On a radiolytic origin of red organics at the surface of the Arrokoth Trans-Neptunian Object

Eric Quirico (1) , Aurore Bacmann (1) , Cédric Wolters (1) , Basile Augé (1) , Laurène Flandinet (1) , Thibault Launois (1) , John Cooper (2) , Véronique Vuitton (1) , Thomas Gautier (3, 4) , Lora Jovanovic (3) , Philippe Boduch (5) , Hermann Rothard (5) , Léopold Desage (1) , Alexandre Faure (1) , Bernard Schmitt (1) , Olivier Poch (1) , William Grundy (6) , Silvia Protopapa (7) , Sonia Fornasier (4, 8) , Dale Cruikshank (9) , S. Alan Stern (7)

1 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble
2 GSFC - NASA Goddard Space Flight Center
3 PLANETO - LATMOS
4 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics
5 CIMAP - UMR 6252 - Centre de recherche sur les Ions, les MAtériaux et la Photonique
6 Lowell Observatory [Flagstaff]
7 SwRI - Southwest Research Institute [Boulder]
8 IUF - Institut universitaire de France
9 UCF - University of Central Florida [Orlando]

The classical Kuiper Belt Object (KBO) Arrokoth was surveyed by the New Horizons spacecraft on 1st January 2019, revealing a small bilobed object with a red surface, whose spectral slope lies in the average of the whole KBOs population. This red color has been assigned to reddish organic materials, either inherited from the protosolar disk during accretion, or formed through radiolytic processes in the surface due to exposure to solar or interstellar photons, Solar Wind, Solar Energetic Particles or Galactic Cosmic Rays. We report here a study investigating the radiolytic scenario, based on numerical calculations and experimental simulations run with swift heavy ions (74.8 MeV¹³⁶Xe¹⁹⁺ and 33.06 MeV⁵⁸Ni⁹⁺), and low-energy 105 keV¹⁸O⁶⁺ions on CH₃OH ice, the only molecule identified at Arrokoth’s surface.

Mots clés: Trans-neptunian objects; Cosmic rays; Ices; organic chemistry; Spectroscopy

Domaines: Planète et Univers [physics]

Eric Quirico, Aurore Bacmann, Cédric Wolters, Basile Augé, Laurène Flandinet, et al.. On a radiolytic origin of red organics at the surface of the Arrokoth Trans-Neptunian Object. Icarus, 2023, 394 (April), pp.115396. ⟨10.1016/j.icarus.2022.115396⟩. ⟨insu-03901032⟩