1. Younger Age for Oldest Martian Meteorite Ancient Martian Meteorite COSMOCHEMISTRY iLLUSTRATED Long Geologic History Formation by crystal accumulation in a magma chamber Shocked and crushed by impact Aqueous alteration and deposition of carbonate globules Isotopic systems, hence ages, affected by shock and alteration

2. Younger Age for Oldest Martian Meteorite Ancient Martian Meteorite COSMOCHEMISTRY iLLUSTRATED Igneous formation age of ALH84001 is 4.09 Ga, much younger than the previously-reported Sm-Nd age of 4.50 Ga.

3. Younger Age for Oldest Martian Meteorite Ancient Martian Meteorite COSMOCHEMISTRY iLLUSTRATED Next step: Reconcile igneous, impact, and alteration events recorded in ALH84001 with ages of impact basins on Mars.