Reflectance spectra of hydrated Titan tholins at cryogenic temperatures and implications for compositional interpretation of red objects in the outer Solar System

We report the visible and near-infrared (0.4–2.5 μm) laboratory bidirectional reflectance of hydrated Titan tholin at cryogenic temperatures (∼100–300 K). When compared with room temperature measurements, the visible and near-infrared color of hydrated Titan tholin becomes bluer by ∼14% at low temperatures in the 0.7–1.0 μm region. Assuming the observed color changes are representative of tholin-like materials we estimate the influence of such color changes on the interpretation of the Centaur Pholus and find that the modest color changes will not significantly alter existing interpretations.