Argon in the Martian atmosphere

Heretofore undetected argon may be a significant constituent of the Martian atmosphere with a partial pressure of 1.8 mbar. The addition of argon to the 5.5 plus or minus 0.8 mbar of CO2, deduced from ground-based spectroscopy, is consistent with the values of total pressure deduced from the Mariner radio occulation measurements. The presence of argon in the Martian atmosphere contributes to the cooling of the upper thermosphere and exosphere and may explain the difference between predicted and observed temperatures. The argon concentrations predicted here may be related to the recent observation of several tens of per cent of an inert gas, deduced from Mars-6 data.