Hyperfine Interact (2008) 186:173–180 DOI 10.1007/s10751-008-9850-2
Weathering of Martian and Earth surface studied by Mössbauer spectroscopy A. Wojnarowska · J. Gałazka-Friedman ˛ · N. Bakun-Czubarow
Published online: 22 October 2008 © Springer Science + Business Media B.V. 2008
Abstract Martian regolith and Earth’s basaltoid samples have been investigated by means of Mössbauer spectroscopy. The identification of the same minerals: olivine, pyroxene, magnetite, hematite and confrontation of the Fe3+ /Fe2+ , Fe3+ /Fetot , Fe2+ /Fetot ratios are presented. Co-existence of olivine and hematite in Martian regolith, absent in presented by authors terrestrial samples has been tentatively explained. Keywords Mössbauer spectroscopy · Martian regolith · Basaltoids
1 Introduction Based on orbital observations and the examination of the Martian meteorite, the surface of Mars appears to be composed primarily of basalt. Martian basaltic lava emerged on the planet’s surface and influenced its landscape. On the Earth’s surface, basaltoids are the most common volcanic rocks. Most likely, basaltoids and products of their alteration are main rocks on the surface of the other terrestrial planets in the Solar System [1–3] including Mars. Several sources can give information about composition of the Martian soil: spectroscopic measurements from Earth and various Mars orbiters, direct experiments performed during the Viking mission, simulations of Viking biology experiments and investigations of the SNC-meteorites. As a result of fitting the fluorescence spectra of terrestrial analogs to the fluorescence spectrum of the Martian soil, it has been
A. Wojnarowska (B) · J. Gałazka-Friedman ˛ Faculty of Physics, Warsaw University of Technology, 75 Koszykowa, 00-662 Warszawa, Poland e-mail:
[email protected] N. Bakun-Czubarow Institute of Geological Sciences, Polish Academy of Sciences, 51/55 Twarda, 00-818 Warszawa, Poland
174 Table 1 Fe3+ /Fe2+ , Fe2+ /Fetot and Fe3+ /Fetot ratios (estimated from MS) of samples from Spirit rover
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SOL rock name 82 Mazatzal Oregon 79 Mazatzal New York 83 Mazatzal Oregon ai 194 Sabre as is SOL soil name 429 Paso Robles 77 Mazatzal Flats 74 Bear Paw 69 Deserts Gobi
Fe3+ /Fe2+
Fe2+ /Fetot
Fe3+ /Fetot
0.28 ± 0.03
0.78 ± 0.04
0.22 ± 0.02
0.60 ± 0.05
0.62 ± 0.04
0.38 ± 0.02
0.89 ± 0.09
0.53 ± 0.06
0.47 ± 0.04
1.24 ± 1.11
0.45 ± 0.05
0.55 ± 0.05
0.12 ± 0.03 0.36 ± 0.04 0.41 ± 0.02 0.52 ± 0.02
0.90 ± 0.09 0.74 ± 0.06 0.71 ± 0.02 0.63 ± 0.03
0.10 ± 0.02 0.26 ± 0.03 0.29 ± 0.01 0.33 ± 0.02
Fig. 1 Mössbauer spectrum of Mazatzal rock (from Spirit rover)
concluded that the soil on the surface of Mars contains about 80% of an iron-rich clay, 10% of MgSO4 , 5% of iron oxides, and probably a little of CaCO3 . Since iron belongs to the major elements in the chemical composition of Martian soil, the problem of the identification of mafic minerals on the Mars surface can be resolved by means of Mössbauer spectroscopy. Investigations of soil on the surface of Mars by means of Mössbauer spectrometer and first descriptions of the prototypes of Martian Mössbauer spectrometer were suggested and published at the turn of 1980s of twentieth century [4–9].
