Photoprocessing of formamide ice: route towards prebiotic chemistry in space

Abstract

Aims. Formamide (HCONH 2 ) is the simplest molecule containing the peptide bond first detected in the gas phase in Orion-KL and SgrB 2 . In recent years, it has been observed in high temperature regions such as hot corinos, where thermal desorption is responsible for the sublimation of frozen mantles into the gas phase. The interpretation of observations can benefit from information gathered in the laboratory, where it is possible to simulate the thermal desorption process and to study formamide under simulated space conditions such as UV irradiation. Methods. Here, two laboratory analyses are reported: we studied formamide photo-stability under UV irradiation when it is adsorbed by space relevant minerals at 63 K and in the vacuum regime. We also investigated temperature programmed desorption of pure formamide ice in the presence of TiO 2 dust before and after UV irradiation. Results. Through these analyses, the effects of UV degradation and the interaction between formamide and different minerals are compared. We find that silicates, both hydrates and anhydrates, offer molecules a higher level of protection from UV degradation than mineral oxides. The desorption temperature found for pure formamide is 220 K. The desorption temperature increases to 250 K when the formamide desorbs from the surface of TiO 2 grains. Conclusions. Through the experiments outlined here, it is possible to follow the desorption of formamide and its fragments, simulate the desorption process in star forming regions and hot corinos, and constrain parameters such as the thermal desorption temperature of formamide and its fragments and the binding energies involved. Our results offer support to observational data and improve our understanding of the role of the grain surface in enriching the chemistry in space.

2-aminooxazole in Astrophysical Environments: IR Spectra and Destruction Cross Sections for Energetic Processing

“…A larger wavelength, UV radiation, at 285 nm, provided by a Xe lamp coupled to a monocromator, was used by Puletti (2014) to process glycoaldehyde (HCOCH2OH) ice. A recent work by Corazzi et al (Corazzi et al, 2020) investigates the photo destruction of formamide (HCONH2) ice deposited at 63 K on top of different minerals, with a Xenon lamp in the 230-300 nm range. For the larger wavelengths (≈ 260-280 nm) employed in the last two works, the destruction cross sections found are in the 10 -20 cm 2 range.…”

Destruction route of solid-state formamide by thermal H atoms

“…(b) Photons from UV-enhanced xenon lamp. (c) Cross-section of NH 2 CHO deposited on oxides and minerals (Corazzi et al 2020). (d) Corresponds to 10 eV photons (Mathis et al 1983).…”

“…Very recently, Corazzi et al (2020) performed a laboratory experiment on UV photoprocessing of pure NH 2 CHO ice. They did not find a significant degradation of NH 2 CHO, consequently the destruction cross-section could not be evaluated.…”

“…For example, under electron and Ly-α irradiation of NH 2 CHO, OCN − and CO were obtained (Dawley et al 2014). A pure NH 2 CHO ice film does not show significant degradation upon exposure to a UV-enhanced xenon lamp, whereas in the presence of oxide minerals TiO 2 and MgAl 2 O 4 , a gradual degradation was observed (Corazzi et al 2020). Also, no reaction occurred between NH 2 CHO ice and a hydrogen atom (Noble et al 2015).…”

From gaseous HCN to nucleobases at the cosmic silicate dust surface: an experimental insight into the onset of prebiotic chemistry in space

“…It is finally noticeable that most of the experiments in this field are performed by thermal processing (T c 300 K) or UV/proton irradiation as an energetic input in order to simulate the harsh astrophysical context. [19][20][21][22][23] In contrast, studies focused on the role played by mineral surfaces in adsorbing and concentrating gas phase HCN and in catalysing its transformation into products of prebiotic relevance without external energy inputs are lacking. Aiming to contribute to fill this gap, we have studied the interaction of pure HCN with the surface of a synthetic Mg-silicate with end-member stoichiometry (Mg 2 SiO 4 ) in amorphous (AMS) and crystalline (CMS or forsterite) forms, assumed as laboratory models of cosmic silicate core dust particles.…”