Submitted Manuscript: Confidential 7 November 2013
Volatile and Organic Compositions of Sedimentary Rocks in
Yellowknife Bay, Gale crater, Mars
D. W. Ming
1,*
, P. D. Archer, Jr.
2
, D. P. Glavin
3
, J. L. Eigenbrode
3
, H. B. Franz
3,4
, B.
Sutter
2
, A. E. Brunner
3,5
, J. C. Stern
3
, C. Freissinet
3,6
, A. C. McAdam
3
, P. R. Mahaffy
3
,
M. Cabane
7
, P. Coll
8
, J. L. Campbell
9
, S. K. Atreya
10
, P. B. Niles
1
, J. F. Bell III
11
,
D. L.
Bish
12
, W. B. Brinckerhoff
3
, A. Buch
13
, P. G. Conrad
3
, D. J. Des Marais
14
, B. L.
Ehlmann
15,16
, A. G. Fairén
17
, K. Farley
15
, G. J. Flesch
16
, P. Francois
8
, R. Gellert
9
, J. A.
Grant
18
, J. P. Grotzinger
15
, S. Gupta
19
, K. E. Herkenhoff
20
, J. A. Hurowitz
21
, L. A.
Leshin
22
, K. W. Lewis
23
, S. M. McLennan
21
, K. E. Miller
24
, J. Moersch
25
, R. V. Morris
1
,
R. Navarro-González
26
, A. A. Pavlov
3
, G. M. Perrett
9
, I. Pradler
9
, S. W. Squyres
17
, R. E.
Summons
24
, A. Steele
27
, E. M. Stolper
15
, D. Y. Sumner
28
, C. Szopa
8
, S. Teinturier
8
, M. G.
Trainer
3
, A. H. Treiman
29
, D. T. Vaniman
30
, A. R. Vasavada
16
, C. R. Webster
16
, J. J.
Wray
31
, R. A. Yingst
30
and the MSL Science Team
§
.
Affiliations:
1
Astromaterials Research and Exploration Science Directorate, NASA Johnson Space
Center, Houston, TX 77058, USA.
2
Jacobs, Houston, TX 77058, USA.
3
Planetary Environments Laboratory, NASA Goddard Space Flight Center, Greenbelt
MD 20771, USA.
4
Center for Research and Exploration in Space Science and Technology, University of
Maryland Baltimore County, Baltimore, MD 21250, USA.
5
Center for Research and Exploration in Space Science and Technology, Department of
Astronomy, University of Maryland, College Park, MD 20742, USA.
6
NASA Postdoctoral Program, NASA Goddard Space Flight Center, Greenbelt MD
20771, USA.
7
LATMOS, UPMC Univ. Paris 06, Université Versailles St-Quentin, UMR CNRS 8970,
75005 Paris, France.
8
LISA, Univ. Paris-Est Créteil, Univ. Paris Diderot & CNRS, 94000 Créteil, France.
9
Department of Physics, University of Guelph, Guelph, Ontario, Canada N1G2W1.
10
Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann
Arbor, MI 48109-2143, USA.
11
School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287,
USA.
12
Department of Geological Sciences, Indiana University, Bloomington, IN 47405, USA.
13
LGPM, Ecole Centrale Paris, 92295 Chatenay-Malabry, France.
Ming et al., Volatile and Organic Compositions of Sedimentary Rocks on Mars
2
14
Department of Space Sciences, NASA Ames Research Center, Moffett Field, CA
94035, USA.
15
Division of Geologic and Planetary Sciences, California Institute of Technology,
Pasadena, CA, 91125, USA.
16
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109,
USA.
17
Department of Astronomy, Cornell University, Ithaca, NY 14853, USA.
18
Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian
Institution, Washington, DC 20560, USA
19
Department of Earth Science and Engineering, Imperial College London, London, SW7
2AZ, UK.
20
U.S. Geological Survey, Flagstaff, AZ 86001, USA.
21
Department of Geosciences, State University of New York State at Stony Brook, NY
11794-2100, USA.
22
Department of Earth & Environmental Science and School of Science, Rensselaer
Polytechnic Institute, Troy, NY 12180, USA.
23
Princeton University, Princeton, NJ 08544, USA.
24
Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of
Technology, Cambridge, MA 02139, USA.
25
Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN
37996, USA.
26
Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Ciudad
Universitaria, México D.F. 04510, Mexico.
27
Geophysical Laboratory, Carnegie Institution of Washington, Washington DC 20015,
USA.
28
Department of Earth and Planetary Sciences, University of California, Davis, CA
95616, USA.
29
Lunar and Planetary Institute, Houston, TX 77058, USA.
30
Planetary Science Institute, Tucson, AZ 85719, USA.
