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The Curiosity Rover has been exploring the Gale Crater using the on‐board Navigation Camera to monitor the line‐of‐sight (LOS) dust extinction within the crater. Previous studies of the line‐of‐sight extinction have shown an annual trend where a minimum in extinction occurs around Ls = 100° and a maximum occurs around Ls = 300°. However, past studies have been constrained to images acquired only between 10:00 and 14:00 local time, limiting our understanding of the variation of dust extinction in Gale Crater throughout the day. Here, using a method that corrects for variable lighting geometry, we reanalyze the line‐of‐sight images captured throughout the mission to include images acquired in the early morning and late afternoon. Additionally, we update the line‐of‐sight record to include over 1,000 additional sols of the mission through sol 3,663, which updates our record of extinction in Gale to the end of Mars Year 36—a period of almost 5.5 Mars Years. Using images taken throughout the sol, we examine the diurnal trend in dust extinction, where a maximum is seen around solar noon. This diurnal trend is observed throughout the year, with a larger diurnal variation observed during the southern summer. Additionally, the geographic homogeneity in dust loading is quantified, with higher dust loading observed in the western portion of the line‐of‐sight images, corresponding with the north‐western portion of the crater rim. These observations suggest that dust lifting from the surface and vertical mixing are factors in the diurnal, seasonal, and geographic dynamics observed in the extinctions. Plain Language Summary: The Curiosity Rover has used its Navigation Camera to image the northern rim of Gale Crater for over 3,000 martian days. These images are used to calculate the amount of airborne dust between the rover and the crater rim. Past studies using these images found that the amount of dust was lowest during southern‐hemisphere winter and highest during southern‐hemisphere summer. In this work, a new method to find the amount of dust was used, allowing us to use images taken throughout the day for the first time. The entire set of crater rim images was reanlayzed using the new method, including new images captured up to sol 3,663. We find a daily cycle, where the amount of dust in the air is lowest in the morning and evening, and highest around noon. In addition, there is more airborne dust between the rover and the crater rim on the western side of the image compared with the center and eastern side. This suggests that dust is moving within the Gale Crater on short timescales, where dust lifting from the surface likely plays a key role in the diurnal trend, in combination with air outside the crater mixing with air within the crater. Key Points: The line‐of‐sight dust extinction is calculated through 3,663 sols using the Mars Science Laboratory's Navigation CameraDiurnally, the dust extinction peaks at solar noon, with lower values in the morning and eveningThe diurnal variation is higher during the dustier southern summer and lower during the southern winter when dust extinction is at a minimum [ABSTRACT FROM AUTHOR]

Measurements of ground and near surface atmospheric temperatures at Jezero obtained during 700 sols by the Mars Environmental Dynamics Analyzer (MEDA) characterize the thermal behavior of the near surface Martian atmosphere during a full Martian Year. The seasonal evolution of MEDA measurements is compared with predictions from the Mars Climate Database and the solar irradiance at the surface. Thermal tides observed in the daily cycle of temperatures follow a seasonal cycle with additional variations greater than 2 K on time‐scales of tens of sols. We also observe sol‐to‐sol variations of about 1 K in mean daily air temperatures in autumn and winter with periodicities of 4–7 sols that might be related to baroclinic disturbances that are frequent in those seasons at high latitudes. We examine the evolution of the vertical thermal gradient and temperature fluctuations without finding a seasonal response to irradiance and dust load. We find that the convective boundary layer becomes isothermal and collapses 1 hr before sunset except during northern hemisphere winter, when the collapse occurs closer to sunset, implying a longer duration of the daytime convective instability. Around this period, the rover was located in the delta front in a location of complex topography where we observed stronger thermal gradients and intense daytime air temperature fluctuations. We also find in this place a nighttime event of gravity waves on near‐surface air temperatures, with amplitudes of 2 K and periods of 10 min. These waves possibly propagate downward through a near isothermal stable layer. Plain Language Summary: The Perseverance rover on Mars is carrying a meteorological station that among other measurements obtains air temperatures at three heights near the surface as well as ground temperatures. We analyze seasonal and local changes in temperatures