October 14, 2014

The Source Crater of Martian Shergottite Meteorites

Stephanie C. Werner, Anouck Ody and François Poulet
Science Express on March 6th 2014 / Science on March 14th 2014 doi:10.1126/science.1247282

Summary: 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 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 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 < 600 million years shergottite ages are due to resetting. Thus, the cratering-based age determination method for Mars is now calibrated in situ, and shifts the absolute age of the oldest terrains of Mars backward by 200 million years.