31
School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta,
GA 30332, USA.
*Corresponding to: douglas.w.ming@nasa.gov
§
MSL Science Team authors and affiliations are listed in the supplementary materials.
Abstract: H
2
O, CO
2
, SO
2
, O
2
, H
2
, H
2
S, HCl, chlorinated hydrocarbons, NO and other
trace gases were evolved during pyrolysis of two mudstone samples acquired by the
Curiosity rover at Yellowknife Bay within Gale crater, Mars. H
2
O/OH-bearing phases
included 2:1 phyllosilicate(s), bassanite, akaganeite, and amorphous materials. Thermal
Ming et al., Volatile and Organic Compositions of Sedimentary Rocks on Mars
3
decomposition of carbonates and combustion of organic materials are candidate sources
for the CO
2
. Concurrent evolution of O
2
and chlorinated hydrocarbons suggest the
presence of oxychlorine phase(s). Sulfides are likely sources for S-bearing species.
Higher abundances of chlorinated hydrocarbons in the mudstone compared with
Rocknest windblown materials previously analyzed by Curiosity suggest that indigenous
martian or meteoritic organic C sources may be preserved in the mudstone; however, the
C source for the chlorinated hydrocarbons is not definitively of martian origin.
Introduction: Curiosity landed in Gale crater on August 6, 2012 (UTC) with a goal to
explore and quantitatively assess a site on Mars’ surface as a potential habitat for past or
present life. A topographic low informally named Yellowknife Bay located about 0.5 km
northeast of the landing site was chosen as the first major exploration target because
strata exposed were inferred to be fluvio-lacustrine deposits (1). Fluvio-lacustrine
depositional systems are thought to preserve measurable evidence of paleo-habitability
(2), e.g., factors such as mineral associations, elemental inventory, redox state, and
character of light elements and compounds.
Curiosity entered Yellowknife Bay on Sol 125 (December 12, 2012) and began a
drilling campaign to obtain powder samples from a mudstone located near the base of an
exposed stratal succession (3,4). Two drill samples informally named John Klein (drilled
on sol 183) and Cumberland (drilled on sol 279) were extracted for delivery to the
Sample Analysis at Mars (SAM) (5) and Chemistry and Mineralogy (CheMin) (6)
instruments. The samples were obtained from the lowermost stratigraphic unit in the
Yellowknife Bay formation, informally named the Sheepbed member (1). The Sheepbed
member and an overlying medium to coarse-grained sandstone, named the Gillespie Lake
member, appear to have a complex post-depositional aqueous history. Apparent low
matrix permeability in these units suggests that they were lithified during an early
diagenetic event followed by at least one additional aqueous episode when Ca-sulfate
minerals precipitated in a network of intersecting fractures (7). Millimeter-sized nodules
and hollow nodules in the Sheepbed member are interpreted, respectively, to be
concretions and void spaces possibly formed as trapped gas bubbles during early
diagenesis and lithification (1). The geology, stratigraphy, and diagenetic history of
Yellowknife Bay are described in detail in companion papers (1,7,8).
The John Klein (JK) and Cumberland (CB) targets were drilled about 3 meters
apart in the Sheepbed mudstone and within ≈10 cm of the same stratigraphic position.
The JK drill hole intersected thin Ca-sulfate-rich veins. The CB sample was collected
from an area rich in nodules and poor in Ca-sulfate-rich veins, to aid in mineralogical and
geochemical characterization of the nodules. Powders extracted from both holes were
gray in color suggesting a relatively unoxidized material (1,8), in contrast to the red-
colored, oxidized materials observed earlier by Curiosity at the Rocknest aeolian deposit
(9,10) and other surface soils (11) encountered by previous missions (12). Additional
details on the drill holes are described in (1) and (8), including maps of light-toned
fractures in the drill hole walls (8).
Here we describe the volatile and organic C content of the Sheepbed mudstone
and evaluate its potential for preservation of organic C. Volatile-bearing phases
Ming et al., Volatile and Organic Compositions of Sedimentary Rocks on Mars
4
(including possible organic material) in Sheepbed are indicators of its past environmental
and geochemical conditions and can shed light on whether the environment recorded in
this mudstone once was habitable, i.e., met the requirements for microbial life as known
on Earth (13). The volatile and organic compositions of JK and CB materials were
characterized by the SAM instrument’s evolved gas analysis (EGA), gas chromatography
mass spectrometry (GCMS), and tunable laser spectroscopy (TLS) experiments (14).
Four JK subsamples (JK-1, JK-2, JK-3, and JK-4) and four CB subsamples (CB-1, CB-2,
CB-3, and CB-5) of the <150 µm size fraction of drill fines were delivered to SAM for
EGA and GCMS analyses (15).
