Color Variations on Asteroid (101955) Bennu

ct- NASA's OSIRIS-REx is a sample return mission to near-Earth B-type [1] asteroid (101955) Bennu [2]. Spectral variations on Bennu are subtle and associated with albedo [3]. We seek to classify the causes behind these spectral variations. By comparing the VIS-NIR spectral parameters of lab analogs [4] to those of Bennu, we find that decreasing grain size leads to spectral reddening and brightening [5]. However, studies predict that solar wind bombardment of organics (confirmed to be found on Bennu [6]) leads to spectral reddening, darkening and flattening [7] along with an upturn in UV albedo [8] -- all of which are detected on Bennu [9--11]. We thus infer that solar wind is a likely surface maturation process on Bennu, working against grain size effects. References [1] Clark, B.E. et al. (2011), \textit{Icarus }\textbf{216}(2), 462--475. [2] Lauretta, D.S. et al. (2017), \textit{Space Science Reviews }\textbf{212}(1-2), 925--984. [3] Clark, B.E. et al. (2019), \textit{EPSC }\textbf{2019}, EPSC--DPS2019. [4] Cloutis, E.A. et al. (2020), \textit{EPSC }\textbf{2020}, p. 975. [5] Sen, A. et al. (in review), \textit{Meteoritics {\&} Planetary Science}. [6] Simon, A.A. et al. (2020), \textit{Science}, \textbf{370}, eabc3522. [7] Moroz, L. et al. (1998), \textit{Icarus }\textbf{134}(2), 253--268. [8] Brunetto, R. et al. (2015), \textit{Asteroids IV, }597--616. [9] Fornasier, S. (2020), Astronomy {\&} Astrophysics, 644, A142. [10] Neumann, G. et al. (2020), LPS LI, (2326), 2032. [11] Hendrix, A.R. {\&} Vilas, F. (2019), \textit{Geophysical Research Letters }\textbf{46}(24), 14307--14317.