The Martian Surface Composition

Bibring, Jean‐Pierre; Érard, S.

doi:10.1007/978-94-017-1035-0_10

Cited by 14 publications

(12 citation statements)

References 44 publications

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“…The basaltic and andesitic-like signatures dominate the surface of Mars with only relatively minor olivine-rich or haematite-rich areas. However, Hamilton et al (2000Hamilton et al ( , 2003 and Bibring & Erard (2001) noted that the basaltic TES spectra do not closely match those of the shergottites. Furthermore, Wyatt & McSween (2002) and Wyatt et al (2004) modified the deconvolution mineralogy, significantly decreasing the estimated feldspar in both terrane types.…”

Section: Source Regions and The Martian Surfacementioning

confidence: 99%

The SNC meteorites: basaltic igneous processes on Mars

Bridges

Warren²

2006

JGS

135

128

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A group of 32 meteorites, the SNC (Shergotty, Nakhla, Chassigny) group, was derived from Mars as a product of 4-7 ejection events, probably from Tharsis and Elysium-Amazonis. The SNCs either have basaltic mineralogy or some are ultramafic cumulates crystallized from basaltic melts. The SNCs can be classified both petrographically and geochemically. We classify the shergottite SNC meteorites on the basis of their light rare earth element (LREE) depletion into highly depleted, moderately depleted and slightly depleted. The slightly depleted samples (which are mainly but not exclusively aphyric basalts) show high log 10 f O 2 values (QFM À1.0, where QFM is quartz-fayalite-magnetite). Highly depleted samples, which are mainly olivine-phyric basalts, have low log 10 f O 2 values (QFM À3.5). On the basis of mixing calculations between La/Lu and 87 Sr/ 86 Sr we favour models linking the correlation between LREE abundances and log 10 f O 2 to mantle heterogeneity rather than contamination by oxidized, LREE-rich crustal fluids. SNC chemistry in general reflects the Fe-rich mantle of Mars (which contains twice as much FeO as the Earth's mantle), the late accretion of chondritic material into the mantle, and possibly the presence of a plagioclaserich magma ocean, which acted to variably deplete the mantle in Al. The high FeO contents of the SNC melts are associated with high melt densities (allowing the ponding of large magma bodies) and low viscosities, both of which are consistent with the large scale of many observed martian lava flows.Of the approximately 30 000 currently known meteorites, 32 originated on Mars. The martian meteorites are also called the SNC group after three of its members: Shergotty, Nakhla, Chassigny. They are known to form a distinct group of meteorites from a single parent body on the basis of their relatively differentiated mineralogy and chemical compositions; oxygen isotope compositions that are related to each other by mass fractionation (e.g. Clayton & Mayeda 1996); high oxidation state for meteorites (log f O 2 between QFM (quartz-fayalite-magnetite) and IW (iron-wüstite); e.g. Herd 2003) and notably large range of crystallization ages (165 Ma to 4.5 Ga; Nyquist et al. 2001a).It is the crystallization ages that first led to wide acceptance that this meteorite group was derived from a large, slowly cooled planet, Mars (e.g. McSween et al. 1979;Wood & Ashwal 1981). However, suggestions that some meteorites might be derived from Mars can be traced back further (e.g. Wänke 1968). Papanastassiou & Wasserburg (1974) noted that one of the SNC meteorites (Nakhla) must have been derived from an (unspecified) planetary object with some affinities to the Earth that had undergone differentiation after 3.6 Ga. The definitive link to Mars was made through comparing the composition of gases within the shock-melted glass of shergottites with the composition of the martian atmosphere determined by the Viking landers (Bogard & Johnson 1983).The SNCs have a range of basaltic and ultramafic mineral as...

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Section: Source Regions and The Martian Surfacementioning

confidence: 99%

The SNC meteorites: basaltic igneous processes on Mars

Bridges

Warren²

2006

JGS

135

128

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“…Although from the morphologies of the flows and most of the volcanoes basaltic compositions are inferred to be dominant, remote sensing data from orbit and measurements made on the surface by Mars Pathfinder suggest that slightly more evolved magmas might also have been present in the evolution of the surface (see discussion in Bibring and Erard, 2001).…”

