Our analyses of sulfate minerals, analog sites, and Martian spectra and spectral images is focused on characterization of the Martian surface and in particular identification of aqueous processes there

Bishop, J. L.

Brown, A. J.

Dyar, M. D.

Lane, M. D.

Parente, M.

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NASA Ames Research Center 
SULFATES ON MARS AS MARKERS OF AQUEOUS PROCESSES: AN INTEGRATED MULTI- 
DISCIPLINARY STUDY O F  MINERALS, MARS ANALOG SITES AND RECENT MISSION DATA. 
J. L. Bishop’, M. D. Lane2, M. D. Dyar3, A. J. Brown’ and M. Parente’. ’SET1 Institute/NASA-Ames Research 
Center, 515 N. Whisman Rd., Mountain View, CA 94043, ’Planetary Science Institute, 1700 E. Fort Lowell Rd., 
Suite 106, Tucson, AZ 85719, 3Mount Holyoke College, 50 College St., South Hadley, MA 01075. 5Electrical 
Engineering, Stanford Univ., Stanford, CA 94305. (contact: jbishop@.arc.nasa.gov) 
Recent analyses by the Mars Exploration Rovers 
(MERs) at Meridiani Planum and Gusev crater and 
the OMEGA instrument on Mars Express have 
provided detailed information about the presence of 
sulfates on Mars. We are evaluating these recent 
mission data in an integrated multi-disciplinary study 
of visiblehear-infrared (VNIR), mid-IR and 
Mossbauer spectra of several sulfate minerals and 
sulfate-rich analog sites. 
Recent Results from Martian Missions: 
Measurements using the APXS on outcrop rocks at 
Meridiani Planum suggest the presence of greatly 
elevated S levels, even as much as 20-40% sulfate 
[I]. The Mossbauer instrument identified jarosite as 
one sulfate-bearing mineral present at Meridiani [Z], 
and geochemical modeling [l]  and spectral analyses 
[3,4] suggest that other sulfate minerals are present as 
well. Recent analyses of the Mini-Thermal Emission 
Spectrometer (Mini-TES) data include spectral 
models using a mixture of hydrous and anhydrous 
sulfates to reproduce spectra of these outcrop rocks at 
Meridiani [5]. The presence of jarosite at Meridiani 
implies a highly acidic (pH <3) formation 
environment [6] and the sedimentary character of the 
jarosite-bearing sulfur-rich outcrops there is 
consistent with aqueous processes. 
Diagnostic NIR absorptions of the sulfate 
minerals kieserite and gypsum have been identified in 
data from the OMEGA instrument in several 
locations on Mars [7,8,9]. The deposits range from 
small, light-toned outcrops in Valles Marineris to 
regional sulfate-rich layers in the Meridiani region. 
Sulfates here are attributed to aqueous alteration. The 
Compact Reconnaissance Imaging Spectrometer for 
Mars (CRISM) on board the Mars Reconnaissance 
Orbiter will evaluate these sulfate-bearing sites at 
even smaller spots sizes on the surface [lo], and may 
enable identification of specific sulfate minerals. 
An initial study of hydrated iron sulfates showed 
that some of these minerals can explain a number of 
the Mossbauer, mid-IR and VNIR spectral features 
observed for the global Martian soil [3]. Our 
continued analyses suggest that ferrous sulfates may 
account for the Miissbauer features attributed to 
olivine [ 1 13 and that the mid-IR features attributed to 
a combination of bound water and carbonate [ 12,131 
may be explained by hydrated iron sulfates. Spectral 
analyses including novel statistical modeling techniques 
are underway for detection of sulfates on Mars by 
OMEGA and CRISM, and for groundtruthing these 
VNIR hyperspectral datasets using MER results. Recent 
processing and calibration of MER Mossbauer data is 
enabling further analyses of that dataset as vell. 
Sulfate precipitation in acidic environments. The 
sulfate-rich rock outcrops observed in Meridiani Planum 
may have formed in an acidic environment similar to 
acid rock drainage environments on Earth [4]. Minerals 
such as jarosite, szomolnokite and rozenite form under 
acidic conditions. Others that contain fenihydrite and 
gypsum formed under more neutral conditions. Our 
results imply that (i) sulfate minerals formed in Martian 
soils via chemical weathering, perhaps over very long 
time periods, and (ii) sulfate minerals precipitated 
following aqueous oxidation of sulfides to form the 
outcrop rocks at Meridiani Planum. 
Solfataric alteration. Solfataric alteration may 
have played a role in sulfate mineralization on Mars. 
Fumaroles in the Kilauea caldera, HI, have created a 
solfataric bank on the south wall of the crater where 
Keanakakoi ash was deposited, forming a combination 
of jarosite and gypsum in a silica/clay matrix [14]. In 
addition, tephra altered near cinder cones in the 
Haleakala crater, Maui, contain alunite-jarosite in a 
silica/clay/iron oxide/oxyhydroxide matrix [ 151. 
Summary: Our analyses of sulfate minerals, analog 
sites, and Martian spectra and spectral images is focused 
on characterization of the Martian surface and in 
particular identification of aqueous processes there. 
References: [l] Rieder R. et al. (2004) Science, 
306, 1746. [2] Klingelhofer G. et al. (2004) Science, 
306, 1740. [3] Lane M. D. et al. (2004) GRL, 31. [4] 
Bishop J. L. et al. (2005) IJA, 3, 275. [5] Christensen P. 
R. et al. (2004) Science, 306, 1733. [6] Bigham J. M. et 
al. (1992) in Biornineralization Processes of Iron ..., 
Catena Verlag, p. 219. [7] Arvidson R. E. et al. (2005) 
Science, 307, 1591. [8] Bibring J.-P. et al. (2005) 
Science, 307, 1576. [9] Gendrin A. et ai. (2005) Science, 
307, 1587. [lo] Murchie S. et al. (2003) 6th Znf‘l ConJ 
Mars, CD-ROM #3062. [I 13 Morris R. V. et al. (2004) 
Science, 305, 833. [12] Bandfield J. L. et al. (2003) 
Science, 301, 1084. [13] Christensen P. R. et al. (2004) 
Science, 305, 837. [I41 Bishop J. L. et al. (2005) LPSC 
XKYVZ., CD-ROM #1456, [I51 Bishop J. L. et al. (2006) 
Acknowledgments: Support for this work from 
LPSC. X D T Z Z . ,  CD-ROM #1423. 
N - ~ S A ’ E  N.41 and MFI? prognm i3 much appriiiatd. 
https://ntrs.nasa.gov/search.jsp?R=20060051757 2019-08-30T00:04:49+00:00Z


Sulfates on Mars as Markers of Aqueous Processes: An Integrated Multidisciplinary Study of Minerals, Mars Analog sites and Recent Mission Data

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