Complex Water-ice Mixtures on NII Nereid: Constraints from NIR Reflectance

Abstract Nereid, Neptune’s third-largest satellite, lies in an irregular orbit and is the only outer satellite system (apart from Triton) that can be spectroscopically characterized with current generation of Earth-based telescopes. We report our results on spectral characterization Nereid using its reflectance spectrum 0.8 to 2.4 μ m, providing first measurements over range 0.8–1.4 m. detect absorption features crystalline water ice close agreement previous measurements. show model fits simple intimate mixtures including do not provide simultaneous matches band depths at 1.5 2.0 m when accounting for continuum. Possible solutions include invoking a more complex continuum, both amorphous ice, allowing submicron-sized grains. magnetite CM2 chondrite Murchison flexible framework interpreting variation bodies neutral-sloped spectra like Nereid. Magnetite particular provides good match continuum without requiring presence tholin-like organics. note carbonaceous chondrites their components may useful analogs non-ice solar bodies, consistent recent findings by Fraser et al. Comparison large trans-Neptunian objects satellites Uranus Nereid’s low albedo, deep bands, neutral color distinct many other icy objects, but such comparisons are limited incomplete understanding variability among ∼100 km-sized bodies.