Convective Vortices and Dust Devils Detected and Characterized by Mars 2020

Abstract

We characterize vortex and dust devils (DDs) at Jezero from pressure and winds obtained with the Mars Environmental Dynamics Analyzer (MEDA) instrument on Mars 2020 over 415 Martian days (sols) (Ls = 6°–213°). Vortices are abundant (4.9 per sol with pressure drops >0.5 Pa correcting from gaps in coverage) and they peak at noon. At least one in every five vortices carries dust, and 75% of all vortices with Δp > 2.0 Pa are dusty. Seasonal variability was small but DDs were abundant during a dust storm (Ls = 152°–156°). Vortices are more frequent and intense over terrains with lower thermal inertia favoring high daytime surface-to-air temperature gradients. We fit measurements of winds and pressure during DD encounters to models of vortices. We obtain vortex diameters that range from 5 to 135 m with a mean of 20 m, and from the frequency of close encounters we estimate a DD activity of 2.0–3.0 DDs km−2 sol−1. A comparison of MEDA observations with a Large Eddy Simulation of Jezero at Ls = 45° produces a similar result. Three 100-m size DDs passed within 30 m of the rover from what we estimate that the activity of DDs with diameters >100 m is 0.1 DDs km−2sol−1, implying that dust lifting is dominated by the largest vortices in Jezero. At least one vortex had a central pressure drop of 9.0 Pa and internal winds of 25 ms−1. The MEDA wind sensors were partially damaged during two DD encounters whose characteristics we elaborate in detail.