Processing of 72-K water-rich ices by keV and MeV oxygen ions: implications for the Saturnian moon Enceladus

Autor(es)

Rachid, M. G. ^{[1, 2]} ; Pilling, S. ^[2] ; Rocha, W. R. M. ^{[2, 3, 4]} ; Agnihotri, A. ^[5] ; Rothard, H. ^[5] ; Boduch, P. ^[5]

Afiliação do(s) autor(es)

^[1] Leiden Univ, Leiden Observ, POB 9513, NL-2300 RA Leiden - Netherlands

^[2] Univ Vale Paraiba UNIVAP, Lab Astroquim & Astrobiol LASA, At Shishima Hifumi 2911, BR-12244000 Sao Jose Dos Campos, SP - Brazil

^[3] Univ Copenhagen, Niels Bohr Inst, Oster Voldgade 5-7, DK-1350 Copenhagen - Denmark

^[4] Univ Copenhagen, Ctr Star & Planet Format, Oster Voldgade 5-7, DK-1350 Copenhagen - Denmark

^[5] Normandie Univ, Ctr Rech Ions Mat & Photon, ENSICAEN, UNICAEN, CEA, CNRS, CIMAP, F-14000 Caen - France

• Tipo de documento: Artigo Científico
• Fonte: Monthly Notices of the Royal Astronomical Society; v. 494, n. 2, p. 2396-2409, MAY 2020.
• Citações Web of Science: 0

Resumo

The processing of H2O:CO2:CH4 (10:1:1) and H2O:CO2:CH4:NH3 (10:1:1:1) ices at 72 K by oxygen ions was studied in an attempt to simulate the physicochemical effects induced by energetic ions on the surface of Enceladus (or similar cold surfaces in the outer Solar System). The experiments were carried out at the Grand Accelerateur National d'Ions Lourds (GANIL) in Caen/France. The samples were irradiated with 15.7-MeV O5+ at the IRRadiation SUD (IRRSUD) beamline and with 108-key O6+ at the Accelerateurs pour les Recherches avec les Ions de Basses Energies (ARIBE) beamline. The frozen samples were monitored by Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy (4000-650 cm(-1), 2.5-15.4 mu m, at 1 cm(-1) resolution). The identified molecular species formed during irradiation were CO, OCN-,CH3OH, HCN, CN-, H2CO3, HNCO, HCO and CO3. The effective formation cross-sections for the synthesis of new species and the effective molecular destruction cross-sections of the parent species in the experiments with MeV ions were found to be of the order of 10(14)-10(-13) cm(2). For the keV ion experiments, these values were of the order of 10(-16)-10(-15) cm(2). The fluence at which the sample reaches chemical equilibrium and the molecular abundances in this region (equilibrium branching ratios) were estimated. These experiments suggest that the chemical inventory on the surface of Enceladus can be influenced by the incidence of charged particles on to the moon's surface. (AU)

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