2 Material and method Data from Mars were acquired by miniaturized spectrometer MIMOS II, which is a part of the Athena payload of NASA’s twin Mars Exploration Rovers (MER 2003) “Spirit” and “Opportunity” [10–12]. Those data are available for open public and were downloaded from MER Analyst’s Notebook website,
Mössbauer spectroscopic study of Martian and Earth surface Table 2 Fe3+ /Fe2+ , Fe2+ /Fetot and Fe3+ /Fetot ratios (estimated from MS) for the samples from Opportunity rover
Fe3+ /Fe2+ SOL rock name 67 Bounce Rock (RU) 29 McKittrick as is (RU) 105 Lion Stone as is (RU) 48 Moessberry (RU) SOL soil name 23 Hematit Slope (SU) 60 Mont Blanc Bright Soil 228 BerrySurvey (SU) 99 Leahs Choice (SU)
175 Fe2+ /Fetot
Fe3+ /Fetot
1.0 ± 0.1 1.25 ± 0.02
0.44 ± 0.02
0.56 ± 0.02
2.10 ± 0.09
0.32 ± 0.06
0.68 ± 0.04
4.21 ± 0.17
0.19 ± 0.03
0.81 ± 0.04
0.37 ± 0.03
0.60 ± 0.05
0.22 ± 0.04
0.68 ± 0.06
0.59 ± 0.04
0.41 ± 0.04
1.47 ± 0.09
0.40 ± 0.03
0.60 ± 0.05
1.69 ± 0.12
0.37 ± 0.02
0.63 ± 0.06
Table 3 Relative peak areas (A) for iron associated with specific iron bearing phases for Mazatzal rock (from Spirit rover) Phase
A (%)
Olivine Pyroxene Fe3+ Magnetite
50.4 28.7 5.9 6.5
Uncertainty ±2%
Table 4 Relative peak areas (A) for iron associated with specific iron bearing phases for the Berry Bowl rock (from Opportunity rover) Phase
A (%)
Pyroxene Fe3+ Hematite Hematite
19.2 17.2 39.5 24.1
Uncertainty ±2%
http://anserver1.eprsl.wustl.edu/ [13]. Data were converted into user-friendly form using MerView—for easy display of MER-acquired Mössbauer data. MerView program was made accessible by David Agresti. Backscatter spectra were transformed to peaks down which simplified analyses in Recoil application. Rocks from Mongolian basaltic lava fields and Silesian basaltoids were measured at room temperature using a constant acceleration spectrometer; a 57 Co source in rhodium matrix was used, the activity being 50 mCi.
176 Table 5 Fe3+ /Fe2+ , Fe2+ /Fetot and Fe3+ /Fetot ratios (estimated from MS) of Adrirondack rock
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Fe3+ /Fe2+
Fe2+ /Fetot
Fe3+ /Fetot
34 Adirondack rat (RR) 33 Adirondack brush (RB) 18 Adirondack as is (RU)
0.21 ± 0.03
0.78 ± 0.04
0.17 ± 0.03
0.23 ± 0.03
0.77 ± 0.04
0.17 ± 0.03
0.30 ± 0.04
0.74 ± 0.05
0.22 ± 0.03
Fig. 2 Mössbauer spectrum of Berry Bowl rock (Opportunity rover)
3 Results and discussion Up to now, on the mentioned website, there are about 100 accessible Mössbauer data files for soils and 170 files for rocks. To specify, the term “Martian soil” denotes any loose unconsolidated materials that can be distinguished from rocks, bedrock or strongly cohesive sediments [9]. In this work spectra from different areas and with different alteration index are presented and compared. Mössbauer investigations of chosen Martian samples reveal presence of Fe3+ doublet as well as of the following minerals: silicates (olivine, pyroxene), pyrite, ilmenite (Spirit), chromite and jarosite (Opportunity), magnetite, hematite, goethite. The Fe3+ /Fe2+ , Fe3+ /Fetot , Fe2+ /Fetot ratios being useful indicators of the degree of alteration of the iron-rich volcanic rocks were studied and compared. Various iron bearing minerals are characterized by different iron oxidation states. Alteration degrees for the Earth’s samples were estimated from the spectra peak areas and compared with the results obtained for samples from Spirit and Opportunity rovers. First we estimated uncertainty of peak areas which include uncertainty of measurement method and spectra fitting. Then uncertainty of complex value was projected. For Spirit rover samples Fe3+ /Fe2+ ratio vary from 0.28 to 1.24 and for unaltered rocks and from 0.12 to 0.52 for soils (Table 1). Mazatzal rock from Spirit rover is an example of weakly altered rock with 0.1 Fe3+ /Fe2+ ratio and unaltered minerals (Fig. 1). Olivine is the most significant mineral in that sample with over 50% of the whole rock iron content (Table 2). For Adirondack rock, measurements of three different samples were performed and oxidation ratios were compared (Table 3). On the surface (“as is” samples) rock material is more oxidized due to cleaning (brush and rat) of the outer layer and Fe3+ /Fe2+ ratio decreases.
