Atmospheric dust is a more extreme modifier of weather and climate on Mars than water vapor is on Earth. Global dust storms enshroud Mars in a veil of dust for months and have major implications for past and present climate, geologic history, habitability, and exploration. Yet their mysterious origins mean we remain unable to realistically simulate or predict them. In this White Paper, we find that key Knowledge Gaps are: A. how dust is lifted; B. constraints on near-surface winds and boundary-layer processes; C. the distribution of mobile surface dust; and D. the key processes and feedbacks by which dust storms begin and evolve. To make progress in the next decade, we make four Recommendations in order of priority: #1. Properly accommodate a minimum payload of meteorological and aeolian sensors on future Mars surface missions; #2. Continue orbital monitoring of the evolving surface dust distribution; #3. Expand orbital measurements to include winds and full diurnal coverage; and #4. Continue orbital monitoring and add surface measurements of aerosols during dust storms.

BACKGROUND Dust devils are small-scale (few to many tens of meters) low-pressure vortices rendered visible by lofted dust. They usually occur in arid climates on the Earth and ubiquitously on Mars. Martian dust devils have been studied with orbiting and landed spacecraft and were first identified on Mars using images from the Viking Orbiter . On Mars, dust devils may dominate the supply of atmospheric dust and influence climate , pose a hazard for human exploration , and they may have lengthened the operational lifetime of Martian rovers . On the Earth, dust devils significantly degrade air quality in arid climates and may pose an aviation hazard . The dust-lifting capacity of dust devils seems to depend sensitively on their structures, in particular on the pressure wells at their centers , so the dust supply from dust devils on both planets may be dominated by the seldom-observed larger devils. Using a martian global climate model, showed that observed seasonal variations in Mars’ near-surface temperatures could not be reproduced without including the radiative effects of dust and estimated the dust contributes more than 10 K of heating to the heating budget. Thus, elucidating the origin, evolution, and population statistics of dust devils is critical for understanding important terrestrial and Martian atmospheric properties and for in-situ exploration of Mars. Studies of Martian dust devils have been conducted through direct imaging of the devils and identification of their tracks on Mars’ dusty surface \citep[cf.][]{Balme_2006}. Studies with in-situ meteorological instrumentation have also identified dust devils, either via obscuration of the Sun by the dust column or their pressure signals . Studies have also been conducted of terrestrial dust devils and frequently involve in-person monitoring of field sites. Terrestrial dust devils are visually surveyed , directly sampled , or recorded using in-situ meteorological equipment . As noted in , in-person visual surveys are likely to be biased toward detection of larger, more easily seen devils. Such surveys would also fail to recover dustless vortices . Recently, terrestrial surveys similar to Martian dust devil surveys have been conducted using in-situ single barometers and photovoltaic sensors . These sensor-based terrestrial surveys have the advantage of being directly analogous to Martian surveys and are highly cost-effective compared to the in-person surveys (in a dollars per data point sense). In single-barometer surveys, a sensor is deployed in-situ and records a pressure time series at a sampling period ≲1 s. Since it is a low-pressure convective vortex, a dust devil passing nearby will register as pressure dip discernible against a background ambient (but not necessarily constant) pressure. Figure [fig:conditioning_detection_b_inset] from shows a time-series with a typical dust devil signal.