Evolved H
2
O. The most abundant gas evolved from JK and CB materials was H
2
O. H
2
O
abundances released from JK (1.8-2.4 wt. % H
2
O) and CB (1.7-2.5 wt. % H
2
O; Table 1)
were similar to Rocknest (1.6 – 2.4 wt. % H
2
O) (10). Other major evolved gases, in
descending order of abundance, were H
2
, CO
2
, SO
2
, and O
2
from JK and H
2
, O
2,
CO
2
, and
SO
2
from CB (Table 1, Figs. 1 and 2).
An independent estimate of the volatile inventory of JK and CB can be obtained
from measurements made by the Alpha Particle X-ray Spectrometer (APXS) (16). The
measurement calculates the bulk concentration of the aggregate of excess light elements
(including H
2
O, CO
2
, C, F, B
2
O
3
and Li
2
O) using the relative intensities of Compton- and
Rayleigh-scattering peaks (17,14). Estimates of the average excess light-element
concentrations for the JK drill tailings (APXS measurement on Sol 230) and the CB drill
tailings (Sol 287) were 4.3 (±5.5) and 6.9 (±6.2) wt. %, respectively. The two methods
for determining volatile abundances in the mudstone are consistent within uncertainties.
The JK and CB samples showed similar releases of H
2
O in EGA experiments
with a continuous temperature ramp (Figs. 1a, 2a) (18,19). Evolved H
2
O from JK (JK-4)
resulted in two major H
2
O releases, with very broad peaks at about 160 and 725°C (Fig.
1a). Cumberland samples exhibited similar behavior (Fig. 2a). The majority (~70%) of
H
2
O was driven off in the lower temperature peak.
CheMin results constrain the potential phases releasing H
2
O in the lower peak in
JK and CB samples. CheMin detected basaltic silicate minerals (feldspar, pyroxene,
olivine), magnetite (maghemite), anhydrite, bassanite, akaganeite, sulfides and
approximately 30 wt. % x-ray amorphous components in addition to a 2:1 trioctahedral
phyllosilicate in JK and CB (8). Therefore, candidates for the lower temperature water
release are H
2
O adsorbed on grain surfaces, interlayer H
2
O associated with exchangeable
cations in 2:1 phyllosilicates (e.g., smectite), structural H
2
O (e.g., bassanite), structural
OH (e.g., Fe-oxyhydroxides such as akaganeite), and occluded H
2
O in glass or minerals.
Adsorbed H
2
O and interlayer H
2
O in 2:1 phyllosilicates will generally release water
below 300 °C. Bassanite (CaSO
4
.
½H
2
O) dehydrates at ~150 °C. Akaganeite
(FeO(OH,Cl)) undergoes dehydroxylation at ~250 °C (Fig. S2). H
2
O incorporated into
the amorphous components (e.g., nanophase Fe-oxides, allophane/hisingerite) may also
evolve below 450 °C. Water as liquid or vapor inclusions in glass or minerals would be
released over a wide range of temperatures. Additional sources of evolved H
2
O at low
temperatures not constrained by CheMin include structural H
2
O in oxychlorine
compounds (e.g., hydrated perchlorates), structural OH in organics, and H
2
O formed
Ming et al., Volatile and Organic Compositions of Sedimentary Rocks on Mars
5
during organic reactions in the SAM pyrolysis oven. Organic matter can release H
2
O over
a wide range of temperatures from structural O and H as a consequence of reactions that
take place in the SAM oven.
The high-temperature H
2
O release between 450-835 °C is consistent with the
dehydroxylation of the octahedral layer of a 2:1 phyllosilicate (e.g., smectite), although
other phases that contain OH in octahedral layers may also evolve H
2
O in this
temperature region. The basal (001) spacing of the JK phyllosilicate measured by
CheMin was mostly collapsed to around 10 Å suggesting a 2:1 phyllosilicate with little
interlayer H
2
O (8). The 2:1 phyllosilicate in the CB sample was expanded, with a basal
(001) spacing of ~13-14 Å, consistent with several possible interpretations; the CB
phyllosilicate could be smectite with an interlayer partially occupied by metal-hydroxyl
groups or smectite with high hydration-energy cations (e.g., Mg
2+
) facilitating retention
of H
2
O (8). The high-temperature H
2
O releases at 750 °C can be ascribed to
dehydroxylation of Mg- and Al-enriched octahedral sheets in 2:1 phyllosilicates (Fig. 3a).
