Ionizing radiation exposure on Arrokoth shapes a sugar world

• 成果类型: Article
• 署名作者: Zhang, Chaojiang; Leyva, Vanessa; Wang, Jia; Turner, Andrew M.; Mcanally, Mason; Herath, Ashanie; Meinert, Cornelia; Young, Leslie A.; Kaiser, Ralf I.
• 署名单位: University of Hawaii System; University of Hawaii Manoa; University of Hawaii System; University of Hawaii Manoa; Universite Cote d'Azur; Centre National de la Recherche Scientifique (CNRS); CNRS - Institute of Chemistry (INC); Southwest Research Institute
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-14914
• DOI: 10.1073/pnas.2320215121
• 发表日期: 2024-06-11
• 关键词: kuiper-belt object; complex organic-molecules; ion irradiation; color diversity; tof-sims; interstellar; ices; SYSTEM; methane; SPACE

摘要

The Kuiper Belt object (KBO) Arrokoth, the farthest object in the Solar System ever visited by a spacecraft, possesses a distinctive reddish surface and is characterized by pronounced spectroscopic features associated with methanol. However, the fundamental processes by which methanol ices are converted into reddish, complex organic molecules on Arrokoth's surface have remained elusive. Here, we combine laboratory simulation experiments with a spectroscopic characterization of methanol ices exposed to proxies of galactic cosmic rays (GCRs). Our findings reveal that the surface exposure of methanol ices at 40 K can replicate the color slopes of Arrokoth. Sugars and their derivatives (acids, alcohols) with up to six carbon atoms, including glucose and ribose-fundamental building block of RNA-were ubiquitously identified. In addition, polycyclic aromatic hydrocarbons (PAHs) with up to six ring units ( 13 C 22 H 12 ) were also observed. These sugars and their derivatives along with PAHs connected by unsaturated linkers represent key molecules rationalizing the reddish appearance of Arrokoth. The formation of abundant sugar - related molecules dubs Arrokoth as a sugar world and provides a plausible abiotic preparation route for a key class of biorelevant molecules on the surface of KBOs prior to their delivery to prebiotic Earth.