The Chemical Composition of Martian Soil and Rocks Returned by the Mobile Alpha Proton X-ray Spectrometer: Preliminary Results from the X-ray Mode

Rieder, R.; Economou, T.; Wänke, H.; Turkevich, A.; Crisp, J. A.; Brückner, J.; Dreibus, G.; McSween, H. Y.

doi:10.1126/science.278.5344.1771

Cited by 550 publications

(310 citation statements)

References 12 publications

(13 reference statements)

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“…Although calibrations are still being refined, published APXS data for the rocks analyzed at the Pathfinder site showed enrichments in silica within the range of-50.0-65.0% by weight [Rieder et al, 1997]. This yields an average igneous composition equivalent to andesite.…”

Section: Composition Of Rocks and Soils At The Pathfinder Sitementioning

confidence: 99%

Exploring for a record of ancient Martian life

Farmer¹,

Marais²

1999

J. Geophys. Res.

296

222

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Abstract. The immediate task facing exopaleontology is to define a strategy to explore Mars for a fossil record during the decade-long exploration program that lies ahead. Consideration of the quality of paleontological information preserved under different geological conditions is important if we are to develop a strategy with broad applicability. The preservation of microbial fossils is strongly influenced by the physical, chemical, and biological factors of the environment which, acting together, determine the types of information that will be captured and retained in the rock record. In detrital sedimentary systems, preservation is favored by rapid burial in fine-grained, clay-rich sediments. In chemical sedimentary systems, preservation is enhanced by rapid entombment in finegrained chemical precipitates. For long-term preservation, host rocks must be composed of stable minerals that are resistant to chemical weathering and that form an impermeable matrix and closed chemical system to protect biosignatures from alteration during subsequent diagenesis or metamorphism. In this context, host rocks composed of highly ordered, chemically stable mineral phases, like silica (e.g., cherts) or phosphate (e.g., phosphorites), are especially favored. Such lithologies tend to have very long crustal residence times and, along with carbonates and shales, are the most common host rocks for the Precambrian microfossil record on Earth. Although we make the defensible assumption that Mars was more like the Earth early in its history, clearly, the geological and historical differences between the two planets are many. Such differences must be carefully considered when adapting an Earth-based strategy to Mars. IntroductionThe present emphasis in Mars exploration lies in the search for a fossil record [Klein and Farmer, 1995]. On Earth the long-term preservation of fossils occurs under a fairly narrow range of geological conditions [Knoll, 1984; Allison and Briggs, 1991a; Allison and Pye, 1994]. Favored environments share many basic physical and compositional characteristics that serve to guide the search for a microbial fossil record, whether in ancient stratigraphic sequences on Earth or, with appropriate adaptation, on other planetary surfaces like Mars. Because the basic conceptual framework and methodology required for paleontological exploration of other planetary bodies differ substantially from the search for extant life (embraced by the traditional discipline of exobiology), we refer to the former activity as "exopaleontology" [Farmer, 1995].In this paper we seek to create a historical perspective about the Earth's biosphere that will serve as a practical context for Mars exploration. The early history of the terrestrial biosphere and the factors that control life's limits are important constraints for assessing the probability that Mars developed life. Such constraints also provide a focus for the identification of potential habitable zones (past or present) on Mars.At the heart our strategy for Mars exopaleontology ...

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Section: Composition Of Rocks and Soils At The Pathfinder Sitementioning

confidence: 99%

Exploring for a record of ancient Martian life

Farmer¹,

Marais²

1999

J. Geophys. Res.

296

222

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“…Nearly pure silica coatings are colorless, but weathered basaltic detritus incorporated into older coatings produces colors ranging from brown to red. Measured SiO 2 contents for these rinds are higher (>66 wt %, and commonly >80%) than that estimated for the Pathfinder sulfur-free rock, and analyzed oxide sums are lower (<90%, as appropriate for opal or hydrated silica glass) than some Pathfinder rocks (low sums in some APXS analyses are thought to result from variations in the measurement geometry [Rieder et al, 1997a] (Table 3), which would presumably be represented in a volcanic rock by pigeonite and augite, respectively. Adams et al [1986] found that the best spectral match for rocks at the Viking 1 Lander site was a mixture of gray andesite with palagonite dust and a coarse rock-like soil.…”

Section: Rock Norm and Classificationmentioning

confidence: 99%

“…Impact melting of terrestrial loess produces glassy, vesicular rocks of variable composition which have spectra similar to Pathfinder rocks. However, the compositions of soils at the Pathfinder site [Rieder et al, 1997a] are distinct from the sulfur-free rock composition, so fractionation during shock melting would be required.…”

Section: Rock Norm and Classificationmentioning

confidence: 99%

“…Like the rocks, the Pathfinder soils [Rieder et al, 1997a] are normalized to 98% total oxides. For comparison purposes, XRF analyses of Viking soils [Clark et al, 1982] have been normalized to 95.4% total oxides (98% minus the average Pattffmder soil value of Na20 + K20 = 2.6%, oxides which were below detection limits in the Viking data set).…”

