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Originally published in Science Express on 7 October 2004
Science 19 November 2004:
Vol. 306. no. 5700, pp. 1364 - 1367
DOI: 10.1126/science.1098496
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Reports

Mars' South Polar Ar Enhancement: A Tracer for South Polar Seasonal Meridional Mixing

A. L. Sprague,1* W. V. Boynton,1 K. E. Kerry,1 D. M. Janes,1 D. M. Hunten,1 K. J. Kim,2 R. C. Reedy,2 A. E. Metzger3

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.

1 Lunar and Planetary Laboratory, 1629 East University Boulevard, University of Arizona, Tucson, AZ 85721–0092, USA.
2 Institute of Meteoritics, MSC03-2050, University of New Mexico, Albuquerque, NM 87131–0001, USA.
3 Jet Propulsion Laboratory, Pasadena, CA 91109, USA.

* To whom correspondence should be addressed. E-mail: sprague{at}lpl.arizona.edu

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