Ionizing Radiation Exposure On Arrokoth Shapes A Sugar World

The flyby of the New Horizons spacecraft of the Kuiper Belt Object Arrokoth revealed its reddish appearance and unraveled the unexpected presence of a methanol-rich surface.

However, the chemical compositions and fundamental processes responsible for the surface coloring have remained ambiguous.

Here, we have evidence that methanol ices exposed to galactic cosmic rays can replicate the colors of Arrokoth. Organics formed indicate that Arrokoth is rich in sugars including biologically significant ribose and glucose, while aromatic hydrocarbons are essential in producing the ultrared color slopes.

Our findings provide insights into the surface evolution of planetesimals in the early Solar System ranging from the Kuiper Belt to Oort’s clouds as repositories of short and long-periodic comets.

Sugars and related compounds detected in the residue of methanol ices irradiated at 40 K by two-dimensional gas chromatography along with their detailed structure. (A) Sugar and related compounds detected as BSTFA derivatives in the irradiated methanol residue resolved on a Chirasil-Dex column in the first dimension coupled to a DB Wax in the second dimension. Mass-to-charge ratios (m/z) 104, 193, 206, 215, 220, 294, and 323 are displayed. 1D and 2D represent the first-dimension and second-dimension times of the columns, respectively. (B) Detailed structures are identified in the residues by means of two-dimensional gas chromatography. Structures of the chiral molecules represent the d-enantiomer. Names of molecules are color-coded according to the number of carbon atoms: two carbon atoms (C2) orange, C3 blue, C4 black, C5 green, and C6 red. The quantities of 23 molecules are given in SI Appendix, Table S10. — PNAS via PubMed

Ionizing radiation exposure on Arrokoth shapes a sugar world, PNAS via PubMed (open access)

Astrobiology, Astrochemistry,