Sublimation of COSublimation of CO22 Ice on Mars Ice on Mars

The sublimation rate of CO2 on Mars is currently unknown and can offer a valuable addition to any research done on Mars, including the explanation of dark spots1 and sublimation of CO2 ice on the polar ice caps2.

Figure 1Jets on Martian Polar Cap1

CONDITIONS

The purpose of this project is to obtain the sublimation rate of CO2 ice on Mars under various conditions.

•Is there a sublimation rate difference between grain sizes of CO2 ice?•Is there a sublimation rate difference if Martian equivalent soil dust covers different grain sized CO2 ice?•Can these rates explain the observed rates of polar recession on Mars during the summer season?

RESULTS

K.F. White1,2, D.W.G. Sears2,3, V. Chevrier2 , K.L. Bryson2

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 72071

•CO2 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 CO2 ice (Figure 3) and two having cylinder shaped solid pieces of CO2 ice (Figure 4).

Figure 3Gravel Sized CO2 Ice

Figure 4Solid Cylinder CO2 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 mm3/g) x (1/Surface Area)

(g/hr) = Grams lost per hour according to slope of graphed data.

(625 mm3/g) = 1 / Density of CO2

Experiments the CO2 (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: 134.75 mm/hrSample #2: 123.12 mm/hr

Average: 128.93 mm/hr

Solid Cylindrical Sublimation Rate:Sample #3: 101.91 mm/hrSample #4: 101.11 mm/hr

Average: 101.51 mm/hr

Other future plans include testing CO2 and H2O 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 CO2.

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, CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar cap, Nature, 442, 793-796, 2006 2: Byrne, S. and Ingersoll, A.P., A Sublimation Model for Martian South Polar Ice Features, Science, 299, 1051-1053, 2003

Figure 2: http://uark.edu/ua/kecklab/facilities

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Figure 2Schematic of Andromeda

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