0.55 7.91 2.81 5.1 20
1
2
Px, Pl, Ne, Ol, Mag 0.52 7.56 2.59 4.97 25
3
Px, Pl, Ne, Ol, Mag 0.65 7.98 3.14 4.84 35
4 Px, Pl, Ne, Ol, Anl, Mag 0.69 7.7 3.14 4.56 32
5 Px, Pl, Ne, Anl Mag 0.94 9.31 4.51 4.8 38
6 Px, Pl, Sm, Hem, Mag? 1.28 7.22 4.05 3.16 36
7 Px, Pl, Ne, Sm, Mag, Hem 2.34 8.47 5.94 2.53 15
8 Sm, Px, Pl, Ne?, Hem − 11.13 11.13 − 48
9
− 10.85 10.85 − 50
Sm, Hem, Anl
10 Sm, Hem, Qtz, Kfs, Kln, Ill − 11.41 11.41 − 77
b In
magnetic phases
Anl analcime; Hem hematite; Ill illite; Kfs K feldspar; Kln kaolinite; Mag magnetite; Ne nepheline; Ol olivine; Pl plagioclase; Px pyroxene; Sm smectite; Qtz quarts a Mineral description determined by means of X-ray diffractometry
Fe3+ /Fe2+ Fetot (%) Fe3+ (%) Fe2+ (%) Fe (%) b
Mineral compositiona
Sample no.
Table 6 Fe3+ /Fe2+ , Fe2+ /Fetot and Fe3+ /Fetot ratios of the Lower Silesian basaltoid samples
Mössbauer spectroscopic study of Martian and Earth surface 177
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Fig. 3 Mössbauer spectrum of unaltered basaltoid, sample 1
Fig. 4 Mössbauer spectrum of strongly weathered basaltoid, sample 10
For Opportunity rover samples, Fe3+ /Fe2+ ratio vary from 1.25 to 4.25 for rocks and from 0.37 to 1.69 for soils (Table 4). Examples of investigated spectra (Figs. 1 and 2) from both rovers with iron content estimated from peak areas are presented (Tables 2 and 5). Berry Bowl rock from Opportunity rover is characterized by intense hematite sextet. Over 60% of Fe in that sample concentrates in hematite phase. That is a sample of characteristic spherules which were probably formed in the presence of large volume of liquid water [14, 15]. As Earth’s rocks 10 samples of the Lower Silesian basaltoids (Zareba ˛ Górna near ´ Poland) with growing alteration degree have been investigated (Table 6). FigLuban, ures (Figs. 3 and 4) show Mössbauer spectra for the most extreme samples unaltered and weathered basaltoids. In analysed basaltoids, subspectra intensity of olivine and pyroxene (containing and Fe2+ ) decreases as weathering degree increases. Sample 1 (of unaltered basaltoid) shows subspectra of olivine and pyroxene. The last sample contains only ferric iron in smectite and hematite and do not demonstrate any presence of ferrous iron (Table 6).
Mössbauer spectroscopic study of Martian and Earth surface
179
Fig. 5 Mössbauer spectrum of basaltic sample (Mn2) from Khorgo volcano
Table 7 Relative peak areas (A) for iron associated with specific iron bearing phases Mn2 sample
Table 8 Relative peak areas (A) for iron associated with specific iron bearing phases of the Khorgo volcano basalts
Phase
A (%)
Olivine Pyroxene Fe3+ Ulvöspinel Chromite Chromite
38.4 ± 3.0 27.9 ± 2.4 10.7 ± 1.2 8.8 ± 1.2 8.0 ± 1.1 6,2 ± 1.1
Mn1 Mn2 Mn3
Fe3+ /Fe2+
Fe2+ /Fetot
Fe3+ /Fetot
0.12 ± 0.05 0.10 ± 0.05 0.25 ± 0.03
0.89 ± 0.05 0.91 ± 0.04 0.80 ± 0.04
0.11 ± 0.04 0.09 ± 0.06 0.20 ± 0.03
In the representative sample of the Mongolian basalts from the Khorgo volcano locality the following minerals: olivine, pyroxene, ulvöspinel, chromite (Fig. 5) were identified (Table 7). For three samples (Mn1, Mn2, Mn3) from above mentioned locality the Fe3+ /Fe2+ ratios have been estimated and compared (Table 8). High percentage content of olivine and pyroxene (Table 7) and low Fe3+ /Fe2+ index demonstrate that still lava hasn’t been strongly influenced by external environment factors such as liquid water and wind activity.
