The solar nebula origin of (486958) Arrokoth, a primordial contact binary in the Kuiper Belt

W B McKinnon; D C Richardson; J C Marohnic; J T Keane; W M Grundy; D P Hamilton; D Nesvorný; O M Umurhan; T R Lauer; K N Singer; S A Stern; H A Weaver; J R Spencer; M W Buie; J M Moore; J J Kavelaars; C M Lisse; X Mao; A H Parker; S B Porter; M R Showalter; C B Olkin; D P Cruikshank; H A Elliott; G R Gladstone; J Wm Parker; A J Verbiscer; L A Young; New Horizons Science Team

doi:10.1126/science.aay6620

The solar nebula origin of (486958) Arrokoth, a primordial contact binary in the Kuiper Belt

Science. 2020 Feb 28;367(6481):eaay6620. doi: 10.1126/science.aay6620. Epub 2020 Feb 13.

Authors

W B McKinnon¹, D C Richardson², J C Marohnic², J T Keane³, W M Grundy^{4

5}, D P Hamilton², D Nesvorný⁶, O M Umurhan^{7

8}, T R Lauer⁹, K N Singer⁶, S A Stern⁶, H A Weaver¹⁰, J R Spencer¹¹, M W Buie⁶, J M Moore⁷, J J Kavelaars¹¹, C M Lisse¹⁰, X Mao¹², A H Parker⁶, S B Porter⁶, M R Showalter⁸, C B Olkin⁶, D P Cruikshank⁷, H A Elliott^{13

14}, G R Gladstone¹³, J Wm Parker⁶, A J Verbiscer¹⁵, L A Young⁶; New Horizons Science Team

Affiliations

¹ Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University in St. Louis, St. Louis, MO 63130, USA. mckinnon@wustl.edu.
² Department of Astronomy, University of Maryland, College Park, MD 20742, USA.
³ Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.
⁴ Lowell Observatory, Flagstaff, AZ 86001, USA.
⁵ Department of Astronomy and Planetary Science, Northern Arizona University, Flagstaff, AZ 86011, USA.
⁶ Division of Space Science and Engineering, Southwest Research Institute, Boulder, CO 80302, USA.
⁷ NASA Ames Research Center, Space Science Division, Moffett Field, CA 94035, USA.
⁸ SETI Institute, Mountain View, CA 94043, USA.
⁹ National Optical-Infrared Astronomy Research Laboratory, National Science Foundation, Tucson, AZ 85726, USA.
¹⁰ Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA.
¹¹ National Research Council of Canada, Victoria, BC V9E 2E7, Canada.
¹² Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University in St. Louis, St. Louis, MO 63130, USA.
¹³ Division of Space Science and Engineering, Southwest Research Institute, San Antonio, TX 78238, USA.
¹⁴ Department of Physics and Astronomy, University of Texas, San Antonio, TX 78249, USA.
¹⁵ Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA.

PMID: 32054695
DOI: 10.1126/science.aay6620

Abstract

The New Horizons spacecraft's encounter with the cold classical Kuiper Belt object (486958) Arrokoth (provisional designation 2014 MU₆₉) revealed a contact-binary planetesimal. We investigated how Arrokoth formed and found that it is the product of a gentle, low-speed merger in the early Solar System. Its two lenticular lobes suggest low-velocity accumulation of numerous smaller planetesimals within a gravitationally collapsing cloud of solid particles. The geometric alignment of the lobes indicates that they were a co-orbiting binary that experienced angular momentum loss and subsequent merger, possibly because of dynamical friction and collisions within the cloud or later gas drag. Arrokoth's contact-binary shape was preserved by the benign dynamical and collisional environment of the cold classical Kuiper Belt and therefore informs the accretion processes that operated in the early Solar System.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

Associated data

figshare/10.6084/m9.figshare.11653167