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

Grundy, W. M. and Keane, J. T. (2020) Color, composition, and thermal environment of Kuiper Belt object (486958) Arrokoth. Science, 367 (6481). Art. No. eaay3705. ISSN 0036-8075. doi:10.1126/science.aay3705.

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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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Keane, J. T.0000-0002-4803-5793
Additional Information:© 2020 American Association for the Advancement of Science. Received 12 June 2019; accepted 22 January 2020. Published online 13 February 2020. We gratefully thank the many hundreds of people who worked together on the New Horizons team. Their hard work enabled the encounter. Funding: Supported by NASA’s New Horizons project via contracts NASW-02008 and NAS5-97271/TaskOrder30. JJK was supported by the National Research Council of Canada. SK acknowledges the support of a Hubble Fellowship, program number HST-HF2-51394.002 provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. MR acknowledges support by the NASA Astrobiology Institute under Cooperative Agreement Notice NNH13ZDA017C issued through the Science Mission Directorate. BS, LG, and EQ acknowledge support by the French Centre National d’Etudes Spatiales (CNES). OMU acknowledges NASA Astrophysics Theory Program Grant Number NNX17AK59G for partial support of this work. Author contributions: WMG led authorship of the manuscript. WMG, CJAH, CBO, AHP, and SP analyzed the MVIC color data and wrote that section. WMG, AHP, SP, JCC, and DPC analyzed the LEISA spectral data and wrote that section. MKB and IRL analyzed the REX data and wrote that section. OMU did the thermal modeling and wrote that section, with input from WMG, CJAH, and LAY. WMG, DPC, DTB, SK, and MR wrote the implications section. CMDO, JJK, JTK, YJP, SBP, FS, JRS, SAS, AJV, and HAW contributed to data analysis and development of scientific ideas. All authors played roles in experimental design and/or provided feedback and insights on drafts of the manuscript. We declare no competing interests. Data and materials availability: All images, spacecraft data, and the shape model used in this paper are available at and at The three Charon observations used in flat-fielding the LEISA data are available at,, and Additional fully calibrated New Horizons data and higher-order data products will be released by the NASA Planetary Data System at in a series of stages in 2020 and 2021, due to the time required to fully downlink and calibrate the data.
Funding AgencyGrant Number
National Research Council of CanadaUNSPECIFIED
NASA Hubble FellowshipHST-HF2-51394.002
Centre National d’Études Spatiales (CNES)UNSPECIFIED
Issue or Number:6481
Record Number:CaltechAUTHORS:20200218-133326572.741
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Official Citation:Color, composition, and thermal environment of Kuiper Belt object (486958) Arrokoth. BY W. M. GRUNDY, M. K. BIRD, D. T. BRITT, J. C. COOK, D. P. CRUIKSHANK, C. J. A. HOWETT, S. KRIJT, I. R. LINSCOTT, C. B. OLKIN, A. H. PARKER, S. PROTOPAPA, M. RUAUD, O. M. UMURHAN, L. A. YOUNG, C. M. DALLE ORE, J. J. KAVELAARS, J. T. KEANE, Y. J. PENDLETON, S. B. PORTER, F. SCIPIONI, J. R. SPENCER, S. A. STERN, A. J. VERBISCER, H. A. WEAVER, R. P. BINZEL, M. W. BUIE, B. J. BURATTI, A. CHENG, A. M. EARLE, H. A. ELLIOTT, L. GABASOVA, G. R. GLADSTONE, M. E. HILL, M. HORANYI, D. E. JENNINGS, A. W. LUNSFORD, D. J. MCCOMAS, W. B. MCKINNON, R. L. MCNUTT JR., J. M. MOORE, J. W. PARKER, E. QUIRICO, D. C. REUTER, P. M. SCHENK, B. SCHMITT, M. R. SHOWALTER, K. N. SINGER, G. E. WEIGLE II, A. M. ZANGARI. Science 28 Feb 2020: Vol. 367, Issue 6481, eaay3705 DOI: 10.1126/science.aay3705
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:101330
Deposited By: Tony Diaz
Deposited On:18 Feb 2020 21:48
Last Modified:01 Jun 2023 23:31

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