4 Conclusions There are similarities between Martian and Earth’s samples. Similar minerals have been identified: olivine, pyroxene, magnetite and hematite. Fe3+ /Fe2+ ratio in igneous lava rocks is as small as in selected Martian samples. That indicates that selected Martian samples are fresh volcanic material, which is not surprising as volcanoes on Mars were active up to recent geological past. On Mars surface
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weathering effect has been observed. Outer layers of rocks has higher Fe3+ /Fe2 ratio than inner parts. In Earth samples investigated by us presence of olivine and hematite in one sample has not been identified (Table 6 and Fig. 5). These minerals were not found together even in weathered basaltoids (Fig. 4). In our opinion presented samples might be applicable analogues due to similar volcanic origin. On one hand, the common presence of olivine and hematite in Martian regolith (detected within one Mössbauer sample by means of Mössbauer spectrometry) can be explained as mixture of secondary minerals originated due to the intense chemical alteration of basaltic rocks and of olivine from young dust originated in the distant soil sources— sign of the strong wind activity. On the other hand, olivine and hematite are located on opposite ends of the terrestrial mafic rocks weathering sequence, thus their coexistance in one sample is not probable. Acknowledgements The authors express their gratitude to Professor David G. Agresti for providing MerView computer program—for easy display of MER-acquired Mössbauer data. The manuscript preparation was supported by grant UPB from Rector of Warsaw University of Technology.
References 1. Bakun-Czubarow, N., Gałazka-Friedman, ˛ J., Suwalski, J., Szpila, K.: Weathering of the lower silesian basaltoids studied by Mössbauer spectroscopy. Arch. Miner. 49, 3 (1993) 2. Bakun, N., Czubarow, N.: Mineralogy and petrology of the terrestrial planets. In: Teisseyre, ´ R., Leliwa-Kopystynski, J., Lang, B. (eds.) Evolution of the Earth and Other Planetary Bodies, PWN, p. 335. Elsevier, Amsterdam (1992) 3. Kieffer, H., Jakosky, B. Snyder, C., Matthews, M. (eds.): Mars. University of Arizona Press, Tucson (1992) 4. Morris, R.V., Agresti, D.G., Shelfer, T.D., Wdowiak, T.J.: Mössbauer spectroscopy for mineralogical analysis on planetary surfaces. In: Proceedings, Pathfinder Sample Acquisition, Analysis, and Preservation Instrument Technology Workshop (Johnson Space Center, Houston, November (1988)) 5. Galazka-Friedman, J.: The investigation of the surface of terrestrial planets. Postepy Astronomii. 36, 233 (1988) 6. Knudsen, J.M., Morup, S., Gałazka-Friedman, ˛ J.: Mössbauer spectroscopy and the iron on Mars. Hyperfine Interact. 57, 2231 (1990) 7. Agresti, D.G., Morris, R.V., Wills, E.L., Shelfer, T.D., Pimperl, M.M., Shen, M.H., Clark, B.C., Ramsey, B.D.: Extraterrestrial Mössbauer spectrometry. Hyperfine Interact. 72, 283 (1992) ´ A., Witek, A.: In: Szegoe, K. (ed.) 8. Galazka-Friedman, J., Kotlicki, A., Slawska-Waniewska, Environmental Model of Mars, vol. 2. Pergamon, Oxford, UK (1991) 9. Kligelhöfer, G., et al.: Mössbauer backscattering spectrometer for mineralogical analysis of Mars surface. Hyperfine Interact. 71, 1449 (1992) 10. Morris, R.V., Klingelhöfer, G., Bernhard, B., Schröder, C., Rodinov, D.S.: Mineralogy at Gusev crater from the Mössbauer spectrometer on the spirit rover. Science 305, 833 (2004) 11. Morris, R.V., Klingelhöfer, G., Bernhard, B., Schröder, C., Rodinov, D.S.: Jarosite and hematite at meridiani planum from opportunity’s Mössbauer spectrometer. Science 306, 1740 (2004) 12. Klingelhöfer, G., Morris, R.V., De Souza, P.A. Jr., et al.: Two years of Mössbauer studies of the surface of Mars with Mimos II. Hyperfine Interact. 170, 169 (2006) 13. Agresti, D., Darby Dyar, M., Schafer, M.W.: MERView: a new computer program for easy display of MER-acquired Mössbauer data. LPS 37, 1517 (2005) 14. University of Mainz site. http://iacgu32.chemie.uni-mainz.de/mer.html. Accessed 15 June 2007 15. Webster, G., Brown, D.: In NASA website available via http://www.jpl.nasa.gov/releases/ 2004/88.cfm. Accessed 15 June 2007