title: The limitations on organic detection in Mars-like soils by thermal volatilization-gas chromatography-MS and their implications for the Viking results.
abstract: The failure of Viking Lander thermal volatilization (TV) (without or with thermal degradation)-gas chromatography (GC)-MS experiments to detect organics suggests chemical rather than biological interpretations for the reactivity of the martian soil. Here, we report that TV-GC-MS may be blind to low levels of organics on Mars. A comparison between TV-GC-MS and total organics has been conducted for a variety of Mars analog soils. In the Antarctic Dry Valleys and the Atacama and Libyan Deserts we find 10-90 mug of refractory or graphitic carbon per gram of soil, which would have been undetectable by the Viking TV-GC-MS. In iron-containing soils (jarosites from Rio Tinto and Panoche Valley) and the Mars simulant (palogonite), oxidation of the organic material to carbon dioxide (CO(2)) by iron oxides and/or their salts drastically attenuates the detection of organics. The release of 50-700 ppm of CO(2) by TV-GC-MS in the Viking analysis may indicate that an oxidation of organic material took place. Therefore, the martian surface could have several orders of magnitude more organics than the stated Viking detection limit. Because of the simplicity of sample handling, TV-GC-MS is still considered the standard method for organic detection on future Mars missions. We suggest that the design of future organic instruments for Mars should include other methods to be able to detect extinct and/or extant life.
authors.affiliation: Laboratorio de Química de Plasmas y Estudios Planetarios, Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, P.O. Box 70-543, 04510 México D.F., Mexico. navarro@nucleares.unam.mx
authors.forename: Rafael
authors.initials: R
authors.lastname: Navarro-González
authors.forename: Karina F
authors.initials: KF
authors.lastname: Navarro
authors.forename: José
authors.initials: J
authors.lastname: de la Rosa
authors.forename: Enrique
authors.initials: E
authors.lastname: Iñiguez
authors.forename: Paola
authors.initials: P
authors.lastname: Molina
authors.forename: Luis D
authors.initials: LD
authors.lastname: Miranda
authors.forename: Pedro
authors.initials: P
authors.lastname: Morales
authors.forename: Edith
authors.initials: E
authors.lastname: Cienfuegos
authors.forename: Patrice
authors.initials: P
authors.lastname: Coll
authors.forename: François
authors.initials: F
authors.lastname: Raulin
authors.forename: Ricardo
authors.initials: R
authors.lastname: Amils
authors.forename: Christopher P
authors.initials: CP
authors.lastname: McKay
mesh_terms: D002244:Carbon / Q000737:chemistry; D002245:Carbon Dioxide / Q000737:chemistry; D002384:Catalysis; D002849:Chromatography, Gas; D018535:Mars; D013058:Mass Spectrometry; D009930:Organic Chemicals / Q000032:analysis* / Q000737:chemistry*; D010084:Oxidation-Reduction; D012987:Soil / Q000032:analysis*; D013696:Temperature; D013816:Thermodynamics; D014835:Volatilization
chemical_list: D009930:Organic Chemicals; D012987:Soil; D002245:Carbon Dioxide; D002244:Carbon