The most likely candidate for the high-temperature H
2
O release (i.e., ~750°C) in
Sheepbed material is saponite or Fe-saponite based upon CheMin measurement of the 02l
diffraction band (4.58 Å) as consistent with a trioctahedral 2:1 phyllosilicate (8) and the
water release peak temperature (Fig. 3a). If all of the H
2
O released between 450-835°C
during SAM pyrolysis runs resulted from dehydroxylation of 2:1 phyllosilicates, the
proportions of 2:1 phyllosilicate present in the JK and CB samples are 17 (±12) wt. %
and 16 (±11) wt. %, respectively. These values are consistent with the independent
estimates from CheMin XRD semi-quantitative data, which give 22 (±11) and 18 (±9) wt.
% for 2:1 phyllosilicate in JK and CB, respectively (8).
High-temperature release of H
2
occurs over roughly the same temperature regions
as the high-temperature releases of H
2
O and H
2
S (Figs. 1 & 2). The origin of the high
temperature evolved H
2
is unknown but is likely associated with the dehydroxylation of
the most thermally stable OH groups in the 2:1 phyllosilicates.
Evolved O
2
. The JK and CB samples have distinctly different O
2
releases (Figs. 1a and
2a; Table 1). The onset of O
2
evolution from JK (~150 °C) was lower than for CB (~230
°C). O
2
abundances released from CB (0.3-1.3 wt. % Cl
2
O
7
) were nearly 8 times greater
than JK (0.07-0.24 wt. % Cl
2
O
7
); Rocknest O
2
abundances (0.4 wt. % Cl
2
O
7
) were about
4 times greater than JK (Table 1). By comparison, the perchlorate anion (ClO
4
-
) was
present in soil at the Phoenix landing site at the 0.4 – 0.6 wt % level (20). The JK-4
sample had two distinct peaks, suggesting different or additional O
2
-evolving phases in
the JK sample or consumption of O
2
during combustion of organic materials (see below)
or thermal oxidation of ferrous-containing phases (e.g., magnetite to maghemite
transition). O
2
evolution in the Rocknest aeolian material occurred at a higher
temperature (onset ~300 °C with a peak temperature ~400 °C) than JK and CB (10,21).
Evolved O
2
from JK and CB is inferred to result from decomposition of
perchlorate or chlorate salts, based on analogy with other analyses on Mars, bulk
compositions of the JK and CB samples, on the timing of chlorinated hydrocarbon and
HCl releases, and on laboratory experiments with perchlorate salts. Perchlorate was
definitively identified in soil at the Mars Phoenix landing site (20), and O
2
release from
![Fig. 2. Evolved gas analysis for a continuous ramp SAM pyrolysis of drill material (<150 µm) from the Sheepbed mudstone Cumberland 2 (CB-2) sample: A) Mostabundant evolved gases [CO2 and SO2 counts have been scaled up 3 and 15 times, respectively]. B) Evolved gas traces for H2, H2S, HCl, CH3Cl, and CH2Cl2 [H2S and HCl traces have been scaled up 35 times; CH3Cl and CH2Cl2 have been scaled up 100 and 300 times, respectively]. Isotopologues were used to estimate species that saturated the QMS detector (m/z 12 for CO2 and m/z 20 for H2O).](/figures/fig-2-evolved-gas-analysis-for-a-continuous-ramp-sam-2psanyg8.webp)
![Fig. 3. Major evolved gases from the John Klein (JK) and Cumberland (CB) samples compared with EGA of analog minerals under SAM-like oven operating conditions (14). A) Evolved H2O for nontronite, montmorillonite, and saponite compared with JK and CB evolved H2O. B) Evolved O2, SO2, HCl, and H2S for CB-2 compared with pyrrhotite mixed with a Ca-perchlorate run under SAM-like operating conditions in laboratory experiments [Note HCl evolution coinciding with O2 release for CB-2 and laboratory pyrrhotite/perchlorate experiments]. C) Evolved O2 for several perchlorate salts compared with John Klein and Cumberland evolved O2.](/figures/fig-3-major-evolved-gases-from-the-john-klein-jk-and-30smzvma.webp)
![Fig. 1. Evolved gas analysis for a continuous ramp SAM pyrolysis of drill material (<150 µm) from the Sheepbed mudstone John Klein 4 (JK-4) sample: A) Most-abundant evolved gases [CO2 has been scaled up 3 times; SO2 and O2 have been scaled up 10 times]. B) Evolved gas traces for H2, H2S, HCl, CH3Cl, and CH2Cl2 [H2S and HCl traces have been scaled up 35 times; CH3Cl, and CH2Cl2 have been scaled up 100x]. Isotopologues were used to estimate species that saturated the QMS detector (m/z 12 for CO2 and m/z 20 for H2O).](/figures/fig-1-evolved-gas-analysis-for-a-continuous-ramp-sam-2fvgsjvp.webp)