1. 1 Tolstoj Quadrangle Mark Robinson and Brett Denevi Arizona State University Scott Murchie, APL MESSENGER GDG Telecon 11/20/2007

2. 2 Quick Reminder From Spudis and Guest in Mercury (1988)

3. 3 http://ser.sese.asu.edu/M10/GAZET/index.html Tolstoj Quadrangle (H8)

4. 4 Main features Intercrater plains (light orange color) Tolstoj Basin (350 km, 3.97 Gyr) Southern portion of Caloris (1300 km, 3.77 Gyr) –Odin formation (medium blue) similar to Alpes of Imbrium Tolstoj, Tir, Budh (peach color) and Caloris smooth plains occupy much of the region Mozart - fresh, large (285 km) crater on terminator Complex structural features Budh Tir Planitia Tolstoj Mozart Caloris Hummocky plains Intercrater plains Tolstoj rim material Smooth plains

5. 5 Significant Features Smooth Plains (Tolstoj, Tir, Budh) Low albedo, blue material around Tolstoj High albedo enigmatic crater floor deposits (Tyagaraja, Zeami, Balzac) Structural features (wrinkle ridges, lobate scarps)

6. 6 Smooth plains Tir, Tolstoj, and Budh planitia all radar bright compared to surrounding intercrater plains (Harmon et al., 2004) –Opposite of lunar mare, which are radar dark due to Fe, Ti –Compositional differences between smooth plains and surroundings? –Rougher small-scale surface texture than surroundings? Lots of small bright craters in Budh planitia (0.2-0.3) Budh Planitia

7. 7 Low albedo region around Tolstoj Tolstoj smooth plains overlie dark material (below one std deviation of average Mercury albedo) High UV/Orange ratio (among bluest material on planet), enriched in opaques (Robinson and Taylor, 2001) Ancient crustal material or secondary process such as pyroclastic? Arrows and X indicate low reflectance material, image 675 km wide.

8. 8 Enigmatic crater floor materials Good examples of these materials in Tolstoj quad Albedos up to ~0.3 Dark halo? Mentioned in literature… Dzurisin (1977) - local physio-chemical alteration along impact-induced fractures Schultz (1977) - compositional or endogenic modification possible causes of color differences Tyagaraja Zeami Balzac

9. 9 Structural Features Chock full of wrinkle ridges in smooth plains A few lobate scarps Local compression, plains contained in broad depressions Global compression result in lobate scarps? Smooth plains, wrinkle ridges in Tostoj Quadrangle (Tir), 800 km wide

10. 10 Tectonics, Geology, Image White worms indicate Wrinkle ridges Black with triangle show Lobate scarps Thanks to T. Watters!

11. 11 Tolstoj Quad questions for MESSENGER Composition of smooth plains? Why are the smooth plains radar bright? Why is the Tolstoj material so blue? What are the weird crater floor deposits? Origin of structural features? Relative Ages? M1 coverage of Tolstoj Quad