SNC meteorites: Igneous rocks from Mars?

Abstract

All dated meteorites have formation ages of 4.4 to 4.6 b.y. (Sears, 1978), except for nine achondrites which crystallized 1.3 b.y. ago (Table 1). These meteorites-shergottites, nakhlites, and chassignites (SNC)-also differ chemically, petrologically, physically, and magnetically from other meteorite types, suggesting a unique origin. We propose, extending previous tentative suggestions (Wasson and Wetherill, 1979; Nyquist et al., 1979a; Walker et al., 1979; McSween and Stolper, 1980), that SNC meteorites are igneous rocks from Mars, and additionally, using the characteristics of SNC meteorites, we speculate on specific events in the history of Mars.