Ultraviolet Photoprocessing of Glycine Adsorbed on Various Space-Relevant Minerals

Abstract

The discovery of amino acids such as glycine on meteorites and comets confirms the role of small bodies as transport and delivery vehicles of building blocks of life on Earth and possibly on other planetary bodies of our Solar System. Glycine is quite interesting because it is the simplest of the 20 biogenic amino acids, from which complex organic molecules might have originated in our evolved Solar System. To investigate the possible chemical evolution of this molecule in space, it is important to consider how the interaction with mineral matrices influences its photostability. Indeed, the presence of minerals can mediate the effects of electromagnetic radiation, catalyzing photoreactions, or protecting molecules against degradation. Such interactions are responsible for the preservation/degradation mechanisms of organic molecules in space environments. Laboratory simulations of UV processing may provide key insights into the survival of organic molecules in space environment and rocky surfaces, which is of particular relevance for current missions of sample return from asteroids, such as NASA OSIRIS-REx and JAXA Hayabusa 2, and in particular, upcoming space exploration missions on planetary surfaces, such as ESA-Roscosmos ExoMars 2022 and NASA Mars 2020. In this article, we report a laboratory study of UV irradiation of glycine adsorbed on various space relevant minerals: forsterite, antigorite, spinel, and pyrite. We monitored possible changes of glycine functional groups due to UV irradiation through in situ infrared (IR) spectroscopic analysis. Results show that degradation of glycine occurs with a half-life of 0.5-2 h depending on the mineral substrate. Appearance of new IR bands suggests the occurrence of catalytic reactions mediated by minerals and UV.

Survival of Xanthoria parietina in simulated space conditions: vitality assessment and spectroscopic analysis

“…The Xe lamp is hosted in the Newport Research Arc Lamp Housing 50-500 W (Corazzi et al, 2020). The UV-radiation emitted by the lamp is collimated through an optical system consisting of a first mirror that reflects the radiation coming from the lamp to a grade fused silica collimating condenser lens (type Fused Silica Asphere, f-number f/2.2), which directs UV-radiation towards an optical fibre with an aperture of 800 μm (Poggiali et al, 2020).…”

Dehydration rate of the glycine‐MgSO4·5H2O complex and the stability of glycine expelled from the complex by in situ Raman spectroscopy under Mars‐relevant conditions

“…The observed intensity decreases in the spectra of the irradiated glycine, which can be due to the degradation of glycine, as expected in the presence of UV radiation conditions. [ 3 ] Moreover, the relative intensity between the bands does not undergo substantial variations; thus, the decrease in the intensity of all the bands testify for a mainly molecular desorption due to the UV irradiation. [ 33 ] No deeper analysis has been performed as this is not the aim of the present study because many works have addressed the behavior of glycine under UV radiation.…”

“…Thus, it is widely accepted that minerals can mediate the effects of electromagnetic radiation, catalyzing photoreactions or protecting molecules against degradation. [ 3 ] Therefore, the interactions at the interfaces between minerals and prebiotic molecules (such as amino acids) in nonterrestrial conditions are some of the most discussed topics in astrobiology. [ 4 ] In contrast, the chemical evolution of amino acids such as glycine that are part of a complex under nonterrestrial conditions, which is the subject of this work, is scarcely discussed in the literature, even though the interaction with the metal and the mineral in the complex must be responsible for the conservation/degradation mechanisms of glycine.…”

Degradation of Amino Acids on Mars by UV Irradiation in the Presence of Chloride and Oxychlorine Salts

“…When absorbed on minerals such as forsterite, antigorite, spinel, or pyrite, the half-life of glycine degradation was shown to be between 0.5 -2 h. This relatively rapid degradation of glycine indicates that these minerals on Mars may be involved in photo-Fenton catalytic reactions (Fornaro et al 2018;Poggiali et al 2020). The destructive effect of UV radiation seems to involve more than just the photon energy of the different wavelengths.…”