Near-infrared spectroscopy of (93) Minerva with the Lowell discovery telescope + near-infrared high throughput spectrograph: More evidence for widespread primitive materials

Abstract We present rotationally resolved spectroscopy of asteroid (93) Minerva using the Lowell Discovery Telescope with the Near-Infrared High Throughput Spectrograph (NIHTS). We obtained spectroscopy over ~34% of the asteroid's rotation period. Minerva has been shown to be spectrally similar to primitive carbonaceous chondrites (e.g., McAdam et al., 2018, Icarus 306, 32–49) indicating it has amorphous materials on its surface. The extent to which these materials appear over Minerva's surface could provide constraints on the asteroid's formation time and/or directly relate the asteroid to a chemical group of carbonaceous chondrite meteorites. Parent asteroids are thought to preserve primitive meteorites in either an outer shell of material or by avoiding parent body processing (e.g., accreting after the peak heat flux of 26Al or before the introduction of exogenous 26Al to the Solar System). These two scenarios are expected to have different properties: the no processing scenario produces an asteroid with a compositionally homogenous surface and interior while the outer shell scenario would have compositionally distinct surface and interior. Over the observed region, we report that Minerva's surface appears to have amorphous materials, potentially indicating a homogeneous surface. However, more data are needed to determine Minerva's compositional uniformity and which formation scenario is most appropriate.