A new 1.3 aeon-young achondrite

The ⁴⁰Ar/³⁹Ar age of Governador Valadares, a newly identified Nakhlite-achondrite, has been determined to be 1.32 ±.04 × 10⁹ yrs. The K-Ar age and cosmic ray exposure age of Governador Valadares is essentially identical to analogous ages for the two other known Nakhlite-achondrites and to Rb-Sr ages determined for Nakhla. These data suggest that all three known meteorites of this class were derived from the same parent body by a common event, and confirm that Governador Valadares is a member of this class. The most probable heat source for producing such meteorites may be collisional melting of a portion of the parent body. Nakhlites may represent a rare phenomenon and may not be at all representative of the surface of their parent body.