measured over one Martian year (687 Earth days) in which Perseverance moved several kilometers across Jezero crater, comparing in situ observations with the output from a Global Climate Model of the atmosphere of Mars. Our results show that the diurnal cycle of temperatures is modulated by the solar irradiance on the surface, the amount of dust in the atmosphere, local dynamics and large‐scale weather systems. The temperature difference between the ground and the atmosphere greatly determines the meteorology in the lower atmosphere. Neither this temperature difference, nor temperature fluctuations, which during daytime are a proxy of atmospheric convection driven by the heating of the surface, show seasonal variations in line with the seasonal solar irradiance or dust load. Instead, the rover path toward a more complex topography led to the highest surface‐to‐air temperature difference during the northern hemisphere winter, despite the solar irradiance being minimum at that time. Close to this complex topography, the meteorological station recorded oscillations in near‐surface temperature related to gravity waves. Key Points: Seasonal variations in irradiance at Mars' surface drive observed daily mean near‐surface air temperatures with some differences from modelsThermal tides and long‐period traveling waves present a clear seasonal cycle with autumn and winter seasons more prone to variabilityAir temperatures underwent non‐seasonal changes near Jezero's delta, with strong daytime convection and nighttime gravity waves [ABSTRACT FROM AUTHOR]

We quantify the effect of dust accumulation at Jezero crater by means of a Dust Correction Factor (DCF) for the solar radiation measured by the photodiodes of the Radiation and Dust Sensor of the Mars 2020 mission. After one Mars Year, dust on the photodiode surface attenuated 25%–30% of the incoming solar radiation. The DCF did not decrease monotonically; we use a model to reproduce its evolution and to derive dust deposition and lifting rates, showing that dust removal is 9 times larger at Jezero crater than at InSight's location in western Elysium Planitia. The model fit obtained using observed opacities is further improved when fed with dust sedimentation rates simulated by a GCM that considers a particle size distrtibution. Projections show seasonal net dust removal, being encouraging for the long‐term survival of solar‐powered missions to Jezero or similarly active dust lifting regions. Plain Language Summary: Dust is ubiquitous in the Martian atmosphere, accumulating on both natural and artificial surfaces. Dust particularly affects the performance and lifetime of missions: the termination of InSight and MER‐B operations are recent examples. Dust accumulation shows a seasonal behavior, and attenuated 25%–30% of the incoming solar radiation on Perseverance after the first Mars Year of the mission. Dust removal is almost 10 times larger than at InSight's location: projections indicate that surfaces at Jezero will be periodically partially cleaned. The estimations of the effect of the accumulated dust as a function of time are encouraging for solar‐powered missions to regions with similar amounts of dust lifting, which might be determined from orbital data on where dust storms originate, dust devils or their tracks are found, or seasonal albedo changes are noted. In addition, the quantification of the effect of accumulated enables future studies requiring more accurate knowledge of incoming solar radiation at the surface. Key Points: We present the evolution of dust accumulation at Jezero crater for more than one Mars YearWe derive dust deposition and removal rates: removal is 9 times more efficient than at the InSight location in western Elysium PlanitiaProjections show that surfaces at Jezero will experience seasonal net dust removal, encouraging solar‐powered missions [ABSTRACT FROM AUTHOR]

Mars 2020 Mars Environmental Dynamics Analyzer (MEDA) instrument data acquired during half of a Martian year (Ls 13°–180°), and modeling efforts with the Mars Regional Atmospheric Modeling System (MRAMS) and the Mars Climate Database (MCD) enable the study of the seasonal evolution and variability of nocturnal atmospheric turbulence at Jezero crater. Nighttime conditions in Mars's Planetary Boundary Layer are highly stable because of strong radiative cooling that efficiently inhibits convection. However, MEDA nighttime observations of simultaneous rapid fluctuations in horizontal wind speed and air temperatures suggest the development of nighttime turbulence in Jezero crater. Mesoscale modeling with MRAMS also shows a similar pattern and enables us to investigate the origins of this turbulence and the mechanisms at play. As opposed to Gale crater, less evidence of turbulence from breaking mountain wave activity was found in Jezero during the period studied with MRAMS. On the contrary, the model suggests that nighttime turbulence at Jezero crater is explained by increasingly strong wind shear produced by the development of an atmospheric bore‐like disturbance at the nocturnal