Similarities and Differences of Global Dust Storms in MY 25, 28, and 34

To better understand the dust cycle on Mars during years with planet‐encircling dust storms,
we analyze the last three events that took place in Mars Year (MY) 25, MY 28, and MY 34. Global dust storms that occurred in MY 25 and MY 34 (June 2018) were taking place during equinox, while the MY 28 storm had an onset after perihelion. Before the expansion phase of the MY 25 and MY 34 storms, we find similar regions (northern rim of Hellas, Arabia Terra, and Utopia Planitia) where dust is present. Possible precursor dust storms over Hellas and the southern polar cap edges were observed during MY 28 as a component of background dust activity. These features are not found in equinoctial dust storms on this scale. Dust during the MY 25 and MY 34 storms encircled the entire planet by the similar season (L(s) = 193°). The MY 34 storm is characterized by a shorter decay phase compared to the events in MY 25 and MY 28. Dust opacity is correlated with atmospheric temperatures at 0.5 mbar and nighttime surface temperatures, while daytime surface temperatures are anticorrelated with dust opacity.