Photochemistry and desorption induced by X-rays in water rich astrophysical ice analogs: implications for the moon Enceladus and other frozen space environments

Author(s)

Pilling, S. ^{[1, 2]} ; Rocha, W. R. M. ^[3] ; Freitas, F. M. ^[1] ; da Silva, P. A. ^{[1, 4]}

Affiliation

^[1] Univ Vale Paraiba UNIVAP, Lab Astroquim & Astrobiol LASA, Av Shishima Hifumi 2911, Sao Jose Dos Campos, SP - Brazil

^[2] DCTA, ITA, Dept Fis, BR-12228900 Sao Jose Dos Campos, SP - Brazil

^[3] Univ Copenhagen, Niels Bohr Inst Ctr Star & Planet Format, Oster Voldgade 5-7, DK-1350 Copenhagen K - Denmark

^[4] Univ Sao Paulo EEL, Escola Engn Lorena, Estr Municipal Campinho S-N, BR-12602810 Lorena, SP - Brazil

• Document type: Journal article
• Source: RSC ADVANCES; v. 9, n. 49, p. 28823-28840, SEP 12 2019.
• Web of Science Citations: 0

Abstract

Soft X-rays are an important agent for chemical processing in the Solar System and in the interstellar medium. The photolysis and photodesorption processes of H2O-rich ices triggered by soft X-rays was, experimentally, addressed in this paper. The experiments were performed at the Brazilian synchrotron facility LNLS/CNPEN employing broadband radiation (from 6 to 2000 eV; mainly soft X-rays and a small fraction of VUV) in solid samples at temperatures of 20 and 80 K. The icy samples were monitored by infrared spectroscopy. We determined the effective destruction cross section (in the order 10(-18) cm(2)) as well as the formation cross section for the new species produced after the irradiation. Among them, we list OCN-, CO, CO3, CH3OH, H2O2, HCOO-, NH4+, HCONH2 and CH3HCO, mostly formed in the experiment at 80 K. The chemical equilibrium stage was characterized and molecular abundances were quantified. In addition, we discuss a methodology to estimate the amount of unknown species in the ice produced by photolysis. The samples reach chemical equilibrium at fluences around 2-3 x 10(18) cm(-2). Timescales for reaching chemical equilibrium in space environments illuminated by X-rays were given, as well as the desorption yields induced by X-rays. The astrophysical implication on the surface chemistry and desorption processes at the moon Enceladus are provided. (AU)

• FAPESP's process: 15/10492-3 - Study about the chemical evolution of astrophysical ices in the vicinity of young stellar objects employing experimental data in the infrared and computational modeling codes
• Grantee: Will Robson Monteiro Rocha
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 09/18304-0 - Synthesis and degradation of prebiotic molecular species at planetary atmospheres, comets and interstellar ice analogs
• Grantee: Sergio Pilling Guapyassu de Oliveira
• Support Opportunities: Research Grants - Young Investigators Grants
• FAPESP's process: 13/07657-5 - Computational modeling of circumstellar environment of protostars by employing data of bombarded ices with cosmic rays simulated in laboratory.
• Grantee: Will Robson Monteiro Rocha
• Support Opportunities: Scholarships in Brazil - Doctorate