Radiation-Driven Formation of Reactive Oxygen Species in Oxychlorine-Containing Mars Surface Analogues

Abstract

The present study demonstrates that γ-radiolyzed perchlorate-containing Mars soil salt analogues (in a CO atmosphere) generate upon HO wetting the reactive oxygen species (ROS) superoxide radical (O), hydrogen peroxide (HO), and hydroxyl radicals (OH). This study also validates that analogue radiolysis forms oxychlorine species that, in turn, can UV-photolyze to OH upon UV photolysis. This investigation was made possible by the development of a new assay for inorganic-origin O and HO determination and by the modification of a previous assay for soil OH. Results show that radiolyzed Mg(ClO) generates HO and OH; and when included as part of a mixture analogous to the salt composition of samples analyzed at the Mars Phoenix site, the analogue generated O, HO, and OH, withOH levels 150-fold higher than in the radiolyzed Mg(ClO) samples. Radiolyzed Mars Phoenix site salt analogue that did not contain Mg(ClO) generated only OH also at 150-fold higher concentration than Mg(ClO) alone. Additionally, UV photolysis of the perchlorate γ radiolysis product chlorite (ClO) generated the oxychlorine products trihalide (Cl), chlorine dioxide (ClO), and hypochlorite (ClO), with the formation of OH by UV photolysis of ClO. While the generation of ROS may have contributed in part to CO production in the Viking Labeled Release (LR) experiment and O (g) release in the Viking Gas Exchange (GEx) experiment, our results indicate that they are not likely to be the major contributor to the LR and GEx results. However, due to their highly reactive nature, they are expected to play a significant role in the alteration of organics on Mars. Additionally, experiments with hypochlorite show that the thermal stability of NaClO is in the range of the thermal stability observed for thermally liable oxidant responsible for the Viking LR results. Key Words: Mars-Oxygen-Salts-Radiation-Habitability. Astrobiology 17, 319-336.

Reactive Oxygen Species Penetrate Persister Cell Membranes of Escherichia coli for Effective Cell Killing

“…However, despite the complete inhibition of UV irradiation toward the cell sample, the levels of surviving E. coli were gradually decreased. ROS are produced by UV irradiation to oxygen and water in the atmosphere (de Jager et al, 2017 ; Georgiou et al, 2017 ). In the ESR results, hydroxyl radicals were detected at high concentrations than in the NC.…”

Molecular biomarkers in the subsurface of the Salar Grande (Atacama, Chile) evaporitic deposits

“…Similarities between the Atacama Desert (Chile) and certain current Mars regions include extreme and prolonged aridity (Dunai et al 2005), highly oxidizing chemistry, and intense UV radiation that promote high rates of oxidant production in the soil (Quinn et al 2013;Georgiou et al 2015Georgiou et al , 2017) and a very low water activity (Navarro-González et al 2003;Davila et al 2008). The Mars halide deposits correspond to 5-20 m thick materials that, similar to the Atacama materials, were formed from the evaporation of isolated water masses, which were eventually supplied by ground aquifers (Osterloo et al 2010).…”

Ionizing Radiation as a Source of Oxidative Stress—The Protective Role of Melatonin and Vitamin D

“…•− ) and hydroxyl radical (OH • ) [46,47]. The hydroxyl radical is the most dangerous for tissues due to its high reactivity and the ability to oxidize many cell components, such as lipids, proteins, carbohydrates and deoxyribonucleic acids [48,49].…”

“…ROS, which are products of excitation and one-, two- and three-electron reduction of the oxygen molecule, are characterized by much greater reactivity than the oxygen in the ground state [ 45 , 46 ]. ROS are a broad concept, including ions, atoms, as well as molecules and radicals such as hydrogen peroxide (H 2 O 2 ), singlet oxygen ( 1 O 2 ), superoxide anion radical (O 2 •− ) and hydroxyl radical (OH • ) [ 46 , 47 ]. The hydroxyl radical is the most dangerous for tissues due to its high reactivity and the ability to oxidize many cell components, such as lipids, proteins, carbohydrates and deoxyribonucleic acids [ 48 , 49 ].…”