Monitoring of Dust Devil Tracks Around the InSight Landing Site, Mars, and Comparison With In Situ Atmospheric Data

Abstract

The NASA InSight mission on Mars is a unique opportunity to study atmospheric processes both from orbit and in situ observations. We use post-landing high-resolution satellite images to monitor dust devil activity during the first 8 months of the mission. We perform mapping and semiautomatic detection of newly formed dust devil tracks and analyze their characteristics (sizes, azimuths, distances, and directions of motion). We find a large number of tracks appearing shortly after landing, followed by a significant decrease of activity during late winter, then a progressive increase during early spring. New tracks are characterized by dark linear, to slightly curvilinear, traces ranging from a few to more than 10 m wide. Tracks are oriented in the ambient wind direction, according to measurements made by InSight's meteorological sensors. The systematic analysis of dust devil tracks is useful to have a better understanding of atmospheric and aeolian activity around InSight. Plain Language SummaryThe NASA InSight mission landed on Mars in November 2018. It carries weather and seismic stations that are now working continuously. We are also able to observe the InSight region from orbit using high-resolution satellite images that have been acquired regularly over the first year of the InSight mission. They show a lot of dark traces on the surface, which are caused by whirlwinds called dust devils raising dust into the air. This phenomenon is not observed at the same rate over the entire year, as it depends on atmospheric conditions that vary with season. Our study with satellite images allows us to understand the characteristics of dust devil tracks and compare them with related measurements from the weather station on board InSight. These two sets of observations are well correlated to each other and provide significant constraints to better characterize the atmospheric activity around InSight and in the region of Elysium Planitia, Mars.

A Study of Daytime Convective Vortices and Turbulence in the Martian Planetary Boundary Layer Based on Half‐a‐Year of InSight Atmospheric Measurements and Large‐Eddy Simulations

“…This is clearly much larger than the minimum formation rate of 0.04–0.06 tracks per sol per km 2 found by Perrin et al. (2020), even considering the very exceptional period of intense dust devil activity at the beginning of the InSight mission (i.e., 0.68 tracks/sol/km 2 ). Actually, this “threshold” value of 1 ms −1 is chosen to be permissive to detect enough tracks to form a reasonable statistics to compare to images in Perrin et al.…”

“…Although no visible dust devils have been detected by the InSight cameras (Banfield et al., 2020), numerous fresh tracks were detected from orbit in the region of the InSight landing site (Perrin et al., 2020), sometimes corresponding to tracks identified by InSight cameras (Banerdt et al. (2020) and Charalambous et al., in revision for this issue).…”

“…Actually, this “threshold” value of 1 ms −1 is chosen to be permissive to detect enough tracks to form a reasonable statistics to compare to images in Perrin et al. (2020) in the next paragraph. A normal track formation rate, like in Perrin et al.…”

“…The "contrast" of the image is set by defining the same color for all friction velocities below 1 ms −1 , this color acting as a proxy for undisturbed Martian soil devoid of dark tracks. The "equivalent orbital image" of dark tracks obtained from LES is then analyzed with the exact same semi-automated tracking procedure explained in Perrin et al (2020). Figure 13) rather than InSight-equivalent time series.…”

“…The topics related to PBL dynamics left out of the current study are detailed in the other papers of this issue: notable individual dust devil events (Lorenz et al, 2020), seismic signatures of vortices (Murdoch et al, in revision, Kenda et al, 2020), orbital observations of vortex tracks (Perrin et al, 2020), and aeolian science with InSight (Baker et al, 2020; in revision for this issue). As is shown in Banfield et al (2020), InSight has a great potential too for studies of the nighttime, shear-driven turbulence associated with the nocturnal inversion.…”