Surface dust redistribution on Mars as observed by the Mars Global Surveyor and Viking orbiters

Abstract

The variation of surface dust coverage on Mars is mapped using Mars Global Surveyor (MGS) and Viking albedo data. Albedo is shown to correlate well with spectrally derived measurements of surface dust abundance and is subsequently used to gauge dust coverage. Atmospheric aerosols modify the albedo observed from orbit, complicating this analysis. However, opacity cycles are highly repeatable, and simultaneous, independent records of aerosol opacities are available to isolate their impact. The MGS albedo and imaging data contain global coverage on a daily basis, allowing the relationship between dust cover and specific meteorological events to be elucidated. The 2001 global dust storm produced the largest changes in surface dust coverage during the MGS mission. Other processes yielding significant changes include seasonal cap‐edge winds, seasonally varying regional winds, local/regional dust storms, and extratropical cyclones. Dust devils and ongoing, small‐scale dust lifting do not appear to significantly modify the global patterns of dust cover. Finally, we show that the apparent long‐term darkening of the southern mid and high latitudes between the Viking and MGS eras is largely a consequence of the timing of image acquisition relative to global dust storms and surface dust “cleaning” by the seasonal ice cap; it does not represent a steady decadal‐scale, secular change. In fact, following the 2001 global dust storm, in late southern spring, the southern hemisphere was brighter in MGS than in Viking data. This study reveals albedo to be a dynamic, climatological variable for Mars, similar to sea‐surface temperature for terrestrial meteorology and climate.