Is it a Soil?
In-Class Activity 2_Weathering and Soils
Julia Kahmann-Robinson PhD and Marjorie Chan PhD, University of Utah Department of Geology & Geophysics
Identify Earth soil horizons and extrapolate what characteristics of soil would be observable on Mars.
Study Figure 1 (or the image provided by your instructor).
- What part of this picture is a soil and why?
- What criterion are students using to define a soil?
- Brainstorm at least four factors that create and form soil on Earth.
- Factor 1:
- Factor 2:
- Factor 3:
- Factor 4:
Identifying Soil Horizons
In Figure 2 draw lines and/or labels at horizon boundaries. Indicate if any layers are not present.
O Horizon- thick organic-rich layer
A Horizon- relatively thin organic layer with rooting
E Horizon- leached layer (not always present)
B Horizon- mineral layer
C Horizon- Parent material
1. What characteristics of this profile might you observe on Mars? Can you observe it remotely? What do you think makes that yellow layer "yellow"?
- The 5 soil-forming factors are: (1) parent materials (2) time (3) biota (4) topography and (5) climate
- In order for a soil to be classified as a soil it must have evidence of life and/or plant material
- With regard to general soil horizons: the O-horizon must have a thick layer of organic matter, an A-horizon typically has an abundance of roots and some organic matter, an E-horizon is a leached horizon (of most base-forming cations), the B-horizon is a mineral layer where minerals accumulate, the C-horizon has some characteristics of pedogenesis but still may show structures of the parent material such as bedding, the R-horizon is the parent material.
Observe Figure 3 from Mars at Mawrth Vallis, one of the landing site considerations of MSL Curiosity (captured via JMARS):
- What observations can you make of this image?
- What do you think the changes in color represent?
- Do changes in color follow any other pattern you can discern?
- If you had the opportunity to test the surface of Mars at Mawrth Vallis, what evidence would you look for to identify if soils are present.
- If soils were (are) present at Mawrth Vallis, what horizons would be most likely preserved?