Effect of Nontronite Smectite Clay on the Chemical Evolution of Several Organic Molecules under Simulated Martian Surface Ultraviolet Radiation Conditions

Poch, Olivier; Jaber, Maguy; Stalport, Fabien; Nowak, Sophie; Georgelin, Thomas; Lambert, Jean-Francois; Szopa, Cyril; Coll, Patrice (2015). Effect of Nontronite Smectite Clay on the Chemical Evolution of Several Organic Molecules under Simulated Martian Surface Ultraviolet Radiation Conditions. Astrobiology, 15(3), pp. 221-237. Mary Ann Liebert 10.1089/ast.2014.1230

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Most of the phyllosilicates detected at the surface of Mars today are probably remnants of ancient environments that sustained long-term bodies of liquid water at the surface or subsurface and were possibly favorable for the emergence of life. Consequently, phyllosilicates have become the main mineral target in the search for organics on Mars. But are phyllosilicates efficient at preserving organic molecules under current environmental conditions at the surface of Mars? We monitored the qualitative and quantitative evolutions of glycine, urea, and adenine in interaction with the Fe3+-smectite clay nontronite, one of the most abundant phyllosilicates present at the surface of Mars, under simulated martian surface ultraviolet light (190-400 nm), mean temperature (218 +/- 2 K), and pressure (6 +/- 1 mbar) in a laboratory simulation setup. We tested organic-rich samples that were representative of the evaporation of a small, warm pond of liquid water containing a high concentration of organics. For each molecule, we observed how the nontronite influences its quantum efficiency of photodecomposition and the nature of its solid evolution products. The results reveal a pronounced photoprotective effect of nontronite on the evolution of glycine and adenine; their efficiencies of photodecomposition were reduced by a factor of 5 when mixed at a concentration of 2.6x10(-2) mol of molecules per gram of nontronite. Moreover, when the amount of nontronite in the sample of glycine was increased by a factor of 2, the gain of photoprotection was multiplied by a factor of 5. This indicates that the photoprotection provided by the nontronite is not a purely mechanical shielding effect but is also due to stabilizing interactions. No new evolution product was firmly identified, but the results obtained with urea suggest a particular reactivity in the presence of nontronite, leading to an increase of its dissociation rate. Key Words: Martian surface-Organic chemistry-Photochemistry-Astrochemistry-Nontronite-Phyllosilicates. Astrobiology 15, 221-237.

Item Type:

Journal Article (Original Article)

Division/Institute:

10 Strategic Research Centers > Center for Space and Habitability (CSH)
08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences

UniBE Contributor:

Poch, Olivier

Subjects:

500 Science > 520 Astronomy
500 Science > 530 Physics

ISSN:

1531-1074

Publisher:

Mary Ann Liebert

Language:

English

Submitter:

Katharina Weyeneth-Moser

Date Deposited:

17 Jun 2016 14:23

Last Modified:

28 Jun 2016 08:16

Publisher DOI:

10.1089/ast.2014.1230

Web of Science ID:

000350804100004

BORIS DOI:

10.7892/boris.81948

URI:

https://boris.unibe.ch/id/eprint/81948

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