Relative Age of Landforms and Sequencing of Processes
This lab has the following objectives:
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to introduce you to Mars Odyssey THEMIS-derived imagery
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to give you practice in inferring relative ages of Martian surfaces through
crater counting and assessment of crater condition
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to give you practice in applying superposition to infer the relative sequence
of processes creating Martian landforms
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to alert you to imagery flaws that could be misinterpreted as surface features
Background
The NASA Mars Odyssey orbiter (2001+) carries the Thermal Emission Imaging
System, or THEMIS. This is a multispectral imager that offers five visible
light bands (with 19 m pixels) and ten infrared bands (with 100 m pixels). In
the IR, THEMIS picks up the emitted re-radiation of solar energy absorbed
during the day. It creates images that resemble a lit landscape but it must
be remembered that the bright areas are not reflecting sunlight but strongly
emitting IR radiation.
Your data
You can download your target image from https://home.csulb.edu/~rodrigue/mars/labs/gangeschasma.jpg.
This depicts a section of Ganges Chasma on the eastern end of the Valles
Marineris system.
Interpreting the image
Examine the different parts of this image: the flat terrain dominating the
top of the image, the scarp and large crater dominating the middle ground, and
the wide variety of deposits dominating the lower portion of the image. Note
the varying density of craters found in each area and how fresh (sharp-edged
and cup-shaped) or softened (dulled edges and flatter floors) they appear.
What is the lumpy, blocky material at the base of the scarp? What are the
flatter, striated areas fanning out from those piles? Notice the
superpositions of these fanned out deposits: They are a clue to the sequence
of events here. You will probably need to look through your introductory
physical geography or general geology textbooks to figure out what those
features are and what the striations indicate. Keep an eye out for artificial
patterns that indicate camera or data-transmission hiccups.
Lab report
Write a brief lab report interpreting this landscape.
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What is the oldest area (P, C, or L)? What makes you think so?
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Identify two examples of young craters and generally describe their location
within the image. What makes you think they are younger?
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Identify and describe the locations of two examples of older craters. What
convinces you they have been around a while?
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Which geomorphological process is creating the scarp? How does it appear to
operate (why is the scarp not a straight line)?
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Which of the debris features is the youngest? Why do you think so?
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Identify at least two of the same type of features that are older than this.
what makes you think so? (pay attention to superposition, striations, and how
eroded the scarp face above it is)
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What are those striations? How do they develop?
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Identify (locate) two artifacts of the imaging process that could lead to
misinterpretation of the landscape: one is a data transmission problem and
the other is probably dust on the lens.
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Brownie point: Using Google Mars,
try to figure out where this scarp/crater/plateau complex is.
![[ image of Mars ]](https://home.csulb.edu/~rodrigue/mars/marsatlas.gif)
