DETECTION OF EVOLVED CARBON DIOXIDE IN THE ROCKNEST EOLIAN BEDFORM BY THE SAMPLE ANALYSIS AT MARS (SAM) INSTRUMENT AT THE MARS CURIOSITY LANDING SITE. B. Sutter1, D. Archer2, A. McAdam3, H. Franz3, D.W. Ming2, J. L. Eigenbrode3, D. P. Glavin3, P. Mahaffy3, J. Stern3, R. Navarro-Gonzalez4, C. McKay5. 1Jacobs-ESCG Houston TX 77058, 2NASA Johnson Space Center, Houston TX 77058, 2NASA Goddard Space Flight Center, Greenbelt, MD 20771, 3Universidad Nacional Autónoma de México, México, D.F. 04510, Mexico, 4NASA Ames Research Center, Moffett Field, CA 94035. Introduction: The Sample Analysis at Mars Results/Discussion: (SAM) instrument detected four releases of carbon All four Rocknest soils had four releases of CO 2 dioxide (CO ) that ranged from 100 to 700˚C from the with peaks at 225 (peak 1), 296 (peak 2), 398 (peak 3), 2 Rocknest eolian bedform material (Fig. 1). Candidate and 488˚C (peak 4). Using Rocknest 2 data, CO re- 2 sources of CO include adsorbed CO , carbonate(s), lease masses were ~ 0.01, 0.02 0.04, and 0.03 wt% C, 2 2 combusted organics that are either derived from terres- respectively [10.8 (±1.3) µmole total CO released, 75 2 trial contamination and/or of martain origin, occluded mm3 sample volume [6] and asssuming bulk soil densi- or trapped CO , and other sources that have yet to be ty 1.7 g cm-3 (Fig. 1)]. The calculated sample mass 2 determined. The Phoenix Lander’s Thermal Evolved could change as sample delivery volume and bulk den- Gas Analyzer (TEGA) detected two CO releases (400- sity continues to be investigated. All reported C con- 2 600, 700-840˚C) [1,2]. The low temperature release centrations are preliminary and are used to constrain was attributed to Fe- and/or Mg carbonates [1,2], per- the C-bearing phases in Rocknest. chlorate interactions with carbonates [3], nanophase la 10 carbonates [4] and/or combusted organics [1]. The ud 0 high temperature CO2 release was attributed to a calci- iseR--2100 R mocaksnse 4s5t 2 um bearing carbonate [1,2]. No evidence of a high -30x103 temperature CO release similar to the Phoenix materi- 200x103 PAereaak: 31.5473e+07 Peak 4 2 Area: 1.1214e+07 al was detected in the Rocknest materials by SAM. Peak 2 The objectives of this work are to evaulte the tempera- 150 Area: 8.1671e+06 mass45 fit_mass45 ture and total contribution of each Rocknest CO re- Bkg_mass45 2 'Peak 0' leasMe aantder tihaelisr/ Mpoestshiboldes s: oTuhrcee Rs.o cknest eolian bedform spc100 PAereaak: 12.5802e+06 '''RPPPeeeesaaa_kkkm 123a'''ss45 material consists of unconsolidated sand and dusty material [5]. Four replicate Rocknest samples (< 150 50 m) were heated in SAM at a rate of 35˚C min-1 from ambient to 840˚C at a pressure of 30 mb with a He 0 carrier gas flow rate of ~1.5 sccm. Evolved gases were 100 200 300 400 500 600 700 analyzed by a quadrupole mass spectrometer (QMS) Temperature (°C) Fig. 1. Rocknest sample 2 CO (mass 45) versus temperature over the entire temperature range. The CO release 2 2 (red). Grey peaks are Gaussian fits to the oveall CO release data was fitted with a Gausian multi-peak fitting rou- 2 that sum to the blue line. Residual (light blue) is at top. tine (IGOR Pro 6.2) to quantify the contribution of each CO release to the total amount of CO . 2 2 The lowest temperature peak could mostly be at- A laboratory Setaram Sensys-Evo differential tributed physisorbed atmospheric CO . Physisorbed scanning calorimeter coupled to a Stanford Research 2 constituents are held by intermolecular forces (van der Systems Universal Gas Analyzer at NASA Johnson Waal) and are typically released at temperatures below Space Center (JSC) have been configured to operate 200˚C. The amount of of CO released (0.01 wt.% C) similar to the SAM oven/QMS system. This JSC- 2 is also reasonable for a few monolayers of CO ad- SAM-testbed is utilized to collect analog QMS data 2 sorbed on Rocknest materials. that can be used to interpret SAM-QMS data. The JSC Peak 4 CO release occurs at tempertures that are SAM-testbed operates at 30 mb He with a 3 ml min-1 2 consistent with the thermal decomposition of siderite flow rate. Calcite (Chihuahua, Mexico), magnesite (Fig. 2). A siderite composition of Fe Mg CO , sug- (Winchester, WI) and siderite (Fe Mg CO ) (Cop- 0.5 0.5 3 0.65 0.35 3 gests that at least 0.8 wt.