Phosphorus is an essential element for life on Earth and can be found in its fully oxidized P(V) state in biological compounds such as DNA/RNA, ATP, and phospholipids. However, the ultimate source of prebiotic phosphorus remains elusive because of the poor bioavailability of P(V)-phosphate (PO43-) minerals. A proposed solution to this “phosphorus problem” utilizes reduced oxidation state phosphorus compounds, in particular the P(III) oxidation state compounds derived from phosphorous acid, H3PO3. Of particular interest are the alkylphosphonic acids, which are the alkylated products of phosphorous acid, as these are the only phosphorus-containing organic compounds discovered in the Murchison meteorite. These alkylphosphonic acids represent a reactive, bioavailable, and exogenous source of prebiotic phosphorus, and this present study investigates the role of phosphine (PH3) as a phosphorus-source for compounds such as the alkylphosphonic acids. Phosphine has been detected in the circumstellar envelop of IRC +10216 and exists in the atmospheres of Jupiter and Saturn; moreover, the phosphorus detected in the comet 67P/Churyumov-Gerasimenko has been speculated to arise from phosphine. To investigate condensed-phase phosphine chemistry, irradiated ices of phosphine, water (H2O), carbon dioxide (CO2), and methane (CH4) were studied using Fourier-transform infrared spectroscopy (FTIR), quadrupole mass spectrometry (QMS), and a more sensitive reflectron time-of-flight mass spectrometer (ReTOF-MS) that allows for tunable photoionization. These irradiated ices, which were studied under ultra-high vacuum conditions and cryogenic temperatures, produced residues of larger and less-volatile products that were analyzed ex-situ using secondary-ion mass spectrometry (SIMS) and chromatography methods. The results of this study advance the knowledge of phosphorus chemistry in interstellar ices and provide a possible explanation toward the formation of alkylphosphonic acids.

Investigating the formation of alkylphosphonic acids in phosphine ices

253rd National Meeting (2017)

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