Section: The Total Energy Deviation For a Particular Energy Was Less mentioning

confidence: 99%

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Chemical, multispectral, and textural constraints on the composition and origin of rocks at the Mars Pathfinder landing site

McSween¹,

Murchie²,

Crisp³

et al. 1999

J. Geophys. Res.

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232

166

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Abstract. Rocks at the Mars Pathfinder site are probably locally derived. Textures on rock surfaces may indicate volcanic, sedimentary, or impact-generated rocks, but aeolian abration and dust coatings prevent unambiguous interpretation. Multispectral imaging has resolved four spectral classes of rocks: gray and red, which occur on different surfaces of the same rocks; pink, which is probably soil crusts; and maroon, which occurs as large boulders, mostly in the far field. Rocks are assigned to two spectral trends based on the position of peak reflectance: the primary spectral trend contains gray, red, and pink rocks; maroon rocks constitute the secondary spectral trend. The spatial pattern of spectral variations observed is oriented along the prevailing wind direction. The primary spectral trend arises from thin ferric coatings of aeolian dust on darker rocks. The secondary spectral trend is apparently due to coating by a different mineral, probably maghemite or ferrihydrite. A chronology based on rock spectra suggests that rounded maroon boulders constitute the oldest petrologic unit (a flood deposit), succeeded by smaller cobbles possibly deposited by impact, and followed by aeolian erosion and deposition. Nearly linear chemical trends in alpha proton X-ray spectrometer rock compositions are interpreted as mixing lines between rock and adhering dust, a conclusion supported by a correlation between sulfur abundance and red/blue spectral ratio. Extrapolations of regression lines to zero sulfur give the composition of a presumed igneous rock. The chemistry and normative mineralogy of the sulfurfree rock resemble common terrestrial volcanic rocks, and its classification corresponds to andesite. Igneous rocks of this composition my occur with clastic sedimentary rocks or impact melts and breccias. However, the spectral mottling expected on conglomerates or breccias is not observed in any APXS-analyzed rocks. Interpretation of the rocks as andesites is complicated by absence of a "1 gm" pyroxene absorption band. Plausible explanations include impact glass, band masking by magnetite, or presence of calcium-and iron-rich pyroxenes and olivine which push the absorption band minimum past the imager's spectral range. The inferred andesitic composition is most sinfilar to terrestrial anorogenic icelandites, formed by fractionation of tholeiitic basaltic magmas. Early melting of a relatively primitive Martian mantle could produce an appropriate parent magma, supporting the ancient age of Patlff•nder rocks inferred from their incorporation in Hesperian flood deposits. Although rocks of andesitic composition at the Patlff•nder site may represent samples of ancient Martian crust, inferences drawn about a necessary role for water or plate tectonics in their petrogenesis are probably unwarranted.

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“…Both the Raman and infrared spectrometers can provide complementary mineralogical data -data that has yet to be obtained from any previous Mars mission. Furthermore, a laser plasma spectrometer (LPS) can also be integrated into the same optical chain to provide rapid elementary composition data on samples (much more rapidly yseconds to minutes compared with the 8-10 h required for the alphaproton-X-ray spectrometer (APXS) which is being adopted for the Mars Exploration Rovers) (Reider et al 1997;Castle et al 1998;Bertrand et al 2002;Bertrand R. 2002 private communication). The LPS/Raman has a passive front-end linking the optical outlet/inlet for both laser-based plasma generation and collection of spectral light with the actual instrument and laser pump electronics by an optical fibre.…”

Section: Gestation and Birth Of A Robotic Astrobiology Mission Proposmentioning

confidence: 99%

Astrobiological instrumentation for Mars – the only way is down

Ellery¹,

Kolb²,

Lämmer³

et al. 2002

International Journal of Astrobiology

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: In this paper, in this edition of the Journal commemorating the life and work of David Wynn-Williams, we consider approaches to the astrobiological investigation of Mars. We provide a brief account of the scientific rationale behind the approach presented here. In particular, we outline the capabilities of the Raman spectrometer for the detection of biomarkers. David Wynn-Williams was an active champion of this instrument who was keen to field-qualify a version in Antarctica with a view to flying a Raman instrument onboard a Mars-bound space mission. We examine a scenario for the deployment of such an instrument in conjunction with other instrumentation and argue that subsurface deployment of scientific instruments is essential if we are to succeed in detecting any evidence that may exist for former life on Mars. We outline a mission scenario -Vanguard -which represents a novel but low-risk, low-cost approach to Mars exploration that was conceived and developed jointly by one of the authors (Ellery) and the late David Wynn-Williams.

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The Chemical Composition of Martian Soil and Rocks Returned by the Mobile Alpha Proton X-ray Spectrometer: Preliminary Results from the X-ray Mode

Cited by 550 publications

References 12 publications

Exploring for a record of ancient Martian life

Exploring for a record of ancient Martian life

Chemical, multispectral, and textural constraints on the composition and origin of rocks at the Mars Pathfinder landing site

Astrobiological instrumentation for Mars – the only way is down

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