Schematic illustration with a gravity gradient map of the lunar nearside and a cross-section showing two ilmenite-bearing cumulate downwellings from lunar mantle overturn. Credit: Adrien Broquet/University of Arizona & Audrey Lasbordes
“Because these heavy minerals are denser than the mantle underneath, it creates a gravitational instability, and you would expect this layer to sink deeper into the moon’s interior,” said Weigang Liang, who led the research as part of his doctoral work at LPL. Did this material sink as it formed a little at a time, or all at once after the moon had fully solidified? Did it sink into the interior globally and then rise up on the near side, or did it migrate to the near side and then sink? Did it sink in one big blob, or several smaller blobs?
“Our analyses show that the models and data are telling one remarkably consistent story,” Liang said. “Ilmenite materials migrated to the near side and sunk into the interior in sheetlike cascades, leaving behind a vestige that causes anomalies in the moon’s gravity field, as seen by GRAIL.”