Rodrigue Brings Mars Sabbatical Back To Her Classroom WorkPublished: December 15, 2010
Geography’s Christine Rodrigue, a member of CSULB since 1999, has just returned from an out-of-this-world sabbatical. “Mars: A Regional Areography” describes her system of regionalizing the red planet’s surface.
She first began to bone up on Mars in 2001 as part of a seemingly unrelated research project on technological hazards in the space program. NASA asked her for advice on improving risk communication for the then-planned Mars Sample Return Lander (MSRL). During a 2002 sabbatical, she began to read about Mars planetary research.
“It was a little overwhelming at first,” she said. ”But I began to develop a solid understanding of Mars science. By the time the MSRL succumbed to budget cuts, I had acquired all this information about Mars but I had no project left to apply it to. So I asked myself, ‘Why don’t I create a class before I forget it all?’ In 2007, I launched ‘The Geography of Mars’ as a Special Topics course in Geography, which attracted a dozen students, more than the usual special topics course.”
While developing the class, she noticed other geographers working on Mars and in 2008 reached out to about 100, some of whom studied statistical applications. “I love stats,” she said. “I teach statistics. And I found there were all these issues in Mars research that I could make a contribution to.” This group eventually became the Mars Geography Network.
Rodrigue wanted her CSULB students to acquire a sense of where on Mars certain features were located and their spatial relationships. She felt it was necessary to create a regional geography scheme for the planet. “I adapted the ‘orders of relief’ pattern used in basic geography texts,” she explained. The outcome was a nested five-level plan that laid out the face of Mars (if not the Face on Mars!). The first order was the divide between the smooth northern lowlands and the rough southern highlands; the second covered huge impact, rifting, volcanic, glacial and fluvial features; and the third focused on what defined various Martian geological epochs (varying crater density patterns). The fourth order counted individual landslides, craters, yardangs, dune fields and drainage systems. The fifth order described very local features, such as trenches made by rovers, rock abrasion pits (“RAT holes”) and “blueberries.” She went on to address the topic of “Orders of Relief and the Regional Geography of Mars” before the Association of American Geographers in 2008.
Rodrigue came to believe during her sabbatical that Mars and other extraterrestrial objects are within the purview of geography, that geographers can contribute meaningfully to Mars research and that the study of Mars can benefit geography. By using field-based analogues of Earth landscapes, Earth-bound geographers can generate hypotheses for testing with Mars data. “Mars can be used to deepen Earth understanding among our students through the comparison and contrast it affords,” she said.
Her sabbatical saw her interest grow in secondary craters, a topic she addressed before the Association of American Geographers in Washington, D.C., in April where she spoke on “Detection of Secondary Craters to Improve Martian Surface Regionalization through the Crater Size-Frequency Distribution.”
The only current way to estimate regional surface ages on Mars is through the use of an impact crater size-frequency distribution system. The ideal size-frequency distribution works until saturation occurs (where crater density is so great that one more impact obliterates all traces of an older crater). Ages of surfaces at saturation cannot be characterized any better than “very old.”
As higher resolution imagery began to pour in from Mars, scientists counted so many small craters in the largest scale images that the numbers began to show anomalies in the diameter-frequency relationship that affected the age research. “Smaller craters were over-represented,” said Rodrigue. “One explanation was secondary cratering: debris from an impact that had shot outward and upward, impacting some distance from the primary crater, often forming ray-shaped concentrations, like asterisks, ringing a primary crater. So, a lot of the smallest craters could well not be from the space impactors used to calibrate Martian surface ages.”
Rodrigue used the relation of one crater to another in terms of size and position to adjust for secondary impact distortions. She picked an area of Mars hammered with craters and identified their exact centers and then their spatial relationships with one another. “This is important because there are no human field geologists on Mars collecting rock samples and dating them in labs,” she said. “There is no way to find absolute dating on the Martian surface. The only way to age the Martian surface is to count craters.” So, any distortion in the diameter-frequency relationship can distort aging the landscape surfaces.
Rodrigue is pleased with her discovery. ”It’s really cool that I may have found a way of picking out secondary craters,” she said. “I found I could count the number of craters in a particular picture that are probably linked together as secondary crater rays. By taking them out of the original data base, it could improve estimated landscape ages by only using original craters.”
Rodrigue has her own web page at www.csulb.edu~rodrigue. She earned an A.A. in French and German from Pierce College, a B.A. and M.A. in geography from Cal State Northridge and a Ph.D. in geography at Clark University.
Her research has changed the way she sees Mars. “Mars became a real place to me,” she said. “It’s not just a red dot in the sky anymore. Once I saw the possible relevance of the old ‘orders of relief’ scheme used to regionalize landscapes on Earth in introductory geography courses, I saw I could use the same scheme to organize the surface of Mars.”
Her original research goal sought to use Martian landscapes to improve Earth science education and geography classes and she feels she has succeeded. Her technique is to find common analogues between the two planets that bring out some quirks from planet Earth. One example is how Earth’s atmosphere features four distinct layers based on how temperatures change with altitude; Mars has only three such layers, missing the distinctive stratosphere that Earth has. Photosynthesis by Earth plants creates an abundance of oxygen here, which becomes ozone in our stratosphere. There is hardly any oxygen in the Martian atmosphere, so there’s no ozone layer and, thus, no stratosphere in the sense it’s known on Earth.
She started taking her Martian show on the road to conferences. She created a visual organization of the Martian surface which she has downloaded for others to use to help situate their work on Mars. She hunts for data bases to help her students and uses data from the Mars Exploration Rover Spirit to teach them multivariate statistics. “It worked out really well,” she recalled. “You never know before you teach a class what will work out and what won’t. I’m glad this worked.”