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Article Dans Une Revue Monthly Notices of the Royal Astronomical Society Année : 2020

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

Résumé

The processing of H 2 O:CO 2 :CH 4 (10:1:1) and H 2 O:CO 2 :CH 4 :NH 3 (10:1:1:1) ices at 72 K by oxygen ions was studied in attempt to simulate the physicochemical effects induced by energetic ions on Enceladus surface (or similar cold surfaces in the outer Solar System). The experiments were carried out at GANIL (Grand Accélérateur National d'ions Lourds) in Caen/France. The samples were irradiated with 15.7 MeV O 5+ at the IRRSUD beamline and with 108 keV O 6+ at the ARIBE beamline. The frozen samples were monitored by FTIR Spectroscopy (4000-650 cm-1 , 2.5-15.4 μm, at 1 cm-1 resolution). The identified molecular species formed during irradiation were: CO, OCN − , CH 3 OH, HCN, CN − ,H 2 CO 3 , HNCO, HCO and CO 3. 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 ions 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 Enceladus surface can be influenced by the incidence of charged particles onto the moon's surface.
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Dates et versions

hal-03033453 , version 1 (01-12-2020)

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M G Rachid, S Pilling, W R M Rocha, A Agnihotri, H Rothard, et al.. Processing of 72-K water-rich ices by keV and MeV oxygen ions: implications for the Saturnian moon Enceladus. Monthly Notices of the Royal Astronomical Society, 2020, 494 (2), pp.2396-2409. ⟨10.1093/mnras/staa778⟩. ⟨hal-03033453⟩
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