Identification of chlorobenzene in the Viking gas chromatograph-mass spectrometer data sets: Reanalysis of Viking mission data consistent with aromatic organic compounds on Mars
Résumé
The twin 1976 Viking landers (VL-1/VL-2) performed the first in situ search for organic molecules on the martian surface. Each lander carried a pyrolysis-gas chromatograph mass spectrometer (GCMS), which was used to search for organics in regolith samples excavated with a robotic arm (Biemann et al. (1976)). 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 (Freissinet et al. (2015)), we reexamined the original Viking GCMS data sets. We performed directed research of key molecules identified with the SAM instrument; attributed to organic matter indigenous to Mars. Using this approach, 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). We considered possible sources of carbon that may have produced the chlorobenzene signal, by reaction with perchlorate during pyrolysis. 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. Through this work we have demonstrated that the Viking GCMS experiment could have detected organic materials indigenous to Mars for the first time