Emplacement conditions of lunar impact melt flows

Hypervelocity impacts on terrestrial bodies have the potential to rapidly heat and redistribute silicate target material form impact melt flows. On Moon, a subset of deposits exited craters as laterally moving flows that moved away from crater rim under influence gravity. These exhibit similarities lava flows, but be superheated by cratering process. To estimate initial temperature (T0) thickness (H0) these we combine new remote sensing analyses, experimentally-derived rheological relationships for three lunar analog materials, numerical forward models flow emplacement identify combinations parameters yield matching observed length Moon. We focus four craters, which span range materials diameters (D): Giordano Bruno (D = 22.1 km), Necho 36.9 Tycho 85.3 Copernicus 96.1 km). modeled compositions—anorthosite, norite, basalt—emplaced cold ambient temperatures (Tambient –180 °C) place minimum bound cooling-limited emplacement. Results show lengths can achieved subliquidus melts emplaced within laminar regime. For high-density (0% vesicularity) melts, best-fit inversions T0 H0 mean values 1253.3 ± 149.8 °C 21.6 8.7 m, respectively; low-density (64% are 1343.3 87.8 27.9 5.7 m—with uncertainties reported at 1 standard deviation. Model results also temperatures, with 0 64% vesicularity would expected durations 76, 78, 174, 186 h Bruno, Necho, Tycho, Copernicus, respectively. Therefore, do not in super-liquidus gravity-driven lengths, times long enough majority self-secondary fragments land before fully emplaced. This suggests some may lava-like their dynamics differences populations adjacent ejecta differ significantly, providing more robust age young due presence fewer secondaries. Impact could still time formation, turbulence facilitate rapid entrainment external clasts, quickly lowering generate similar products effusive volcanic eruptions.