% siderite may be present in per Lake Nova Scotia, Canada) were evaluated for the Rocknest material. CO release from magnesite comparison to CO release temperatures detected by 2 2 decomposition overlaps the peak 4 release but peaks at the SAM-QMS on Mars temperatures higher than siderite. Nevertheless, mag- nesite is still being considered a possibility and more shown to have at least a 100˚C lower decomposition work is needed to verify its presence. Calcite (not temperature relative to 2 to 50 µm sized calcite parti- shown) decomposition begins at 685˚C which is where cles [4]. These results suggest that nanophase car- the Rocknest CO releases are almost finished. This bonates may explain part of the contribution to the 2 suggests that coarse grained calcite is not a likely can- peak 2 and 3 CO releases. 2 didate for Rocknest bedform material. Decomposition of other phases at peak 2 and 3 tem- Peaks 2 and 3 and possibly some of peak 4 have peratures with carbonate may lower carbonate decom- CO contributions from oxidation of organics that may position temperature in the Rocknest material. For ex- 2 be derived from the SAM instrument [7,8]. However ample, hydrated Mg-perchlorate releases HCl upon current estimates of SAM derived organics suggest that decomposition and can partially decompose carbonate, only ~0.03 % of total C detected can be derived from releasing CO at temperatures below normal carbonate 2 SAM [7]. decomposition temperatures [3]. While Mg-perchlorate is not the leading perchlorate candidate for Rocknest [12] the possibility exists that other phases yet to be 6 Siderite 4 Magnesite evaluated may be promoting lower temperature de- Rocknest 1 Rocknest 2 2 composition of carbonate. 2 Rocknest 3 Conclusions: Four CO releases from the Rocknest Rocknest 4 2 )rabm( debtset-M 10-82468 89105)spc( tsenkcoR mC(wpOtae.t%a2e kra) i ra4eml) a.wa dyOes ronebrl beyd e edpate aCtfrertOciaatc2el,tl diy(o p bnea yato tkSrfi Ab1pu)Me taae.nkd dPs otF2otee /nacMtnoiadmgl bc3sauo rsu(bt0rioco.0nen1as t oeoCsff AS 7 organic contamination. Meteroitic organics mixed in -CSJ 10-98 6 the Rocknest bedform could be present, but the peak 2 6 5 and 3 C concentration (~0.21 C wt. %) is likely too 4 high to be attributed solely to meteoritic organic C. 4 2 Other inorganic sources of C such as interactions of 3 perchlorates and carbonates and sources yet to be 10-10 identified will be evaluated to account for CO re- 0 100 200 300 400 500 600 700 2 Temperature (°C) leased from the thermal decomposition of Rocknest Fig. 2. Rocknest CO2 releases (mass 45) versus temperture material. along with siderite and magnestite decomposition CO2 re- References: leases as determined by the JSC-SAM-testbed. [1] Boynton et al. (2009) Science, 325, 61. [2] Sutter et al. (2012) Icarus, 218, 290. [3] Cannon et al. (2012) Some of the C derived from peaks 2 and 3 could be GRL 39, L13203. [4] Lauer et al. (2012) LPS XLIII, derived from organic carbon in the Mars soil. Total C #2299. [5] Edgett et al. (2013) LPS XLIV. [6] Archer et in Mars surface materiasls derived from meteoritic (CI) al. (2013) LPS XLIV. [7] Glavin et al. (2013) LPS influx is estimated to be 0.03 to 0.10 wt.% C [9] which XLIV. [8] Eignebrode et al. (2013) LPS XLIV. [9] Yen suggests that up to 0.05 wt.% C may occur as organic et al. (2006) JGR, 111, E12S11. [10] Grady and C in Mars surface material [e.g., 10]. The 0.025 wt.% Wright, (2003) Space Sci. Rev. 106, 231. [11] Archer C concentration is considered an upper limit for mete- P. D. Jr. et al. (2012) Planet. Sci., submitted. [12] Sut- oritic dervived organics and is likely lower due Mars ter et al. (2013) LPS XLIV. surface chemical processes that may oxidize surface organic carbon. This indicates that other sources of inorganic carbon likely exist to account for the 0.06 wt.% C in peaks 2 and 3 Smaller particle sized carbonates are a potential source of the lower temperature CO releases. Recent 2 work [4,11] has demonstrated that calcite particle size has an effect on calcite decomposition temperatures. Calcite particles in the 2-50 µm range have a 20˚C lower decomposition temperature than 250 µm size calcite particles. This temperature drop may not ex- plain the ~90˚C difference between peaks 3 and 4. However, proposed nanophase carbonates have been