The thermal reactivity of a water-dominated cometary ice analog containing H2CO and NH3 is investigated by means of Fourier transform infrared spectroscopy, mass spectrometry, and B3LYP calculations. Three products are characterized by these techniques: aminomethanol (NH 2CH2OH), methyleneglycol (HOCH2OH), and polyoxymethylene (POM, HO-(CH2-O)n -H). Their formation strongly depends on the initial NH3/H2CO ratio. In addition, the influence of the initial ice composition on the thermal stability of POM has also been investigated. It is shown that POM formed during warming of the ices consists of short-chain polymers (i.e., oligomers of formaldehyde HO-(CH2-O)n -H, n < 5), which are volatile at temperatures higher than 200 K. This suggests that gas-phase detection by the ROSINA instrument on board the Rosetta mission would be the most appropriate method to detect POM. Moreover, the mass spectra presented in this work might help in the interpretation of data that will be recorded by this instrument. Finally, a new scenario to explain the distributed source of formaldehyde observed in comets is discussed. © 2014. The American Astronomical Society. All rights reserved..
- comets: general
- ISM: molecules
- methods: laboratory: molecular
- molecular processes