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40th Lunar and Planetary Science Conference (2009) 1088.pdf

SAMPLE ANALYSIS AT (SAM) INSTRUMENT SUITE FOR THE 2011 . P. R. Mahaffy1, M. Cabane2, P. G. Conrad3, C. R. Webster3, and the SAM Team, 1NASA God- dard Space Flight Center, Code 699, Greenbelt, MD 20771 ([email protected]), 2Service d’Aéronomie, Institut Pierre Simon Laplace, Université Pierre et Marie Curie-Paris VI, UMR 7620, CNRS, Verrières-le-Buisson, France, 3Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109

Introduction: The Sample Analysis at Mars valves, gas manifolds with heaters and temperature (SAM) suite of instruments is designed to explore the monitors, chemical and mechanical pumps, carrier gas past or present habitability of Mars by exploring car- reservoirs and regulators, pressure monitors, pyrolysis bon chemistry through a sensitive search for organic ovens, and chemical scrubbers and getters. The Mars componds [1], the chemical state of light elements atmosphere is sampled by CSPL valve and pump ma- other than , and isotopic tracers of planetary nipulations that introduce an appropriate amount of gas change. The science goals of this investigation are through an inlet tube to the SAM instruments. The listed in Table 1. Nine other instrument based investi- solid phase materials are sampled by transporting gations hosted on the Mars Science Laboratory will finely sieved materials to one of 74 SMS sample cups also support the ambitious goals of the mission [2] to that can then be inserted into a SAM oven and ther- quantitatively assess habitability through a series of mally processed for release of volatiles. chemical and geological measurements. With the SAM integration presently complete, this report will provide a summary of the science goals and measurement ca- pabilities of this suite. Table 1. Goals of the SAM Investigation that ad- dress present and past habitability Survey carbon compound sources and Goal 1 evaluate their possible mechanism of forma- tion and destruction Search for organic compounds of biotic and Goal 2 prebiotic importance including Reveal the chemical and isotopic state of Goal 3 elements (i.e. N, H, O, S, C and others) that are important for as we know it Evaluate the habitability of Mars by study- Goal 4 ing its atmospheric chemistry and the com- position of trace species that are evidence of interactions between the atmosphere and soil Understand atmospheric and climatic evolu- Goal 5 tion through measurements of noble gas and light element . SAM Instruments and Supporting Subsystems: SAM (Figure 1) consists of three instruments and two major supporting subsystems. The instruments are a Quadrupole Mass Spectrometer (QMS), a Gas Chro-

matograph (GC), and a Tunable Laser Spectrometer Figure 1. The layout of SAM’s instruments and major (TLS). The QMS and the GC can operate together in a supporting subsystems is illustrated in the top portion of GCMS mode for separation (GC) and definitive identi- this figure and the flow of gas and sample to the instru- fication (QMS) of organic compounds. The TLS ob- ments illustrated in the lower panel. tains precise ratios for C, H, and O in carbon The SAM Quadrupole Mass Spectrometer. The dioxide and and measures trace levels of meth- QMS analyzes both both atmospheric samples and ane and its carbon 13 isotope. The supporting systems gases thermally-evolved from solid phase samples to are a sample manipulation system (SMS) and a sub ppb sensitivity. QMS is the primary detector for Chemical Separation and Processing Laboratory the GC and can operate in static or dynamic mode. Its (CSPL) that includes high conductance and micro mass range is 2-550 and its ion detector dy- 40th Lunar and Planetary Science Conference (2009) 1088.pdf

