Unusual Ti minerals on the Moon produced by space weathering

Micrometeorite impacts are one of the main drivers of lunar space weathering and can alter the properties of lunar regolith. However, the details of such processes are not well understood yet. We used transmission electron microscopy to study a micrometeorite impact crater on a glass bead returned by Chang’e-5. We detected Ti-oxide deposits on the crater rim and identified their detailed structure as rutile (TiO 2 ), trigonal Ti 2 O and triclinic Ti 2 O. The trigonal Ti 2 O and triclinic Ti 2 O are newly discovered mineral phases in lunar samples. We show that these Ti-oxide deposits could have formed by vaporization or deposition processes following a high-velocity microimpact on the lunar regolith. We suggest that such Ti minerals are previously overlooked space-weathering products on the Moon. Similar alterations to photocatalytic properties and reflectance spectra of regolith may also happen on other airless planetary bodies in the Solar System.