Seasonal Atmospheric Argon Variability Measured in the Equatorial Region of Mars by the Mars Exploration Rover Alpha Particle X-Ray Spectrometers: Evidence for an Annual Argon-Enriched Front

作者：VanBommel S J^*; Gellert R; Clark B C; Ming D W

来源：JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE, 2018, 123(2): 544-558.

DOI：10.1002/2017JE005454

• Mars
• atmosphere
• argon
• APXS
• circulation
• noncondensable

The Mars Exploration Rover Opportunity (MER-B) has been exploring the surface of Mars since landing in 2004. Its Alpha Particle X-ray Spectrometer (APXS) is primarily used to interrogate the chemical composition of rocks and soil samples in situ. Additionally, the APXS has measured the atmosphere of Mars with a regular cadence, monitoring the change in relative atmospheric argon density. Atmospheric measurements with the MER-B APXS span over six Mars years providing an unprecedented level of statistics for careful study of the ubiquitous APXS spectral background. Several models were applied to high-frequency long-duration Spirit rover atmospheric APXS measurements. The most stable model with the least uncertainty was applied to the MER-B data set. Seasonal variation of 10-15% in equatorial atmospheric argon density was observed - in agreement with existing literature and global climate models. Unseen in previous work and global climate models, an abrupt deviation from the model-predicted annual mixing ratio was measured by the MER-B APXS around L-s 150. The sharp change, similar to 10% over 10 degrees L-s, provides strong evidence for a northward migrating front, enriched in argon, sourced from the south pole at the end of southern winter. A similar weaker front is possibly observed around L-s 325, sourced from the northern polar region.

• 出版日期2018-2