Younger Age for Oldest Martian MeteoriteYounger 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

Younger Age for Oldest Martian MeteoriteYounger 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.

Younger Age for Oldest Martian Younger Age for Oldest Martian MeteoriteMeteorite

Ancient Martian Meteorite COSMOCHEMISTRY iLLUSTRATED

Next step: Reconcile igneous, impact, and alteration events recorded in ALH84001 with ages of impact basins on Mars.