The SNCs are a class of  about ~30 meteorites thought to be derived from Mars.  They were initially recognized to be unusual meteorites by their young formation ages (~4 billion to ~200 million years ago), and then unambiguously association with Mars by remarkable agreement between relative abundances of trapped gases  in the rocks (particularly the noble gases) and the Martian atmosphere as observed by Viking in 1976 (see Pepin, 1985).

As a follow up to our 2002 study of ALH84001, Ben P. Weiss (MIT) and I are using ⁴⁰Ar/³⁹Ar thermochronology and (U-Th)/He and ⁴He/³He thermochronometry on a suite of SNC meteorites to constrain possible thermal scenarios for the Martian samples.  We have heavily relied upon decades worth of published work and the Ar data generously provided by both Tim Swindle (UA) and Don Bogard (NASA) and their colloeagues.

The objective of this study is two-fold: (i) to constrain the peak thermal perturbations associated with ejection from the Martian surface and entry into Earth’s atmosphere, and (ii) to place constraints on the thermal conditions of the rocks while near the Martian surface.  In many ways, the latter approach is similar to work done on terrestrial samples.  However in the case of Mars, a constraint to even an order of magnitude can be useful!