guadalupe Mountains, NM image in Image File
- Interactive Earth Surface Albedo Map (NASA-CERES): https://ceres.larc.nasa.gov/
Present the following along with an image of Last Chance Canyon, New Mexico (Figure 1 or see Image File for Life Hosting Rocks (PowerPoint 2007 (.pptx) 22.2MB Jan20 14)):
Scenario: You are planning to hike Last Chance Canyon in the Guadalupe Mountains National Park. It is arid, no winds, and about 95F. If you had the following options for attire which would you choose and why:
- Sleeveless cotton medium blue colored shirt
- White long-sleeve cotton shirt
- Black long-sleeve cotton shirt
Discuss student response and their reasoning.
- Use the interactive Earth Surface Albedo Map (produced by NASA-CERES in Resources) and ask students to interpret the colors for albedo effect.
- Probe students as to why some "surfaces" have a higher albedo than others (ocean, desert, forest cover etc.)
- Display hand samples of sandstone, andesite, and basalt (or use the Image File for Life Hosting Rocks (PowerPoint 2007 (.pptx) 22.2MB Jan20 14)). Ask students to rank the samples according to their albedo effect.
- If students were to picture an albedo map of Mars, do they think the surface would be as variable as Earth? Overall, would Mars have a higher albedo than Earth, why or why not?
- Explain the terms of 'reflectance' and 'albedo' using the definitions below. Relate them to the discussion in the Engage section.
- Albedo- The proportion of the incident light or radiation reflected by a surface, typically that of a planet or moon.
- In Elaboration use the TES Dust Cover Index layer in JMARS to account for the fact that volcanic regions such as the Tharsis bulge appear to have high reflectivity. While much of the terrain is actually basaltic in composition, dust cover gives the illusion of a highly reflective surface.
Use the TES Dust Cover Index layer in JMARS to account for the fact that volcanic regions such as the Tharsis bulge appear to have high reflectivity. While much of the terrain is actually basaltic in composition, dust cover gives the illusion of a highly reflective surface.
Explore TES imagery in JMARS and understand the reflectance.
- Add the MOLA colorized elevation map for use as context if desired.
- Add New Layer –> Maps By Instrument –> TES –> TES-Albedo –> View graphic data.
- Zoom to a window (2 or 4) that allows you to differentiate familiar terrain. You can change the transparency of the TES-Albedo map to see the underlying MOLA colorized map to find major geographic regions of interest.
- Discuss with your students the results of the albedo map. Is anything surprising to them (i.e. Why are basalt/volcanic regions having high reflectivity? See Explanation)? What could distort the results?
- Do students find that albedo maps are a good indicator of lithology?
Go to the "Kepler: Light Grapher" web page: http://kepler.nasa.gov/education/ModelsandSimulations/lightgrapher/
Using the Light Grapher software and a webcam, measure the amount of light reflected by basalt vs sandstone. This can be done by the following steps:
- Go to the Kepler: Light Grapher web page and click on "Run LightGrapher".
- Hold the basalt rock in the camera field of view within the circle of LightGrapher.
- Make sure that the data capture time is set at 30 seconds then click on "Capture Data". This will begin measuring the amount of light reflected by the basalt.
- Keep the basalt in the field of view for ~15 seconds then switch to the sandstone for the next 15 seconds. Make sure that the measurement distance for each rock is the same.
- This will generate a graph that shows the light detected over the 30 second interval.
- See how students can correlate this activity with albedo as an analogy.
- You may use other objects with varying color/reflectivity.
An example of results obtained from this procedure can be found below as well as in the module Image File (PowerPoint 2007 (.pptx) 22.2MB Jan20 14)