Martian dust storm distribution and annual cycle from Mars daily global map observations

Abstract

Dust storms were manually tracked in Mars Reconnaissance Orbiter (MRO) Mars Daily Global Maps (MDGMs) from Mars Year 29 to 33. The data were used to construct the Mars Dust Storm Sequence Dataset (MDSSD), which contains >12,000 dust storm instances that are distinguishable from the ubiquitous dust background. Based on the dust storm climatology, we propose a partition of a Mars year into six pseudo-seasons or “sextons” (named “Unober”, “Duober”, “Triober”, “Quartober”, “Quintober”, and “Sixtober”, respectively). The greatest dust storm activity is observed in the 3rd, 4th and 6th sextons (Triober, Quartober and Sixtober), with each containing one or more dust storm episodes. We also propose a hierarchical system for organizing information and describing the process through which dust storms develop. The hierarchy of storm behavior is described in terms of dust storm episodes within these sextons, with each episode being composed of one or more dust storm sequences, and with each dust storm sequence being composed of multiple dust storm members.The occurrence of a large dust storm episode typically results from multiple dust storm sequences that are simultaneous, staggered, or merged, though one of the component sequences typically plays a dominant role. The typical evolutionary pathway through which a large dust storm sequence develops consists of dust activity progressing from the northern to the southern hemispheres, with multiple flushing dust storm members in the northern hemisphere and followed by a much larger zonally extended dust storm member in the southern hemisphere. Differences among Mars years are related to the timing, order, and trajectories of dust storm sequences, though the overall spatial coverage of dust storm instances within a sexton is similar across years. A striking characteristic of Martian dust storm distribution is the quasi-periodic recurrence exhibited by dust storm episodes and dust storm sequences.