inversion interface. These atmospheric bores are produced by downslope winds from the west rim undercutting a strong low‐level jet aloft from ∼19:00 to 01:00 LTST and from ∼01:00 LTST to dawn when undercutting weak winds aloft. The enhanced wind shear leads to a reduction in the Richardson number and an onset of mechanical turbulence. Once the critical Richardson Number is reached (Ri ∼ <0.25), shear instabilities can mix warmer air aloft down to the surface. Plain Language Summary: Mars is highly susceptible to atmospheric turbulence, which refers to the chaotic and instantaneous variation in the thermodynamic magnitudes of the atmosphere. While the Martian nighttime conditions near the surface are typically stable due to strong radiative cooling that efficiently inhibits convection, turbulence can still occur due to wind shear. Wind shear is defined as a change in wind speed and/or direction over a relatively short distance in the atmosphere. This phenomenon can mechanically force turbulence as described in this study using both Mars 2020 rover observations at Jezero crater and numerical modeling efforts. Both observations and modeling show turbulence during the first part of the night and around midnight during most of the times of the year with a clear hiatus in turbulence centered prior to summer solstice. We provide evidence that points toward the wind shear turbulence being caused by atmospheric bore waves inside the crater. Key Points: Nocturnal turbulence at Jezero crater peaks at Ls ∼ 37, Ls ∼ 56, and Ls ∼ 123 with a clear hiatus lasting tens of sols centered at Ls ∼ 83Both observations and modeling show turbulence during the first part of the night and around midnightTurbulence is produced by wind shear originating from the passage of an atmospheric bore wave related to downslope winds from the west rim [ABSTRACT FROM AUTHOR]

The Mars Environmental Dynamics Analyzer instrument, on board NASA's Mars 2020 Perseverance rover, includes a number of sensors to characterize the Martian atmosphere. One of these sensors is the Radiation and Dust Sensor (RDS) that measures the solar irradiance at different wavelengths and geometries. We analyzed the RDS observations made during twilight for the period between sol 71 and 492 of the mission (Ls 39°–262°, Mars Year 36) to characterize the clouds over the Perseverance rover site. Using the ratio between the irradiance at zenith at 450 and 750 nm, we inferred that the main constituent of the detected high‐altitude aerosol layers was ice from Ls = 39°–150° (cloudy period), and dust from Ls 150°–262°. A total of 161 twilights were analyzed in the cloudy period using a radiative transfer code and we found: (a) signatures of clouds/hazes in the signals in 58% of the twilights; (b) most of the clouds had altitudes between 40 and 50 km, suggesting water ice composition, and had particle sizes between 0.6 and 2 µm; (c) the cloud activity at sunrise is slightly higher that at sunset, likely due to the differences in temperature; (d) the time period with more cloud detections and with the greatest cloud opacities is during Ls 120°–150°; and (e) a notable decrease in the cloud activity around aphelion, along with lower cloud altitudes and opacities. This decrease in cloud activity indicates lower concentrations of water vapor or cloud condensation nuclei (dust) around this period in the Martian mesosphere. Plain Language Summary: During twilight, ground‐based observations of the irradiance allows the detection and characterization of high‐altitude clouds (above 30–35 km). Because the sun is at or below the horizon, the cloud layers reflect the direct light that only reaches the higher parts of the atmosphere, producing an increase in the sky brightness with respect to the cloud‐free scenario. Moreover, the decrease in the intensity with the solar zenith angle highly depends on the cloud altitude and density. Using observations made by the Radiation and Dust Sensor, part of the instrument Mars Environmental Dynamics Analyzer on board Perseverance rover, we present here a study of the twilight clouds detected at the Perseverance landing site for the first 490 sols of the mission (Mars Year 36). By modeling the irradiance at 450 and 950 nm with radiative transfer simulations, we constrained the cloud altitude, opacity, and particle radius. The number of twilights analyzed allowed us to study the seasonal trend in the cloud activity. During the cloudy period, Ls 39°–150°, we find a significant decrease in the cloud activity above 30–35 km around aphelion (Ls ∼ 70°). This implies that the seasonal distribution of clouds above 30–35 km differs from that observed at lower altitudes. Key Points: Most of the cloud detected at twilight between sol 71 and 492 of the Mars 2020 mission (Ls 39°–262°) occurred at altitudes between 40 and 50 kmAround aphelion (Ls ∼ 70°) we found the minimum in cloud activity and lower cloud opacitiesThe cloud activity at sunrise is slightly stronger than at sunset and this is likely due to the lower temperatures [ABSTRACT FROM AUTHOR]

