Martian Rocks in Antarctica

The original Nakhla stone attracted attention when Papanastassiou and Wasserburg (1974) reported that its Rb-Sr crystallization age is only 1.37 0.02 billion years, which was later confirmed by Gale et al. (1975) and by Nakamura et al. (1982). The anomalously low crystallization age distinguished Nakhla from most other meteorites and raised questions about its origin. 

Cassidy 2003, p. 109). This conclusion was strengthened in 1983 when ALHA 81005 was identified as a lunar meteorite that was blasted off the surface of the Moon by the impact of a meteorite from the asteroid belt (Melosh 1989 Section 18.9.1). If it happened on the Moon, it could also happen on Mars. 

The search for martian meteorites in Antarctica and in the hot deserts of the world continues because these meteorites are the only rocks from Mars that are presently available. The most recent information on the martian meteorites is contained in the books edited by Davis (2005) and by McFadden et al. (2006) and in the papers presented at a woikshop on the topic of unmixing of SNCs (Treiman 2003). 

The most important meteorite discovered in Antarctica in more than 25 years of searching was picked up by Roberta Score of t NSMET during the 1984/85 field-season on the Far Western ice field near the Allan Hills (Cassidy 2003). This specimen in Fig. 18.28 was named ALH 84001 and was identified as a diogenite achondrite (Table 18.1) weighing in at 1,930.9 g (Score and Lindstrom 1990). Nearly 10 years passed before 

David W. Mittlefehldt discovered that ALHA 84001 is actually a coarse grained cataclastic orthopyroxen-ite related to the martian SNC meteorites (Mittlefehldt 1994). In addition, Mittlefehldt reported the presence of two generations of carbonate minerals which could have formed at a moderately high temperature of about 700°C. 

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