Carbon Isotopic Composition of CO2, Evolved During Perchlorate-Induced Reactions in Mars Analog Materials: Interpreting SAM/MSL Rocknest Data

The Sample Analysis at Mars (SAM) Instrument Suite on the Mars Science Laboratory (MSL) Rover Curiosity made its first solid sample evolved gas analysis of unconsolidated material at aeolian bedform Rocknest in Gale Crater. The magnitude of O2 evolved in each run as well as the chlorinated hydrocarbons detected by SAM gas chromatograph/ mass spectrometer (GCMS) [1] suggest a chlorinated oxidant such as perchlorate in Rocknest materials [2]. Perchlorate induced combustion of organics present in the sample would contribute to the CO2 volatile inventory, possibly overlapping with CO2 from inorganic sources. The resulting carbon and oxygen isotopic composition of CO2 sent to the Tunable Laser Spectrometer (TLS) for analysis would represent mixed sources. This work was undertaken to better understand a) how well the carbon isotopic composition ( 13C) of CO2 from partially combusted products represents their source and b) how the 13C of combusted products can be deconvolved from other carbon sources such as thermal decomposition of carbonate.