Meteorite ALH

Could it be the case that microorganisms, like the suspected fossils in the Mars meteorite ALH 84001, exist in the Martian soil This question leads to the counterquestion as to whether it has previously been possible to detect and study life (primitive life forms) under highly extreme conditions. Are there such conditions on Earth We now know quite a lot about extremophiles such as the thermophilic, halophilic and hyperthermophilic microorganisms. 

McKay DS, et al. (1996) Search for past life on Mars possible relic biogenic activity in martian meteorite ALH 84001. Science 273 924-930... 

Romanek CS, et al. (1994) Record of fluid-rock interaction on Mars from the meteorite ALH 84001. Nature 372 655-657... 

Valley JW, EUer JM, Graham CM, Gibson EK, Romanek CS, Stolper EM (1997) Low temperature carbonate concretions in the martian meteorite ALH 84001 evidence from stable isotopes and mineralogy. Science 275 1633-1637... 

The C03 meteorites have been subdivided into metamorphic grades from 3.0 to 3.7, with peak temperatures in the range 450-600 °C (Rubin, 1998). In contrast to the metamorphism of the ordinary chondrites, the CO metamorphism probably occurred in the presence of water, and the system was not closed with respect to oxygen. The least metamorphosed CO meteorites, ALH 77307 and Y 81020, are the most 0-rich Loongana 001 and HH 073, classified as 3.8 or 4, are the most 0-poor. There is not, however, a simple one-to-one correspondence between metamorphic grade and isotopic composition. Since most of the CO chondrites are finds, some may have been altered by terrestrial weathering. 

The surface of Mars is covered by meteorite craters, some up to 200 km in diameter. The question as to whether water exists on Mars has been the subject of scientific controversy for many years (see Chap. 11). Costly Mars missions with the goal of mapping the surface have afforded important results on now dry river valleys. The weather on Mars is characterized by ground-level fog, thin ice clouds and (often very violent) dust storms, which vary not only seasonally but also daily. The question as to whether our neighbour planet harbours life (of any kind), or if it ever did so, gave rise to a media sensation at a NASA press conference on August 7, 1996. The researchers, who had been studying the 1.9 kg Mars meteorite ALH 84001, came to the conclusion that it bore clear evidence of previous life forms ... 

Fig. 18.29 Fracture surfaces in the martian meteorite ALH 84001 are lined with carbonate globules and tube-like structures which were tentatively identified by McKay et al. (1996) as evidence for the existence of micro-organisms on Mars. However, the evidence is not conclusive because an abiogenic origin of these features cannot be excluded (Courtesy of NASA and of the Johnson Space Flight Center, Houston, Texas)...

Becker L, Bopp B, Rust T, Bada JL (1999) The origin of organic matter in martian meteorite ALH 84001. Earth Planet Sci Lett 167 71-79... 

Harvey RP (2003) The origin and significance of Antarctic meteorites. Chemie der Erde 63 93-147 Harvey RP, Maurette M (1990) The best cosmic dust source in the world The origin and significance of the Walcott Neve, Antarctica, micrometeorites. Lunar and Planetary Science Conference, vol. 21—. LPI, Houston, TX, pp 569-578 Harvey RP, McSween HY Jr (1996) A possible high-tempera-ture origin for the carbonates in the martian meteorite ALH 84001. Nature 382 49-51... 

Kent AJR, Hutcheon ID, Ryerson FJ, Phinney DL (2001) The temperature of formation of carbonate in martian meteorite ALH 84001. Geochim Cosmochim Acta 65(2) 311-321... 

Kirschvink JL, Maine AT, Vali H (1997) Paleomagnetio evidence of a low-temperature origin of carbonate in the martian meteorite ALH 84001. Science 275 1629-1633 Klein HP (1978) The Viking biological experiment on Mars. Icarus 34 666-674. 

Shearer CK, Lane GD, Papike JJ, Spilde MN (1996) Sulfur isotope systematics in alteration assemblages in martian meteorite ALH 84001. Geochim Cosmochim Acta 60 2921-2926... 

Terada K, Yada T, Kojima H, and 21 additional persons (2001) General characterization of Antarctic micrometeorites collected by the 39th Japanese Antarctic Research Expedition Consortium studies JARE AMMs (II). Antarctic Meteorite Res 14 89-107, Tokyo, Japan Terada K, Monde T, Sano Y (2003) Ion microprobe U-Th-Pb dating of phosphates in martian meteorite ALH 84001. Meteorit Planet Sd 28(11) 1697-1703 Thiel E, Schmidt RA (1961) Spherules from the Antarctic ice cap. J Geophys Res 66 307-310 Thomas-Keprta KL, McKay DS, Wentworth SJ, Stevens TO, Taunton AE, Allen CC, Coleman A, Gibson EK Jr, Romanek... 

Turner G, Knott FS, Ash RD, Gilmour JD (1997) Ar-Ar chronology of the martian meteorite ALH 84001 Evidence for the timing of the early bombardment of Mars. Geochim Cosmochim Acta 61 3835-3850 Ugolini FC, Jackson ML (1982) Weathering and mineral synthesis in Antarctic soils. In Craddock C (ed) Antarctic geoscience. University of Wisoconsin Press, Madison, WI, pp 1101-1109... 

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