A thermo-acoustic gas sensor array for photochemically critical species in the martian atmosphere

We describe the development of a thermoacoustic oxidant sensor (TAOS) array to quantify gases that play critical roles in the chemical evolution of the martian surface and atmosphere. The sensor combines a chemiresistor with an acoustic wave-plate device, micro-fabricated on thermally isolated hot-plates; their measurement modes are respectively: conductivity changes of chemically sensitive films, and mass changes of the same coatings. Metal Phthalocyanines (MePcs) and other organic semiconductors such as 1,4-polybutadiene are used as chemical coatings because of their chemical stability and the fact that these compounds have been shown to exhibit selectivity to oxidizing gases. The specific target gases of this experiment are H2O2, H2O, O3 and CO. Identification and quantification of these gases at the martian surface would contribute to both atmospheric and soil chemistry studies. The species H2O2 and/or O3, may be responsible for the unique reactive properties of the martian regolith, as discovered in the Viking biology experiments. In addition, each of the target gases are believed to play a role in the photochemical recycling of CO2.