Sublimation of CO 2 Ice on Mars The sublimation rate of CO 2 on Mars is currently unknown and can offer a valuable addition to any research done on Mars, including the explanation of dark spots 1 and sublimation of CO 2 ice on the polar ice caps 2. Figure 1 Jets on Martian Polar Cap 1 CONDITIONS The purpose of this project is to obtain the sublimation rate of CO 2 ice on Mars under various conditions. Is there a sublimation rate difference between grain sizes of CO 2 ice? Is there a sublimation rate difference if Martian equivalent soil dust covers different grain sized CO 2 ice? Can these rates explain the observed rates of polar recession on Mars during the summer season? RESULTS K.F. White 1,2, D.W.G. Sears 2,3, V. Chevrier 2, K.L. Bryson 2 1 Ball State University, Muncie, IN 46947, 2 Arkansas Center for Space and Planetary Science, Fayetteville, AR 72071, 3 Arkansas University Department of Chemistry and Biochemistry, Fayetteville, AR CO 2 atmosphere at 7 mbar Atmospheric temperature: - 10°C CO ice forms: solid cylinder, broken up gravel sized, and finely crushed powder. Thus far, there have been four experiments. Two having gravel sized pieces of CO 2 ice (Figure 3) and two having cylinder shaped solid pieces of CO 2 ice (Figure 4). Figure 3 Gravel Sized CO 2 Ice Figure 4 Solid Cylinder CO 2 Ice By using the slope of the graphs for the g/min rate and converting it into g/hr, the following formula was used along with the measured surface area over time: (g/hr) x (625 mm 3 /g) x (1/Surface Area) (g/hr) = Grams lost per hour according to slope of graphed data. (625 mm 3 /g) = 1 / Density of CO 2 Experiments the CO 2 (solid, gravel size), sample was contained in a small beaker for purposes of measuring the surface area before and after accurately. INTRODUCTION OBJECTIVES PROCEDURE PRELIMINARY RESULTS FUTURE PLANS ACKNOWLEDGEMENTS Gravel Sized Sublimation Rate: Sample #1: mm/hr Sample #2: mm/hr Average: mm/hr Solid Cylindrical Sublimation Rate: Sample #3: mm/hr Sample #4: mm/hr Average: mm/hr Other future plans include testing CO 2 and H 2 O mixtures as well as adding 1-3 mm of Martian equivalent dust over the ice to measure its affects upon the sublimation rate. Also this research is to attempt to explain the origin of the dark spots on Mars, determining of jets are possible. Using the Andromeda Chamber (Figure 2) at the W. M. Keck Laboratory for Space Simulation at the University of Arkansas, Mars like conditions were created and maintained over an average experimental duration of 1hr 30min with various conditional samples of CO 2. Experimental chamber provided and funded by the Arkansas Space and Planetary Science Department of University of Arkansas. 1: Kieffer, H.H., P.R. Christensen, and T.N. Titus, CO 2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar cap, Nature, 442, , : Byrne, S. and Ingersoll, A.P., A Sublimation Model for Martian South Polar Ice Features, Science, 299, , 2003 Figure 2: Figure 2 Schematic of Andromeda Chamber