Photocatalytic oxidation of organic compounds on Mars

Chun, Sandy F. S.; Pang, Kevin D.; Cutts, J. A.; Ajello, J. M.

doi:10.1038/274875a0

Cited by 50 publications

(29 citation statements)

References 14 publications

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“…Indeed, the surface of Mars is considered to be an oxidative environment, and it is hypothesized that one or more oxidants that could destroy organic matter are present in the regolith. This reactivity could be attributed to the presence of catalyzers, one or more inorganic superoxides or peroxides in the martian regolith (Chun et al, 1978;Pang et al, 1982;Yen et al, 2000), H 2 O 2 [recently detected (Clancy et al, 2004;Encrenaz et al, 2004)] diffusion into the regolith (Bullock et al, 1994), or the presence of perchlorates (Hecht et al, 2009). Results of a theoretical study led by Benner et al (2000) with regard to the oxidative action on organic molecules of meteoritic origin in the martian soil show that such compounds should not be entirely oxidized into volatile molecules (i.e., CO 2 and H 2 O).…”

Section: Methodsmentioning

confidence: 99%

“…Yen et al (2000) showed that the interaction of UV radiation with a mineral matrix (labradorite, feldspar) and an oxygen-rich atmosphere could produce one or more inorganic superoxides or peroxides that are able to destroy the organic matter. Chun et al (1978) and Pang et al (1982) showed that TiO 2 catalyzed the oxidation of organics in the presence of oxygen. In our experiment, no rich oxygen atmosphere was present, but the JSC Mars-1 soil contained TiO 2 , as does the martian regolith (Allen et al, 1998).…”

Section: Fig 10mentioning

confidence: 99%

“…Results of our experiments, therefore, imply that a martian soil analogue might play a role in the photocatalytic degradation of organic compounds on Mars. Several laboratory experiments have been conducted to investigate the interaction of UV radiation with a mineral matrix (Chun et al, 1978;Pang et al, 1982;Yen et al, 2000). Yen et al (2000) showed that the interaction of UV radiation with a mineral matrix (labradorite, feldspar) and an oxygen-rich atmosphere could produce one or more inorganic superoxides or peroxides that are able to destroy the organic matter.…”

Section: Fig 10mentioning

confidence: 99%

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UVolution, a Photochemistry Experiment in Low Earth Orbit: Investigation of the Photostability of Carboxylic Acids Exposed to Mars Surface UV Radiation Conditions

et al. 2010

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The detection and identification of organic molecules on Mars are of prime importance to establish the existence of a possible ancient prebiotic chemistry or even a biological activity. To date, however, no complex organic compounds have been detected on Mars. The harsh environmental conditions at the surface of Mars are commonly advocated to explain this nondetection, but few studies have been implemented to test this hypothesis. To investigate the nature, abundance, and stability of organic molecules that could survive under such environmental conditions, we exposed, in low Earth orbit, organic molecules of martian astrobiological relevance to solar UV radiation (>200 nm). The experiment, called UVolution, was flown on board the Biopan ESA module, which was situated outside a Russian Foton automated capsule and exposed to space conditions for 12 days in September 2007. The targeted organic molecules [a-aminoisobutyric acid (AIB), mellitic acid, phthalic acid, and trimesic acid] were exposed with, and without, an analogous martian soil. Here, we present experimental results of the impact of solar UV radiation on the targeted molecules. Our results show that none of the organic molecules studied seemed to be radiotolerant to the solar UV radiation when directly exposed to it. Moreover, the presence of a mineral matrix seemed to increase the photodestruction rate. AIB, mellitic acid, phthalic acid, and trimesic acid should not be considered as primary targets for in situ molecular analyses during future surface missions if samples are only collected from the first centimeters of the top surface layer.

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Section: Methodsmentioning

confidence: 99%

Section: Fig 10mentioning

confidence: 99%

Section: Fig 10mentioning

confidence: 99%

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UVolution, a Photochemistry Experiment in Low Earth Orbit: Investigation of the Photostability of Carboxylic Acids Exposed to Mars Surface UV Radiation Conditions

et al. 2010

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“…The present Martian surface is characterized by high levels of ultraviolet 61 radiation (Cockell et al, 2000), a 1 to 10 mbar CO 2 atmosphere (Owen et and comets (Chun et al, 1978), modeling of the observed disappearance of 74 atmospheric methane (Lefevre and Forget, 2009), and the results from the Viking 75 life detection experiments (Oyama and Berdahl, 1977;Zent and McKay, 1994), 76 strongly suggest that a rapid organic oxidation mechanism is at work in the 77 UV-C due to atmospheric dust and/or CO 2 attenuation (Gunn and Watkins, 1970). Basalt samples were ground in an agate swing mill, 188 sieved to <200 mesh, and baked at 400 °C for 12 hours in ambient atmosphere to 189 sterilize, de-gas and remove organic contaminants from the sample.…”

