The Thickness and Scale of Late-stage Basalts in Oceanus Procellarumtwo

Oceanus Procellarum, the largest lunar mare, is distributed with a large area of the late-stage (Eratosthenian) basalts. Research on the thickness, volume, and eruption flux of the late-stage basalts is essential for understanding the late thermal evolution of Oceanus Procellarum, even the Moon. The Eratosthenian basalts are rich in olivine and ilmenite, while the underlying Imbrian basalts are rich in pyroxene. Their significant spectral differences are easy to be distinguished using the hyperspectral data. We determine whether a crater has penetrated the overlying basalt layer by the data of Moon Mineralogy Mapper (M3), and estimate the thickness of Eratosthenian basalts in the Oceanus Procellarum region by using a crater excavation technique. A high-resolution thickness distribution map of the last-stage basalts within the Oceanus Procellarum has been acquired. The results show that the averaged thickness of Eratosthenian basalts in the Oceanus Procellarum region varies from (24±2) m to (88±2) m. Among them, the thickness of Eratosthenian basalts in the western Aristarchus is the greatest (>60m), whereas the southernmost area of the study has a minimum thickness of about 28–31m. The basalt thickness at the Chang’e-5 potential landing site Mons Rümker is about 31–38m. The thickness of Eratosthenian basalts in the east of Marius is about 35–45m, which is much smaller than the value of 100∼300m estimated by Weider et al. The total volume of Eratosthenian basalts is estimated to be ∼1.39×104km3, which is only about 1.6% of total basalts in Oceanus Procellarum. This indicates that the magmatism in the Eratosthenian period has been greatly weakened compared to the Imbrian period.