Phosphorus Monoxide in Cometary Volatiles

Phosphorous-bearing compounds have been observed in comets and meteorites as well as planets, ISM, and other regions of space. They have been detected in the dust component of comets 1P/Halley and 81P/Wild 2, and in the gas phase of 67P/Churyumov-Gerasimenko (atomic P and PO). A gas dynamics model of cometary comae with chemical kinetics (Suisei) has been adapted to study this problem. Using newly calculated photo rates for PO, results from this quantitative study of P-bearing molecules in cometary comae are presented. Reaction pathways of gas-phase and photolytic chemistry for simple P-bearing molecules, including PO and PH₃, are identified. Since phosphorus is a key element in all living organisms, these results may be important for prebiotic chemistry, possibly shedding light on understanding prebiotic to biotic evolution of life on early Earth and the role that comets played.

Acknowledgments: We greatly appreciate support from FAPESP (Grant No. 2015/03176-8, Brazil) and the NSF Planetary Astronomy Program (Grant No. 0908529, USA).