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confidence: 99%

Extended survival of several organisms and amino acids under simulated martian surface conditions

Johnson

Pratt

Vishnivetskaya

et al. 2011

Icarus

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1Recent orbital and landed missions have provided substantial evidence for 2 ancient liquid water on the Martian surface as well as evidence of more recent 3 sedimentary deposits formed by water and/or ice. These observations raise 4 serious questions regarding an independent origin and evolution of life on Mars. 5Future missions seek to identify signs of extinct Martian biota in the form of 6 biomarkers or morphological characteristics, but the inherent danger of space 7 craft-borne terrestrial life makes the possibility of forward contamination a 8 serious threat not only to the life detection experiments, but also to any extant 9Martian ecosystem. A variety of cold and desiccation-tolerant organisms were 10 exposed to 40 days of simulated Martian surface conditions while embedded 11 within several centimeters of regolith simulant in order to ascertain the 12 plausibility of such organisms' survival as a function of environmental parameters 13 and burial depth. Relevant amino acid biomarkers associated with terrestrial life 14 were also analyzed in order to understand the feasibility of detecting biomarker 15 evidence for previous biological activity. Results indicate that stresses due to 16 desiccation, oxidation, and UV-associated damage were the primary deterrent to 17 organism survival, and that the effect of diurnal temperature variations and 18 reactive atmospheric species were minimal. Organisms with resistance to 19 desiccation and radiation environments showed increased levels of survival after 20the experiment compared to organisms characterized as psychrotolerant. Amino 21 2 acid biomarker analyses indicated the presence of an oxidation mechanism that 22 migrated downward through the samples during the course of the experiment and 23 likely represents the formation of various oxidizing species at mineral surfaces as 24 water vapor diffused through the regolith. Current sterilization protocols may 25 specifically select for organisms best adapted to survival at the Martian surface, 26 namely species that show tolerance to radical-induced oxidative damage and low 27 water activity environments. Additionally, any hypothetical Martian ecosystems 28 may have evolved similar physiological traits that allow sporadic metabolism 29 during periods of increased water activity. 30

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“…We are currently investigating the correlation between the charge density of phyllosilicates and the extent of their possible protective role on the organic molecules, adsorbed on or embedded within them, against the degradation effects of gamma and UV radiation, directly or via the generation of secondary reactive species such as peroxides (Chun et al, 1978;Zent and McKay, 1994). We shall compare the results with possible protective role of other minerals identified on martian soil.…”

Section: Resultsmentioning

confidence: 99%

Correlation Between the Extent of Catalytic Activity and Charge Density of Montmorillonites

et al. 2010

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The clay mineral montmorillonite is a member of the phyllosilicate group of minerals, which has been detected on martian soil. Montmorillonite catalyzes the condensation of activated monomers to form RNA-like oligomers. Extent of catalysis, that is, the yield of oligomers, and the length of the longest oligomer formed in these reactions widely varies with the source of montmorillonite (i.e., the locality where the mineral is mined). This study was undertaken to establish whether there exists a correlation between the extent of catalytic property and the charge density of montmorillonites. Charge density was determined by saturating the montmorillonites with alkyl ammonium cations that contained increasing lengths of alkyl chains, [CH 3 þ , where n ¼ 3-16 and 18, and then measuring d (001) , interlayer spacing of the resulting montmorillonite-alkyl ammoniummontmorillonite complex by X-ray diffractometry (XRD).Results demonstrate that catalytic activity of montmorillonites with lower charge density is superior to that of higher charge density montmorillonite. They produce longer oligomers that contain 9 to 10 monomer units, while montmorillonite with high charge density catalyzes the formation of oligomers that contain only 4 monomer units.The charge density of montmorillonites can also be calculated from the chemical composition if elemental analysis data of the pure mineral are available. In the next mission to Mars, CheMin (Chemistry and Mineralogy), a combined X-ray diffraction/X-ray fluorescence instrument, will provide information on the mineralogical and elemental analysis of the samples. Possible significance of these results for planning the future missions to Mars for the search of organic compounds and extinct or extant life is discussed.

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Photocatalytic oxidation of organic compounds on Mars

Cited by 50 publications

References 14 publications

UVolution, a Photochemistry Experiment in Low Earth Orbit: Investigation of the Photostability of Carboxylic Acids Exposed to Mars Surface UV Radiation Conditions

UVolution, a Photochemistry Experiment in Low Earth Orbit: Investigation of the Photostability of Carboxylic Acids Exposed to Mars Surface UV Radiation Conditions

Extended survival of several organisms and amino acids under simulated martian surface conditions

Correlation Between the Extent of Catalytic Activity and Charge Density of Montmorillonites

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