Comment on “Reanalysis of the Viking results suggests perchlorate and organics at midlatitudes on Mars”by Rafael Navarro-González et al.

摘要

The reanalysis of the Viking 1976 data by NavarroGonzález et al. [2010, 2011] asserts that the finding of chloromethane in one Martian soil sample at landing site 1 (VL-1) and dichloromethane in both samples collected at site 2 (VL-2), originally attributed to terrestrial contamination [Biemann et al., 1976, 1977], indicates instead the presence of perchlorate and organic carbon. This conclusion is based on experiments with Atacama Desert soil in the presence of added 1 w% magnesium perchlorate and in the absence of added perchlorate. With added perchlorate chloromethane and dichloromethane are simultaneously and exclusively produced at temperatures of ≥350°C. This is not consistent with the Viking results. Kinetic modeling by Navarro-González et al. [2010] assumes that these two chlorohydrocarbons are produced by reaction of chlorine derived from the thermal decomposition of the perchlorate with methane even though the latter is not detected when the soil sample is heated without perchlorate. The absence of the equally likely production of chlorinated aromatic molecules does not support the conclusions presented.