Spectral reflectance variations of aubrites, metal-rich meteorites, and sulfides: Implications for exploration of (16) Psyche and other “spectrally featureless” asteroids

The 350–2500 nm reflectance spectra of five enstatite achondrites (aubrites), five metal-rich chondrites (CBa, CBb, CH/CBb, and ungrouped), and seven sulfide mineral samples (three troilites, pyrrhotite, pentlandite, a mixture of pentlandite and chalcopyrite, and oldhamite) have been measured to search for spectral parameters that may offer insight into the surface composition of so-called “spectrally featureless” asteroids. Spectral data were acquired from powders, slabs, and hand samples. Aubrites exhibit high reflectance, generally positive slopes at visible wavelengths, and low-to-negative infrared slopes, consistent with E-/Xe-type asteroids. The metal-rich chondrites exhibit low reflectance, moderate visible slopes, and low near-infrared slopes, somewhat consistent with M−/X-complex asteroids. The metal-rich chondrites exhibit absorption features at ~900 nm arising from Fe²⁺-bearing silicates. Sulfides exhibit low to moderate reflectance and high visible and near-infrared slope, intermediate to the T- and L-type asteroids. The D-type asteroids, which have high visible and near-infrared slopes, are not well-matched by sulfides. Spectral data of the largest M−/X-type asteroid, (16) Psyche, are consistent with both powder from the Isheyevo CH/CBb chondrite and powder of meteoritic troilite. The data presented here will support interpretation of data returned from future spacecraft missions to “spectrally featureless” asteroids, like the Psyche, Lucy, and DART/Hera missions.