Section: Volcanismmentioning

confidence: 99%

Geological Processes and Evolution

Head

Greeley

Golombek

et al. 2001

Space Sciences Series of ISSI

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Abstract. Geological mapping and establishment of stratigraphic relationships provides an overview of geological processes operating on Mars and how they have varied in time and space. Impact craters and basins shaped the crust in earliest history and as their importance declined, evidence of extensive regional volcanism emerged during the Late Noachian. Regional volcanism characterized the Early Hesperian and subsequent to that time, volcanism was largely centered at Tharsis and Elysium, continuing until the recent geological past. The Tharsis region appears to have been largely constructed by the Late Noachian, and represents a series of tectonic and volcanic centers. Globally distributed structural features representing contraction characterize the middle Hesperian. Water-related processes involve the formation of valley networks in the Late Noachian and into the Hesperian, an ice sheet at the south pole in the middle Hesperian, and outflow channels and possible standing bodies of water in the northern lowlands in the Late Hesperian and into the Amazonian. A significant part of the present water budget occurs in the present geologically young polar layered terrains. In order to establish more firmly rates of processes, we stress the need to improve the calibration of the absolute timescale, which today is based on crater count systems with substantial uncertainties, along with a sampling of rocks of unknown provenance. Sample return from carefully chosen stratigraphic units could calibrate the existing timescale and vastly improve our knowledge of Martian evolution.

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“…Thermal emission spectrometry (e.g. at the Pathfinder site) also shows the basaltic nature of the dust and rocks (Bibring and Erard, 2001). In addition, the characteristic ferric absorption edge at 445−800 nm of the martian surface suggests the presence of palagonite i.e.…”

Section: Relationship Of Snc Secondary Assemblages To Current Martianmentioning

confidence: 99%

Untitled

Bridges

Catling

Saxton

et al. 2001

Space Science Reviews

215

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Abstract. The SNC (Shergotty-Nakhla-Chassigny) meteorites have recorded interactions between martian crustal fluids and the parent igneous rocks. The resultant secondary minerals -which comprise up to ~ 1 vol.% of the meteorites -provide information about the timing and nature of hydrous activity and atmospheric processes on Mars. We suggest that the most plausible models for secondary mineral formation involve the evaporation of low temperature (25-150 o C) brines. This is consistent with the simple mineralogy of these assemblages -Fe-Mg-Ca carbonates, anhydrite, gypsum, halite, clays -and the chemical fractionation of Ca-to Mg-rich carbonate in ALH84001 'rosettes'. Longer-lived, and higher temperature, hydrothermal systems would have caused more silicate alteration than is seen and probably more complex mineral assemblages. Experimental and phase equilibria data on carbonate compositions similar to those present in the SNCs imply low temperatures of formation with cooling taking place over a short period of time (e.g. days). The ALH84001 carbonate also probably shows the effects of partial vapourisation and dehydration related to an impact event postdating the initial precipitation. This shock event may have led to the formation of sulphide and some magnetite in the Fe-rich outer parts of the rosettes.Radiometric dating (K-Ar, Rb-Sr) of the secondary mineral assemblages in one of the nakhlites (Lafayette) suggests that they formed between 0 and 670 Ma, and certainly long after the crystallisation of the host igneous rocks. Crystallisation of ALH84001 carbonate took place 0.5 Ga after the parent rock. These age ranges and the other research on these assemblages suggest that environmental conditions conducive to near-surface liquid water have been present on Mars periodically over the last ~1 Ga. This fluid activity cannot have been continuous over geological time because in that case much more silicate alteration would have taken place in the meteorite parent rocks and the soluble salts would probably not have been preserved.The secondary minerals could have been precipitated from brines with seawater-like composition, high bicarbonate contents and a weakly acidic nature. The co-existence of siderite (Fe-carbonate) and clays in the nakhlites suggests that the pCO 2 level in equilibrium with the parent brine may have been 50 mbar or more. The brines could have originated as flood waters which percolated through the top few hundred metres of the crust, releasing cations from the surrounding parent rocks. There is no spectroscopic or photographic evidence for extensive evaporite deposits on the current martian surface but some salt precipitation through solute concentration must have occurred as floodwaters associated with many of the martian channels ponded in low-lying areas. The high sulphur and chlorine concentrations of the martian soil have most likely resulted from aeolian redistribution of such aqueously-deposited salts and from reaction of the martian surface with volcanic acid volatiles. However, the SNC...

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The Martian Surface Composition

Cited by 14 publications

References 44 publications

The SNC meteorites: basaltic igneous processes on Mars

The SNC meteorites: basaltic igneous processes on Mars

Geological Processes and Evolution

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