Did it Rain on Mars? Analysis of Valley Networks on Mars in an Intro Geo Course
Summary
Students investigate the question of whether it might have rained on Mars by doing an activity based on an article by Hynek and Phillips (2003). Students do a simple drainage basin analysis based on Hynek and Phillips' maps, calculate drainage densities, and compare results to data for rain-fed arid regions on Earth.
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Context
Audience
Intro geo, geomorphology, planetary geology.
Skills and concepts that students must have mastered
This activity assumes virtually no prior knowledge on the part of students. The instructor can easily provide appropriate background at the time of the activity on the Viking mission, on images obtained from orbit by the Mars Orbiter Camera, and on elevation data obtained with the Mars Orbiter Laser Altimeter.
How the activity is situated in the course
Goals
Content/concepts goals for this activity
To evaluate whether ancient Mars valley networks might have been produced by rainfall analyzing how similar they are to valley networks on Earth that we know are produced by rainfall. Students complete simple drainage basin analyses and compare their results with terrestrial data.
Higher order thinking skills goals for this activity
- analysis of data
- synthesis of data from a variety of sources
- critical evaluation of pre-existing hypothesis
- evaluation of uncertainties
Other skills goals for this activity
Description of the activity/assignment
Some of the Viking images sent back from Mars in the 1970s show tantalizing evidence of dendritic valley networks in some of the oldest terrains on the planet. One of the big questions ever since has been whether it might have rained early in Mars history.
One of the ways of deciding whether the Mars valley networks might have been produced by rainfall is to find out how similar they are to valley networks on Earth, which we know are produced by rainfall. The standard method for analyzing drainage basins is comparison of the number of drainage segments per square kilometer (drainage density) and how extensively branched the network is (stream order).
In this exercise, students calculate stream order for valley segments mapped by Hynek and Phillips (2003) using MOC/MOLA data. Students then use data on valley segment length and drainage basin area from Hynek and Phillips (2003) to calculate drainage density. They compare stream order and drainage density for the Mars site with similar calculations for areas on Earth and evaluate the question of whether valley networks on Mars might be consistent with rainfall on an early Mars, and what the uncertainties and limitations are in their conclusions.
One of the ways of deciding whether the Mars valley networks might have been produced by rainfall is to find out how similar they are to valley networks on Earth, which we know are produced by rainfall. The standard method for analyzing drainage basins is comparison of the number of drainage segments per square kilometer (drainage density) and how extensively branched the network is (stream order).
In this exercise, students calculate stream order for valley segments mapped by Hynek and Phillips (2003) using MOC/MOLA data. Students then use data on valley segment length and drainage basin area from Hynek and Phillips (2003) to calculate drainage density. They compare stream order and drainage density for the Mars site with similar calculations for areas on Earth and evaluate the question of whether valley networks on Mars might be consistent with rainfall on an early Mars, and what the uncertainties and limitations are in their conclusions.
Determining whether students have met the goals
Student written work on the assignment completed in class.
More information about assessment tools and techniques.Teaching materials and tips
- Activity Description/Assignment (Microsoft Word 3.7MB Apr27 06)
- Instructors Notes (Microsoft Word 777kB Apr27 06)
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Other Materials
- Large format image for printing. (a 1951 by 3187 pixel WebP)
Supporting references/URLs
Carr, M.H., 1995, The Martian drainage system and the origin of valley networks and fretted channels: Journal of Geophysical Research, v. 100, p. 7479-7507.
Carr, M.H. and Chuang, F.C., 1997, Martian drainage densities: Journal of Geophysical Research, v. 102, p. 9145-9152.
Hynek, Brian M. and Phillips, Roger J., 2003, New data reveal mature, integrated drainage systems on Mars indicative of past precipitation: Geology, v. 31, no. 9, p. 757-760.
Carr, M.H. and Chuang, F.C., 1997, Martian drainage densities: Journal of Geophysical Research, v. 102, p. 9145-9152.
Hynek, Brian M. and Phillips, Roger J., 2003, New data reveal mature, integrated drainage systems on Mars indicative of past precipitation: Geology, v. 31, no. 9, p. 757-760.