Research Article

Color, composition, and thermal environment of Kuiper Belt object (486958) Arrokoth

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Science  13 Feb 2020:
eaay3705
DOI: 10.1126/science.aay3705

Abstract

The outer Solar System object (486958) Arrokoth (provisional designation 2014 MU69) has been largely undisturbed since its formation. We study its surface composition using data collected by the New Horizons spacecraft. Methanol ice is present along with organic material, which may have formed through irradiation of simple molecules. H2O ice is not detected. This composition indicates hydrogenation of CO-rich ice and/or energetic processing of CH4+H2O ices in the cold, outer edge of the early Solar System. There are only small regional variations in color and spectra across the surface, suggesting Arrokoth formed from a homogeneous or well-mixed reservoir of solids. Microwave thermal emission from the winter night side is consistent with a mean brightness temperature of 29 ± 5 K.

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