namic range >1010 with both a channeltron pulse into the CSPL manifold enables diurnal and seasonal counting electron multiplier and a Faraday Cup. The variations to be measured over the course of the two crosstalk between adjacent peaks is greater than 106 year mission by the QMS and the TLS. In addition, which enables all the isotope measurements of interest specialized gas sampling experiments include a meth- to be made without crosstalk interference. ane enrichment experiment to increase the density of The SAM Gas Chromatograph. The GC separates methane in the TLS for improved precision of the 13 12 complex mixtures of organic compounds into molecu- C/ C measurement in CH4. Likewise, the noble gas lar components for QMS analysis and for detection of enrichment experiment separates out chemically reac- compounds with the thermal conductivity detectors on tive gases to provide noble gas enriched samples to the 5 of the 6 columns. Before analysis by the QMS, the 6 QMS for static and isotope and columms of the GC allow the separation of a wide noble gas elemental ratio analysis. Both of these ex- range of species, including permanent and noble gases, periments utilize chemical getters and scrubbers to light and heavy volatile organic compounds, pyrolysis separate out the interfering gasses. and derivatization products, and enantiomers. The de- Calibration Sequences: A mixture of several cali- tection limit of the combined GC/QMS system exceeds bration gases is brought to Mars in SAM to be used at the part per billion mission requirement for organic regular intervals during the mission. The calibration detection. gas cell includes N2, CO2, Ar, and a Xe mix that is The SAM Tunable Laser Spectrometer. The TLS is heavily spiked with 129X to insure that there is no dan- a two channel Herriott cell design spectrometer that ger of mistaking this gas for xenon if a leak provides high sensitivity, unambiguous detection of were to develop in the microvalve seat separating the targeted species (CH4, H2O, and CO2) and the selected gas from the inlet manifold. In addition, three fluoro- isotope ratios 13C/12C, 18O/16O, and 17O/16O in carbon carbon compounds are included in this cell so the per- dioxide, D/H in water, and 13C/12C in methane. The formance of the GCMS system can be evaluated over direct detection methane sensitivity for atmospheric the course of the mission. These calibration gases will gas ingested into the TLS Harriott cell is < 1 ppb and be used in several SAM comprehensive performance the detection limit can be greatly reduced by methane tests to be carried out after SAM is delivered to JPL for enrichment in SAM’s CSPL. integration into the MSL rover. TLS carries on-board 2 Analysis of Solid Samples: Solid sample analysis, isotopic reference gas cells for both CH4 and CO . atmospheric sampling, and calibration sequences will Organic Check Material: The possibility of a be interleaved over the course of the surface mission. false positive detection of organic molecules on Mars The solid sample sequences include even after careful attention to MSL and SAM contami- A. Direct evolved gas analysis followed by nation control [3], will be addressed by use several GCMS analysis and times during the mission of an organic check material B. Chemical derivatization followed by GCMS (OCM). In this experiment a very pure amorphous analysis silica impregnated with a distinctive set of synthetic C. Combustion of refractory organics followed fluorocarbons will be sampled by the MSL drill and by isotopic analysis in the TLS rock powdering system and delivered into the SAM In sequence A several tens of cubic millimeters of inlets for GCMS analysis. The sample processing will powdered sample are deposited into one of the quartz directly mimic that of a Mars rock and possible terres- cups in the SMS and heated with a programmed ramp trial cross contamination of this sample from the rover from ambient to ~1100 oC while continuously sam- during the sample processing and transport process pling evolved gas with the QMS. A portion of the revealed. The OCM experiment will be most useful evolved gas can be directed at any time through a hy- following a tentative detection of organics in a Mars drocarbon trap for later release and analysis by chro- rock sample by SAM. Six such experiments can be matography with the GC and the QMS. In sequence B carried out over the course of the mission. the sample is introduced into a solvent that also con- References: [1] Mahaffy, P.R., Space Sci. Rev. tains a chemical derivatization agent that is selected to 135, 255 (2008). [2] Crisp, J. et al., Ground Truth from transform polar molecules such as carboxylic acids Mars conference contr. 1401, 24 (2008). [3] ten Kate I. into volatile species that can be analyzed by GCMS. L. et al., Astrobiology 8, 571 (2008). Sequence C utilizes an gas reservoir to com- Acknowledgement: Funding for the SAM devel- bust the refractory carbon in a sample into CO2 whose opment was provided by NASA through the Mars Sci- 13C/12C can be analyzed by the TLS. ence Laboratory at the Jet Propulsion Laboratory and Analysis of Atmospheric Samples: Regular di- for the GC from the CNES. rect atmospheric sampling by ingestion of a gas sample