Mars' south polar Ar enhancement: A tracer for south polar seasonal meridional mixing

The gamma ray spectrometer on the Mars Odyssey spacecraft measured an enhancement of atmospheric argon over southern high latitudes during autumn followed by dissipation during winter and spring. Argon does not freeze at temperatures normal for southern winter (∼145 kelvin) and is left in the atmosphere, enriched relative to carbon dioxide (CO₂), as the southern seasonal cap of CO₂ frost accumulates. Calculations of seasonal transport of argon into and out of southern high latitudes point to meridional (north-south) mixing throughout southern winter and spring.