Viking Labeled Release Biology Experiment: Interim Results

Levin, Gilbert V.; Straat, Patricia Ann

doi:10.1126/science.194.4271.1322

Cited by 139 publications

(70 citation statements)

References 9 publications

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“…Samples of soil from the top 10 cm of the Martian surface released dioxygen when exposed to humidity (1). At least one compound in a set of radiolabeled organic compounds (formate, D,L-lactate, glycolate, glycine, and D,Lalanine) released radiolabeled carbon dioxide when placed in aqueous solution on the Martian surface, evidently via oxidative processes (2). Both results were initially thought to indicate the presence of life.…”

Section: Gc-ms On the Viking 1976mentioning

confidence: 60%

The missing organic molecules on Mars

Benner

Devine

Matveeva

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

377

350

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GC-MS on the Viking 1976Mars missions did not detect organic molecules on the Martian surface, even those expected from meteorite bombardment. This result suggested that the Martian regolith might hold a potent oxidant that converts all organic molecules to carbon dioxide rapidly relative to the rate at which they arrive. This conclusion is influencing the design of Mars missions. We reexamine this conclusion in light of what is known about the oxidation of organic compounds generally and the nature of organics likely to come to Mars via meteorite. We conclude that nonvolatile salts of benzenecarboxylic acids, and perhaps oxalic and acetic acid, should be metastable intermediates of meteoritic organics under oxidizing conditions. Salts of these organic acids would have been largely invisible to GC-MS. Experiments show that one of these, benzenehexacarboxylic acid (mellitic acid), is generated by oxidation of organic matter known to come to Mars, is rather stable to further oxidation, and would not have been easily detected by the Viking experiments. Approximately 2 kg of meteorite-derived mellitic acid may have been generated per m 2 of Martian surface over 3 billion years. How much remains depends on decomposition rates under Martian conditions. As available data do not require that the surface of Mars be very strongly oxidizing, some organic molecules might be found near the surface of Mars, perhaps in amounts sufficient to be a resource. Missions should seek these and recognize that these complicate the search for organics from entirely hypothetical Martian life.Viking ͉ organic compounds ͉ exobiology ͉ astrobiology

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Section: Gc-ms On the Viking 1976mentioning

confidence: 60%

The missing organic molecules on Mars

Benner

Devine

Matveeva

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

377

350

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“…In the absence of a life detection experiment on Philae, similar to the 1976 Mars Viking Labelled Release Experiment [4], we can only hope for indirect pointers to the presence of microbial life on Comet 67P/C-G. In this communication we show that indications of biological activity are already available from early results of the Rosetta mission.…”

Section: Introductionmentioning

confidence: 74%

“…When first imaged at a distance of 3.7 AU from the sun, the surface temperature of Comet 67P/C-G averaged 205 K (VIRTIS IR imaging), then had peaks of 230 K at 3.5AU [4]. The surface temperature of Comet Hale-Bopp when it was at 6.5 AU would on normal scaling have been ~155 K. In neither case can the presence of liquid water at the surface be justified.…”

Section: Activity Of Comet 67p/c-g At Rosetta Encountermentioning

confidence: 99%

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Rosetta Studies of Comet 67P/Churyumov–Gerasimenko: Prospects for Establishing Cometary Biology

Nc¹,

Wainwright²,

Smith³

et al. 2015

Astrobiol Outreach

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We discuss a wide range of data emerging from the Rosetta Mission that all point indirectly to biological activity in Comet 67P/Churyumov-Gerasimenko. The existence of cracks and fissures on a smooth surface terrain apparently resealed, as well as early outgassing activity are consistent with the existence of subsurface lakes in which biological activity builds up high pressures of volatile gases that sporadically ruptures a frozen icy crust. While microorganisms probably require liquid water bodies for their early colonising of a comet, they can inhabit cracks in ice and sub-crustal snow, especially if they contain antifreeze salts and biopolymers. Some organisms metabolise at temperatures as low as 230 K, explaining the coma of Comet 97P out at 3.9AU and our prediction is that they would become increasingly active in the near-surface layers as the comet approaches its 1.3 AU perihelion. The detection of an overwhelming abundance of complex organic molecules at the surface by Philae and through IR imaging by the Rosetta orbiter is most significant.

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“…In summary, the results of the first six LR analyses of the Mars surface material (Levin & Straat 1976) have demonstrated the following : (1) Addition of nutrient to surface material resulted in a rapid evolution of counts until a level of 10 000 to 15 000 counts per minute is achieved, possibly corresponding to utilization of only one of the seven carbon substrates offered (namely, formate, glycolate, glycine, D-and L-alanine, D-and L-lactate, uniformly labelled with 14 C).…”

mentioning

confidence: 99%

Life detection experiments of the Viking Mission on Mars can be best interpreted with a Fenton oxidation reaction composed of H₂O₂ and Fe²⁺ and iron-catalysed decomposition of H₂O₂

Apak

2008

International Journal of Astrobiology

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: The findings of the life detection experiments carried out during the Viking mission to Mars were reinterpreted with a chemical hypothesis. The labelled release (LR), pyrolytic release (PR) and gas exchange (GEx) experiments were interpreted with Fenton chemistry. Oxygen and carbon dioxide evolution from Martian soil upon wetting and nutrient addition could be attributed to competition reactions between the Fenton-type oxidation of organic nutrients with the aqueous (hydrogen peroxide+Fe(II)) combination and the iron-catalysed decomposition of hydrogen peroxide. A substantial evolution of radioactive gas upon addition of labelled organic nutrient solution to soil, whereas the ceasing of this gas with a heat treated sample in the LR experiments, was attributed to Fenton oxidation and hydrogen peroxide thermal decomposition, respectively. The peculiar kinetics of LR and PR experiments -that cannot be fully explained by other chemical or biochemical scenarios -were easily explained with this new hypothesis, i.e. limitation of the Fenton reaction may arise from the depletion of reactants, the build-up of ferric hydroxide on soil and excessive scavenging by the organic nutrients of the generated hydroxyl radicals. Reabsorption or adsorption of evolved or introduced CO 2 may involve the formation of carbonate compounds (e.g., magnesium carbonate and bicarbonate) on the surface of alkalinized soil as a result of the Fenton reaction.A critical evaluation of the recent biological hypothesis assuming the utilization of a hydrogen peroxide-water intracellular fluid by putative organisms (Houtkooper & Schulze-Makuch 2007) is also made.

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Viking Labeled Release Biology Experiment: Interim Results

Cited by 139 publications

References 9 publications

The missing organic molecules on Mars

The missing organic molecules on Mars

Rosetta Studies of Comet 67P/Churyumov–Gerasimenko: Prospects for Establishing Cometary Biology

Life detection experiments of the Viking Mission on Mars can be best interpreted with a Fenton oxidation reaction composed of H₂O₂ and Fe²⁺ and iron-catalysed decomposition of H₂O₂

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Viking Labeled Release Biology Experiment: Interim Results

Cited by 139 publications

References 9 publications

The missing organic molecules on Mars

The missing organic molecules on Mars

Rosetta Studies of Comet 67P/Churyumov–Gerasimenko: Prospects for Establishing Cometary Biology

Life detection experiments of the Viking Mission on Mars can be best interpreted with a Fenton oxidation reaction composed of H2O2 and Fe2+ and iron-catalysed decomposition of H2O2

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Life detection experiments of the Viking Mission on Mars can be best interpreted with a Fenton oxidation reaction composed of H₂O₂ and Fe²⁺ and iron-catalysed decomposition of H₂O₂