An unusual lunar origin and chondritic refractory Antarctic micrometeorites

• Micrometeorites are capable of sampling a wide range of Solar System objects. • A small proportion of micrometeorites (∼1%) is also dust originating from achondrites. • Identifying achondritic particles is problematic due to changes from heating and ablation during atmospheric entry. • This study reports the first evidence of a lunar component in Antarctic micrometeorites. We report unearthing the first silicate-type (S-type) lunar Antarctic micrometeorites (AMM) spherule and another spherule with a refractory chondritic phase. The lunar spherule is made of Augite with minor Ni magnetite (<1 wt.%), in contrast to other known cosmic spherules. The Augite’s minor oxide range in the spherule are as follows: Wo 37-41 En 25-27 Fs 34-36 , Al 2 O 3 : 0.7–1 wt.%, Cr 2 O 3 : 0.01–0.06 wt.%, MnO: 0.32–0.39 wt.% and TiO 2 : 0.03–0.09 wt.%. The lunar spherule’s chemical characteristics indicate that it originated from very low Ti lunar basalt (VLT) mare basalts. Chondritic diopside (Wo 46-47 En 50-47 Fs 5-6 , Al 2 O 3 : 1.7–1.6 wt.%, Cr 2 O 3 : 0.6–0.63 wt.%, MnO: 0.2–0.4 wt.%, and TiO 2 : 0.0–0.02 wt.%) makes up the refractory phase in the second spherule. The chemical composition of diopside is indistinct from those of calcium aluminium inclusion (CAIs) found in both ordinary and carbonaceous chondrites. Our finding reveals that micron-sized lunar impact debris can potentially reach the Earth’s surface, similar to the earliest formed nebulae solid component.