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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, E03S13, doi:10.1029/2006JE002832, 2007

Long-term observations of southern winters on Mars: Estimations of column thickness, mass, and volume density of the seasonal CO2 deposit from HEND/Odyssey data

M. L. Litvak

Space Research Institute, Moscow, Russia


I. G. Mitrofanov

Space Research Institute, Moscow, Russia


A. S. Kozyrev

Space Research Institute, Moscow, Russia


A. B. Sanin

Space Research Institute, Moscow, Russia


V. I. Tretyakov

Space Research Institute, Moscow, Russia


W. V. Boynton

Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA


N. J. Kelly

Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA


D. Hamara

Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA


R. S. Saunders

NASA Headquarters, Washington, D. C., USA


Abstract

In this paper, we have analyzed neutron spectroscopy data gathered by the High Energy Neutron Detector (HEND) instrument on board Mars Odyssey for two Martian years of orbital mapping. We focused on the observations of the Martian southern seasonal cap for this period of time. Nuclear methods based on numerical modeling allow us to derive an estimation of the distribution of CO2 frost column density and mass from the temporal variations of neutron flux between summer and winter seasons. We have estimated the seasonal behavior of both the column density and mass of CO2 frost. Comparison between two Martian years revealed minor (<10%) interannual variations of CO2 thickness at the south pole during the middle of southern winter. It was found that maximal mass of the southern seasonal cap is achieved at Ls = 160° and is equal to 6.6 ± 0.6 × 1015 kg. We found that this result corresponds well with previous HEND results, NASA Ames GCM predictions, Gamma Ray Spectrometer estimates, and estimations from gravity models based on MGS and Mars Odyssey tracking data. In our analysis, we also compared to processed MOLA data (linear thicknesses of snow depths) to measure the value of the volume density of the Southern seasonal cap, and we found that it may vary in the range 400–1250 kg/m3.

Received 21 September 2006; accepted 5 January 2007; published 17 February 2007.

Keywords: Mars CO2; seasonal polar caps; carbon dioxide cycle.

Index Terms: 5462 Planetary Sciences: Solid Surface Planets: Polar regions; 5422 Planetary Sciences: Solid Surface Planets: Ices; 5464 Planetary Sciences: Solid Surface Planets: Remote sensing; 6225 Planetary Sciences: Solar System Objects: Mars.

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Citation: Litvak, M. L., I. G. Mitrofanov, A. S. Kozyrev, A. B. Sanin, V. I. Tretyakov, W. V. Boynton, N. J. Kelly, D. Hamara, and R. S. Saunders (2007), Long-term observations of southern winters on Mars: Estimations of column thickness, mass, and volume density of the seasonal CO2 deposit from HEND/Odyssey data, J. Geophys. Res., 112, E03S13, doi:10.1029/2006JE002832.