Nakhlites are unbrecciated , olivine - bearing clinopyroxenites that probably came from Mars . A total of eight nakhlites have been identified , including five recent finds : two samples ( 104 g and 456 g ) from the hot desert of Morocco ( NWA 817 and NWA 998 ) , and three samples , a total weight of approx.15 kg , from the Yamato Mountains of Antarctica ( Y000593 , Y000749 and Y000802 ) . Preliminary isotopic results for Y000593 have been given by Shih et al .. In this report , we present Rb - Sr and Sm - Nd isochron data for Y000593 and discuss the age correlation with other nakhlites and the timing of aqueous alteration on Mars .