Lava flow ages in northeastern Oceanus Procellarum: The need for calibrating crater counting procedures

The Northeastern Oceanus Procellarum (NE-OP) study area is a patchwork of lava flows that range in model age from 1.4–3.5 Ga (average age for all count areas is 2.3 Ga), but whose FeO and TiO2 contents deviate little. The intermediate TiO2 content values (4.0–6.8 wt%) exhibited by the mare in this region represent material that is underrepresented in the current lunar sample collection. The model ages in the study region are bimodal (~2.2 Ga and ~3.0+ Ga), with eruption of lava flows at the Chang‘E-5 landing site occurring at ~3.0 Ga. By comparison, other investigators estimate the model age of the Chang‘E-5 site to be ~1.2 to 1.6 Ga. We find preliminary evidence that differences in measurement methodology may lead to disparate model ages and explain the difference in predicted model age of the Chang‘E-5 site.