Origin of Alkylphosphonic Acids in the Interstellar Medium

Origin of alkylphosphonic acids in the interstellar medium Andrew Turner, Matthew Abplanalp, Alexandre Bergantini, Robert Frigge, Cheng Zhu, Bing-Jian Sun, Chun-Ta Hsiao, Agnes Chang, Cornelia Meinert, Ralf Kaiser To cite this version: Andrew Turner, Matthew Abplanalp, Alexandre Bergantini, Robert Frigge, Cheng Zhu, et al.. Origin of alkylphosphonic acids in the interstellar medium. Science Advances , American Association for the Advancement of Science (AAAS), 2019, 5 (8), pp.eaaw4307. 10.1126/sciadv.aaw4307. hal-02322418 HAL Id: hal-02322418 https://hal.archives-ouvertes.fr/hal-02322418 Submitted on 17 Aug 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. SCIENCE ADVANCES | RESEARCH ARTICLE GEOCHEMISTRY Copyright © 2019 The Authors, some rights reserved; Origin of alkylphosphonic acids in the exclusive licensee American Association interstellar medium for the Advancement Andrew M. Turner1,2, Matthew J. Abplanalp1,2, Alexandre Bergantini1,2, Robert Frigge1,2, of Science. No claim to 1,2 3 3 3 4 original U.S. Government Cheng Zhu , Bing-Jian Sun , Chun-Ta Hsiao , Agnes H. H. Chang *, Cornelia Meinert *, Works. Distributed 1,2 Ralf I. Kaiser * under a Creative Commons Attribution For decades, the source of phosphorus incorporated into Earth’s first organisms has remained a fundamental, NonCommercial unsolved puzzle. Although contemporary biomolecules incorporate P(+V) in their phosphate moieties, the limited License 4.0 (CC BY-NC). bioavailability of phosphates led to the proposal that more soluble P(+III) compounds served as the initial source of phosphorus. Here, we report via laboratory simulation experiments that the three simplest alkylphosphonic acids, soluble organic phosphorus P(+III) compounds, can be efficiently generated in interstellar, phosphine-doped ices through interaction with galactic cosmic rays. This discovery opens a previously overlooked avenue into the formation of key molecules of astrobiological significance and untangles basic mechanisms of a facile synthesis of phosphorus-containing organics in extraterrestrial ices, which can be incorporated into comets and asteroids before Downloaded from their delivery and detection on Earth such as in the Murchison meteorite. INTRODUCTION A notable class of molecules that has these characteristics of an 3− While phosphates (PO4 ) along with their P(+V) derivatives present impending abiotic synthesis in extraterrestrial ices are alkylphosphonic http://advances.sciencemag.org/ the ubiquitous form of phosphorus for contemporary biochemistry acids [R─P(O)(OH)2], with “R” signifying an alkyl group (CnH2n+1). due to their unique properties (1), the increased solubility of reduced These molecules represent the only phosphorus-containing organic oxidation states such as P(+III) under Earth’s early, oxygen-poor compounds of extraterrestrial origin identified thus far (8). Alkyl- atmospheric conditions has been proposed as the initial source of phosphonic acids—which carry methyl (CH3), ethyl (C2H5), isopropyl/ prebiotic phosphorus available for the first terrestrial microorganisms n-propyl (C3H7), and n-butyl (C4H9) chains—were identified in the (2). Phosphorus-bearing biomolecules include RNA/DNA, adenosine Murchison meteorite and exhibit the carbon-phosphorus bond that diphosphate/adenosine triphosphate (ADP/ATP), and phospholipids; Cooper et al. (8) noted would be critical to survive aqueous alteration in each case, a phosphate group is chemically bonded to a carbon on the parent body. Thus, alkylphosphonic acids represent both a atom of a sugar, ribose (RNA and ADP/ATP) and deoxyribose (DNA), soluble and bioavailable source of phosphorus that could persist on or of glycerol (phospholipids). The Murchison meteorite, a carbon- an aqueously altered body before their delivery to Earth as well as aceous chondrite carrying key classes of exogenously synthesized the potential for the formation of phosphate esters in extraterrestrial on October 21, 2019 organic molecules such as amino acids and sugars (3), contains bodies without aqueous alteration. While phosphorus-bearing minerals phosphorus as phosphide (−III) and phosphate (+V) minerals (4). such as schreibersite have been investigated as a source of alkyl- Schreibersite, an iron-nickel phosphide [(Fe,Ni)3P] mineral found phosphonic acids (5, 9–11), the unique potential of an alternative in meteorites, has been studied as a possible source of phosphite formation scenario, the synthesis of alkylphosphonic acids in phosphorus- − [H2PO3 , P(+III)] minerals contained in ancient Archean carbonaceous doped ices condensed on interstellar grains in cold molecular clouds deposits and, given the 103-fold greater solubility of phosphite over through interaction with ionizing radiation, has not been fully explored phosphate minerals, as the ultimate origin of soluble prebiotic phos- yet. Functional groups, which might be linked to alkylphosphonic phorus (5). While a purely terrestrial hypothesis might state that no acids, have been proposed in processed phosphine (PH3)–rich ices “phosphorus problem” exists and that organisms could have scavenged by infrared spectroscopy (7). However, any discrete alkylphosphonic the limited phosphorus from geologic phosphates (2), an extra- acids were not identified in this study (7) because the overlapping terrestrial view advocates that meteoric minerals were delivered to absorption bands of these complex organic molecules prevent their Earth during the heavy bombardment period and, after aqueous unambiguous detection (12). The organic chemistry of carbonaceous processing, formed soluble phosphites that were available to the chondrites such as Murchison is consistent with icy bodies having first organisms (5). An alternative to these hypotheses considers key at least partially interstellar organic matter (3). In addition, interstellar chemical reactions essential to produce complex, biologically relevant analog ices have shown the potential to yield complex organic molecules organic molecules in astrophysical environments such as in inter- of biochemical relevance from fundamental biomolecules such as stellar ices in deep space before their delivery to Earth (6, 7). amino acids (13) to simple sugars (14). These interstellar compounds can be incorporated eventually into planetesimals, comets, and asteroids (8). Phosphine (PH3) presents a promising phosphorus source 1Department of Chemistry, University of Hawaii at Manoa, Honolulu, HI 96822, USA. for these interstellar ices, as phosphine has been observed in the 2W.M. Keck Laboratory in Astrochemistry, University of Hawaii at Manoa, Honolulu, circumstellar envelope of the carbon star IRC+10216 (15), from which HI 96822, USA. 3Department of Chemistry, National Dong Hwa University, Shoufeng, it can be ejected to the interstellar medium and may eventually 4 Hualien, Taiwan. Université Côte d’Azur, Institut de Chimie de Nice, UMR 7272 become incorporated into cold molecular clouds and, hence, icy CNRS, 06108 Nice, France. *Corresponding author. Email: [email protected] (R.I.K.); [email protected]. grains. In addition, phosphine might be formed on interstellar grain tw (A.H.H.C.); [email protected] (C.M.) surfaces from atomic phosphorus and atomic hydrogen in a manner Turner et al., Sci. Adv. 2019; 5 : eaaw4307 7 August 2019 1 of 7 SCIENCE ADVANCES | RESEARCH ARTICLE analogous to the formation of water from atomic oxygen and atomic vacuum ultraviolet photoionization and mass resolved by PI-ReTOF-MS hydrogen (16). These phosphine molecules would immediately be- to identify the synthesized alkyl phosphorus oxoacids and their come a component of icy grain mantles. Note that in molecular clouds, structural isomers selectively. The solid residues that remained at gas phase routes to phosphine are closed. Furthermore, phosphine room temperature were analyzed after derivatization exploiting has been assigned as the carrier of the phosphorus signal detected in two-dimensional gas chromatography coupled with ReTOF-MS comet 67P/Churyumov-Gerasimenko in the framework of the Rosetta (GC×GC-TOF-MS). mission (17). Likewise, interstellar analog ices of phosphine-water exposed to ionizing radiation generate a homolog series of phosphorus oxoacids including phosphonic acid (H3PO3), phosphoric RESULTS acid (H3PO4), and pyrophosphoric acid (H4P2O7) (18). Therefore, Infrared spectroscopy of irradiated ices represents a valuable tool the addition of organic carbon to these interstellar ice analogs could for identifying small, individual molecules and functional groups of provide the critical reactant necessary to establish the plausible for- phosphorus-bearing molecules (23). The exploitation of water-rich mation of alkylphosphonic acids in extraterrestrial ices. ices (PH3:H2O:CH4, 1:10:2) in our experiments is appropriate for Here, we present compelling evidence on the synthesis of the three analog ices, since water serves as a major constituent of interstellar simplest alkyl phosphorus oxoacids—methyl (CH3), ethyl (C2H5), ices (24). However, as a strong infrared

Load more