High resolution mapping of TiO₂ abundances on the Moon using the Hubble Space Telescope

Samples of the lunar regolith returned by Apollo astronauts show large variations (0 to >10 wt%) in TiO₂ abundance indicating complex compositional zonation within the lunar mantle. A long held goal of the lunar science community is the accurate determination of TiO₂ abundances on the lunar surface through remote sensing methods. To date only limited progress has been made in this area using spacecraft spectral measurements acquired in visible through near-infrared wavelengths. Here we show that variations in the ratios of ultraviolet (UV) to visible (VIS) reflectances in images taken by the Hubble Space Telescope indicate a strong correlation with TiO₂ abundances determined from returned samples at the Apollo 17 landing site, and little correlation with the "maturity" of lunar soils. These new findings imply that UV-VIS observations may lead to an alternate and improved method of remotely mapping TiO₂-bearing materials (probably as ilmenite) across the lunar surface and enable more refined studies of lunar crustal composition, surface volcanism, and subsurface magma evolution processes. Additionally, accurate identification and quantification of TiO₂ rich deposits serves to guide future human exploration of the Moon.