THEMIS Observations of the 2018 Mars Global Dust Storm

We present Thermal Imaging System (THEMIS) infrared observations taken during the recent global dust storm that occurred during the summer of 2018 (Mars Year 34). THEMIS observations of the dust storm show the distinct thermal signature of the storm and the spatial and temporal variation of column dust optical depth before, during, and after the storm. Dust optical depth was observed by THEMIS to increase in two stages, initially at L-s = 185 degrees and then again after L-s = 195 degrees. Peak globally average dust optical depth was attained at L-s = 205 degrees, which was followed by a relatively rapid decrease in dust loading. Evening atmospheric temperatures warmed by more than 20 K at all observed latitudes and by as much as 40 K at high southern latitudes. Morning atmospheric temperatures were also observed to warm but by a smaller amount (similar to 15 K) and with a different latitude dependence. A comparison to global dust storms that occurred in Mars Years 25 and 28 shows similarities in the thermal response but differences in the details of the time history of dust optical depth. Each global dust storm is unique, and the new observations of this most recent storm will provide important new clues to the physical processes that govern these storms.