AAS 207th Meeting, 8-12 January 2006
Session 4 Solar System
Poster, Monday, 9:20am-7:00pm, January 9, 2006, Exhibit Hall

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[4.03] Ages of three martian surfaces using crater count isochrons and Mars Global Surveyor images.

D. Themistokleous, M.N. Hayes-Gehrke (University of Maryland)

The extensive image database of the Mars Global Surveyor satellite has recently allowed astronomers to make more accurate determinations of the ages of the surfaces on Mars. As part of this effort, we chose to determine the ages of three areas on Mars: Syrtis Major (lat. 15 deg. N, long. 300 deg. W), Thaumasia (45 deg. S, 90 deg. W), and Tharsis (15 deg. N, 120 deg. W). We selected eight images from the Mars Global Surveyor MOC Wide Angle Image database (available at http://www.msss.com/moc_gallery/) for each area. We tallied the number of craters in each image and measured the average diameter of each crater. We categorized the craters by size, and then calculated the number of craters per area in each size bin. We plotted these data on the age isochrons of Hartmann (Meteoritics & Planetary Science, 1999, 34, 167) for Mars and then visually inspected each plot to determine the best-fitting age isochron for each area. We will present the results of this analysis for each region. We expect the surface in the Thaumasia region to be the oldest, since it is located in a heavily-cratered region of the southern hemisphere. The age of the surface in the Tharsis region is rather uncertain since we do not know how recently volcanic activity has resurfaced the region. The Syrtis Major region is well-known for its changing surface dust distribution, which fills in craters and may make the age determination surprisingly low.

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