Martian origin, meteorites

Induced TL properties have therefore enabled new insights into low-grade metamorphism and devitrification, shock, brecciation and the postulated Martian origin of certain meteorites and their components. 

Figure 3 Comparison of molecular and isotopic abundances of the Mars atmosphere (Viking measurements) with trapped gases in impact-melted glass in the EETA79001 shergottite. This correspondence is evidence of the meteorite s martian origin (after Treiman et al., 2000).

Of the >7500 different meteorites in scientific collections, a few are of Lunar or Martian origin (31 and 32, respectively) thousands of others come... 

Martian (SNC) meteorites, remote sensing, and spacecraft exploration have provided insights into the origin, evolution and interaction of several light-element reservoirs on Mars including the lithosphere, hydrosphere and atmosphere. Beyond Earth, Mars is certainly the most exhaustively investigated body from a stable isotopic perspective. 

A dog killed in Nakhla, Egypt, in 1911 is reported to be the only known casualty of a Martian meteorite. In 1984, a meteorite of Martian origin (ALH84001) was discovered in Antarctica and contained what looked like fossil bacteria. The evidence remains inconclusive and controversial. 

The Shergotty-Nakhla-Chassigny (SNC) meteorites are believed to be of Martian origin. They contain 0.04-0.4% water by weight. The question is whether this water is of terrestrial or extraterrestrial origin (Karlsson et al., 1991 [179]). Oxygen isotope measurements can be used to answer this question. A detailed analysis of water in SNC meteorites showed ... 

Origin. Typical meteorites have formation ages of 4.55 Gyr and exposure ages of only 10 years, duting which time they existed as meter-sized bodies unshielded to the effects of cosmic rays. With the exception of the SNC (Martian) and lunar meteorites it is widely befleved that most conventional... 

Becker L. et al. (1999). The origin of organic matter in the Martian meteorite ALH84001. 

Martian meteorites and Mars rover analyses suggest that it is a basalt-covered world, a conclusion supported by orbital measurements. Basalts of different ages appear to have distinct compositions. Since its original differentiation, the Martian mantle has remained geochemically isolated, although it is periodically melted to produce basalts. The core has an appreciable amount of sulfide, as inferred from trace elements in basalts. Water, once important in producing clays and sulfates, has now retreated into the subsurface. 

On the basis of their chemistry, a small number of meteorites are believed to have originated from Mars. Warren, Kallemeyn and Kyte (1999, 2107, 2114) had six suspected Martian meteorites analyzed for arsenic. Arsenic was listed as not detected in two of the samples (ALH77005 and Y-793605). Four others (ALH84001, EET70001, EET79001, and QUE94201) had <0.03 to <0.7 mg kg-1 of arsenic (Warren, Kallemeyn and Kyte, 1999 Table 3.2). Warren, Kallemeyn and Kyte (1999, 2107, 2114) also admit that the arsenic analyses were imprecise (within about 10%) and that they could have been influenced by terrestrial weathering. 

Warren, P.H., Kallemeyn, G.W. and Kyte, F.T. (1999) Origin of planetary cores evidence from highly siderophile elements in Martian meteorites. Geochimica et Cosmochimica Acta, 63(13-14), 2105-22. 

In terms of the original concentrations (Soln. A, Table 5.3), 0.0008 moles of Fe2+ would produce 0.0016 moles of H+. The amount of volcanic acid added (1.665m H2S04) in terms of the original concentrations (before the 1000-fold concentration) is equivalent to 0.00333 moles of H+. Together these two sources of acid add up to 0.00493 moles, which is more than enough to neutralize all the original alkalinity (0.00446 moles, Table 5.3). However, acids would also be neutralized by reaction with primary minerals (Eq. 5.4). Based on the prevalence of carbonates, especially siderite, in Martian meteorites... 

Becker L., Popp B., Rust T., and Bada J. L. (1999) The origin of organic matter in the martian meteorite ALH84001. Earth Planet. Sci. Lett. 167, 71-79. 

Mittlefehldt D. W., Lindstrom D. J., Lindstrom M. M., and Martinez R. R. (1999) An impact-melt origin for lithology A of martian meteorite Elephant Moraine A79001. Meteorit. Planet. Sci. 34, 357—368. 

Warren P. H. and Kallemeyn G. W. (1997) Yamato-793605, EET79001, and other presumed martian meteorites compositional clues to their origins. Proc. NIPR Symp. Antarctic Met. 10, 61-81. 

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