Variability of Mars' North Polar water ice cap: I. Analysis of Mariner 9 and Viking Orbiter imaging data

By: , and 



Previous studies interpreted differences in ice coverage between Mariner 9 and Viking Orbiter observations of Mars' north residual polar cap as evidence of interannual variability of ice deposition on the cap. However, these investigators did not consider the possibility that there could be significant changes in the ice coverage within the northern residual cap over the course of the summer season. Our more comprehensive analysis of Mariner 9 and Viking Orbiter imaging data shows that the appearance of the residual cap does not show large-scale variance on an interannual basis. Rather we find evidence that regions that were dark at the beginning of summer look bright by the end of summer and that this seasonal variation of the cap repeats from year to year. Our results suggest that this brightening was due to the deposition of newly formed water ice on the surface. We find that newly formed ice deposits in the summer season have the same red-to-violet band image ratios as permanently bright deposits within the residual cap. We believe the newly formed ice accumulates in a continuous layer. To constrain the minimum amount of deposited ice, we used observed albedo data in conjunction with calculations using Mie theory for single scattering and a delta-Eddington approximation of radiative transfer for multiple scattering. The brightening could have been produced by a minimum of (1) a ~35-μm-thick layer of 50-μm-sized ice particles with 10% dust or (2) a ~14-μm-thick layer of 10-μm-sized ice particles with 50% dust.

Publication type Article
Publication Subtype Journal Article
Title Variability of Mars' North Polar water ice cap: I. Analysis of Mariner 9 and Viking Orbiter imaging data
Series title Icarus
DOI 10.1006/icar.1999.6300
Volume 144
Issue 2
Year Published 2000
Language English
Publisher Elsevier
Contributing office(s) Astrogeology Science Center
Description 15 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Icarus
First page 382
Last page 396
Other Geospatial Mars
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