Identification of chlorobenzene in the Viking gas chromatograph-mass spectrometer data sets: Reanalysis of Viking mission data consistent with aromatic organic compounds on Mars - INSU - Institut national des sciences de l'Univers Accéder directement au contenu
Communication Dans Un Congrès Année : 2018

Identification of chlorobenzene in the Viking gas chromatograph-mass spectrometer data sets: Reanalysis of Viking mission data consistent with aromatic organic compounds on Mars

Melissa Guzman
  • Fonction : Auteur
  • PersonId : 1033337
Cyril Szopa
Caroline Freissinet
Alfonso F. Davila

Résumé

The twin 1976 Viking landers (VL-1 and VL-2) performed the first in situ search for organic compounds on the martian surface. Each lander carried a pyrolysis-gas chromatograph mass spectrometer (pyr-GCMS), which were used to search for organic molecules in regolith samples excavated with a robotic arm [1]. Chloromethane was detected by VL-1 at levels of 15 parts per billion (ppb) and dichloromethane was detected by VL-2 at levels of 2-40 ppb [2]. Both chlorinated hydrocarbons were attributed to either terrestrial contamination resulting from the pre-flight use of chlorinated cleaning-solvents, or from the reaction of absorbed traces of methanol and HCl [2]. After martian perchlorate was discovered by the Wet Chemistry Laboratory on the 2008 Phoenix lander [3], Navarro-Gonzalez et al. [4] suggested that parts per million (ppm) levels of indigenous martian organics may have provided the carbon source for the reaction with perchlorate in the Viking GCMS ovens that resulted in the formation of the detected level of chlorinated organics. Motivated by the recent detection of chlorobenzene by the Sample Analysis at Mars (SAM) instrument suite on the Curiosity rover, and the identification of its carbon source as indigenous to Mars [5], we reexamined the original, microfilm preserved, Viking pyr-GCMS data sets. Here we show evidence for the presence of chlorobenzene in VL-2 data at levels corresponding to 0.08-1.0 ppb (relative to sample mass), in runs when the sample was heated respectively to 350°C and 500°C. We considered possible sources of carbon that may have produced the chlorobenzene signal, by reaction with perchlorate during pyrolysis, including potential indigenous martian organics and previously unreported instrument contamination. We conclude that the chlorobenzene signal measured by VL-2 originated from martian chlorine sources, and its carbon source is consistent with a martian origin, though a carbon source contribution from the instrument background cannot yet be ruled out. Through this work we have demonstrated that the Viking pyr-GCMS experiment may have detected organic materials indigenous to Mars' surface for the first time, almost forty years before the Curiosity rover's SAM experiment detected indigenous martian organics.
Fichier non déposé

Dates et versions

insu-04501872 , version 1 (12-03-2024)

Identifiants

Citer

Melissa Guzman, Rafael Navarro-Gonzalez, Cyril Szopa, Christopher P. Mckay, Richard C. Quinn, et al.. Identification of chlorobenzene in the Viking gas chromatograph-mass spectrometer data sets: Reanalysis of Viking mission data consistent with aromatic organic compounds on Mars. 42nd COSPAR Scientific Assembly, Jul 2018, Pasadena, United States. pp.Abstract id. B4.1-41-18. ⟨insu-04501872⟩
1 Consultations
0 Téléchargements

Partager

Gmail Facebook X LinkedIn More