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Downloaded From Experimental characterization and in situ measurements of chemical processes in the martian surface environment Quinn, R.C. Citation Quinn, R. C. (2005, May 18). Experimental characterization and in situ measurements of chemical processes in the martian surface environment. Retrieved from https://hdl.handle.net/1887/2313 Version: Corrected Publisher’s Version Licence agreement concerning inclusion of doctoral thesis in the License: Institutional Repository of the University of Leiden Downloaded from: https://hdl.handle.net/1887/2313 Note: To cite this publication please use the final published version (if applicable). Experimental characterization and in situ measurements of chemical processes in the martian surface environment Proefschrift ter verkrijging van de graad van Doctor aan de Universiteit Leiden op gezag van de Rector Magnificus Dr. D. D. Breimer, hoogleraar in de faculteit der Wiskunde en Natuurwetenschappen en die der Geneeskunde, volgens besluit van het College voor Promoties te verdedigen op woensdag 18 Mei 2005 te klokke 15:15 uur door Richard Charles Quinn geboren te New York, USA Promotiecommissie Promotor: Prof. Dr. P. Ehrenfreund Referent: Prof. Dr. C. Chyba (Stanford University, USA) Overige leden: Prof. Dr. J. Fraaije Prof. Dr. R. A. Mathies (University of California, Berkeley, USA) Dr. F. J. Grunthaner (JPL, California Institute of Technology, USA) Dr. C. P. McKay (NASA Ames Research Center, USA) Dr. A. P. Zent (NASA Ames Research Center, USA) Dr. O. Botta (ISSI, Switzerland) Cover: Photo of the Atacama Desert, which is located along the northern Chilean pacific coast from 30° S to 20° S latitude. This image was taken near the Mars Oxidant Instru- ment deployment site which is located at 24°4'10" S, 69°51'59" W. Contents 1 Introduction ........................................................................................................... 1 1.1 Results from the NASA Viking Mars missions ........................................... 2 1.2 Mars oxidant hypotheses ............................................................................... 4 1.3 Results from the NASA Mars Exploration Rovers ...................................... 5 1.4 Acid-base soil chemistry on Mars ................................................................ 7 1.5 In situ measurement technologies ................................................................ 8 1.6 The Atacama Desert as a Mars analog test site ............................................ 10 1.7 Outline and conclusions of this thesis .......................................................... 12 2 Peroxide-modified titanium dioxide: a chemical analog of putative martian soil oxidants .......................................... 19 2.1 Introduction ................................................................................................... 20 2.2 Experimental ................................................................................................. 22 2.2.1 Synthesis of titanium dioxide (anatase) ......................................... 22 2.2.2 Decomposition of aqueous organics .............................................. 23 2.2.3 Oxygen release upon humidification ............................................. 24 2.3 Results and Discussion ................................................................................ 25 2.3.1 Carbon dioxide release .................................................................. 25 2.3.2 Oxygen release .............................................................................. 28 2.4 Conclusions ................................................................................................. 31 3 The photochemical stability of carbonates on Mars ......................................... 35 3.1 Introduction ................................................................................................. 36 3.1.1 Formation of carbonates on Mars ................................................. 36 3.1.2 The effect of UV light on carbonate formation and stability ........ 37 3.2 Materials and methods ................................................................................. 37 3.2.1 Experimental apparatus ................................................................. 37 3.2.2 Sample preparation ........................................................................ 38 3.2.3 Experimental procedure ................................................................. 39 3.2.4 Calibrations .................................................................................... 40 3.3 Results .......................................................................................................... 41 3.4 Discussion .................................................................................................... 42 i 3.4.1 Thermodynamic effects of CO2 partial pressure ............................ 43 3.4.2 Effects of UV light on carbonate stability ...................................... 44 3.4.3 UV decomposition at quantum efficiencies less than 3x10-8 ......... 46 3.5 Conclusions ................................................................................................... 48 4 Aqueous decomposition of organic compounds in the Atacama Desert and in martian soils ........................................................ 53 4.1 Introduction ................................................................................................... 53 4.2 Methods and materials .................................................................................. 56 4.2.1 Atacama samples ............................................................................ 56 4.2.2 Substrate induced organic decomposition experiments .................. 57 4.3 Results ........................................................................................................... 58 4.4 Discussion ..................................................................................................... 60 4.4.1 Formate decomposition kinetics ..................................................... 60 4.4.2 Surface catalyzed organic decomposition ...................................... 62 4.4.3 Oxidant chemistry in aqueous systems on Mars ............................ 64 4.5 Conclusions .................................................................................................. 65 5 Dry acid deposition and accumulation at the Viking lander sites and in the Atacama Desert, Chile ........................................................................ 71 5.1 Introduction .................................................................................................. 72 5.2 Experimental ................................................................................................ 74 5.2.1 Atacama samples ........................................................................... 74 5.2.2 Atacama sample measurements ..................................................... 75 5.2.3 Viking labeled release experiment data reduction ......................... 75 5.3 Results and Discussion ................................................................................. 77 5.3.1 pH response of Atacama soils ........................................................ 77 5.3.2 pH responses in the Viking labeled release experiment ................. 79 5.3.3 Acid deposition and accumulation ................................................. 82 5.3.4 Adsorbed water, effective soil pH, and soil biopotential ............... 84 5.4 Summary and Conclusions ........................................................................... 86 6 Mars atmospheric oxidant sensor (MAOS): an in situ heterogeneous chemistry analysis ........................................................ 91 6.1 Introduction ................................................................................................... 91 6.2 Scientific goals and objectives ...................................................................... 92 6.2.1 The possibility of martian life, past or present ............................... 92 6.2.2 The Viking biology results ............................................................. 94 6.6.3 The nature of martian oxidants ....................................................... 94 6.2.4 MAOS’ scientific objectives .......................................................... 96 6.3 Hardware implementation ............................................................................ 98 ii 6.3.1 Operating principles ...................................................................... 98 6.3.2 Instrumentation .............................................................................. 98 6.3.2.1 Sensing films ............................................................... 100 6.3.2.2 Seals ............................................................................ 101 6.3.2.3 Filters .......................................................................... 101 6.3.3 Performance characteristics .......................................................... 101 6.3.4 Analysis ........................................................................................ 103 6.3.5 Calibration .................................................................................... 103 6.3.6 Interferences ................................................................................. 104 6.4 Summary ..................................................................................................... 104 7 Detection and characterization of oxidizing acids in the Atacama Desert using
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