Stephanie C. Werner¹, Anouck Ody², François Poulet³

¹The Centre for Earth Evolution and Dynamics, University of Oslo, Sem Sælandsvei 24, 0371 Oslo, Norway.
²Laboratoire de Géologie de Lyon: Terre, Planètes, Environnement, Université de Lyon 1 (CNRS, ENS-Lyon, Université de Lyon), rue Raphaël Dubois 2, 69622 Villeurbanne, France.
³Institut d’Astrophysique Spatiale, Université Paris Sud 11, Bâtiment 121, 91405 Orsay, France.

Absolute ages for planetary surfaces are often inferred by crater densities and only indirectly constrained by the ages of meteorites. We show that the <5 million-year-old and 55-km-wide Mojave Crater on Mars is the ejection source for the meteorites classified as shergottites. Shergottites and this crater are linked by their coinciding meteorite ejection ages and the crater formation age and by mineralogical constraints. Because Mojave formed on 4.3 billion–year-old terrain, the original crystallization ages of shergottites are old, as inferred by Pb-Pb isotope ratios, and the much-quoted shergottite ages of <600 million years are due to resetting. Thus, the cratering-based age determination method for Mars is now calibrated in situ, and it shifts the absolute age of the oldest terrains on Mars backward by 200 million years.

Reference
Werner SC, Ody A and Poulet F (2014) The Source Crater of Martian Shergottite Meteorites. Science 343:1343-1346.
[doi:10.1126/science.1247282]
Reprinted with permission from AAAS

Link to Article