We identify temporal variations in surface albedo at Jezero crater using first‐of‐their‐kind high‐cadence in‐situ measurements of reflected shortwave radiation during the first 350 sols of the Mars 2020 mission. Simultaneous Mars Environmental Dynamics Analyzer (MEDA) measurements of pressure, radiative fluxes, winds, and sky brightness indicate that these albedo changes are caused by dust devils under typical conditions and by a dust storm at Ls ∼ 155°. The 17% decrease in albedo caused by the dust storm is one order of magnitude larger than the most apparent changes caused during quiescent periods by dust devils. Spectral reflectance measurements from Mastcam‐Z images before and after the storm indicate that the decrease in albedo is mainly caused by dust removal. The occurrence of albedo changes is affected by the intensity and proximity of the convective vortex, and the availability and mobility of small particles at the surface. The probability of observing an albedo change increases with the magnitude of the pressure drop (ΔP): changes were detected in 3.5%, 43%, and 100% of the dust devils with ΔP < 2.5 Pa, ΔP > 2.5 Pa and ΔP > 4.5 Pa, respectively. Albedo changes were associated with peak wind speeds above 15 m·s−1. We discuss dust removal estimates, the observed surface temperature changes coincident with albedo changes, and implications for solar‐powered missions. These results show synergies between multiple instruments (MEDA, Mastcam‐Z, Navcam, and the Supercam microphone) that improve our understanding of aeolian processes on Mars. Plain Language Summary: Small particles at the surface of Mars are lifted and transported through interactions with the atmosphere, modifying the fraction of solar radiation reflected by the surface (albedo). We analyzed the first albedo measurements acquired at 1 Hz and other environmental variables measured at Jezero crater, concluding that albedo changes are caused by dust devils under typical conditions and by a dust storm. The darkening of the surface induced by the storm is around 10 times larger than that caused in the absence of a storm by dust devils. Surface images indicate that this darkening is caused by dust removal. Only a fraction of the dust devils cause an albedo change, depending on their intensity, size and trajectory, and on the features of the small particles at the surface. The combined analysis of environmental variables, images and microphone recordings acquired by the Mars 2020 mission improve our understanding of the processes involved in the lifting and transport of small particles. Key Points: We identify surface albedo changes using Mars 2020 first‐of‐their‐kind high‐cadence in situ measurements of reflected solar radiationThe most remarkable albedo changes observed within seconds outside dust storm conditions were caused by dust devilsA multi‐instrument analysis showed that the dust storm reduced surface albedo by more than 15%, primarily caused by dust removal [ABSTRACT FROM AUTHOR]

The Mars Environmental Dynamics Analyzer instrument on Mars 2020 has five Atmospheric Temperature Sensors at two altitudes (0.84 and 1.45 m) plus a Thermal InfraRed Sensor that measures temperatures on the surface and at ∼40 m. We analyze the measurements from these sensors to describe the evolution of temperatures in Jezero up to mission sol 400 (solar longitude LS = 13°–203°). The diurnal thermal cycle is characterized by a daytime convective period and a nocturnal stable atmosphere with a variable thermal inversion. We find a linear relationship between the daytime temperature fluctuations and the vertical thermal gradient with temperature fluctuations that peak at noon with typical values of 2.5 K at 1.45 m. In the late afternoon (∼17:00 Local True Solar Time), the atmosphere becomes vertically isothermal with vanishing fluctuations. We observe very small seasonal changes in air temperatures during the period analyzed. This is related to small changes in solar irradiation and dust opacity. However, we find significant changes in surface temperatures that are related to the variety of thermal inertias of the terrains explored along the traverse of Perseverance. These changes strongly influence the vertical thermal gradient, breaking the nighttime thermal inversion over terrains of high thermal inertia. We explore possible detections of atmospheric tides on near‐surface temperatures and we examine variations in temperatures over timescales of a few sols that could be indicative of atmospheric waves affecting near‐surface temperatures. We also discuss temperatures during a regional dust storm at LS = 153°–156° that simultaneously warmed the near surface atmosphere while cooling the surface. Plain Language Summary: The Mars Environmental Dynamics Analyzer instrument on the Mars 2020 Perseverance rover records temperatures in Jezero at four altitudes from the surface to 40 m. We describe the evolution of temperatures over the first 400 Martian days of the mission from northern spring to early autumn. Diurnal temperatures show an unstable convective regime during the daytime and a stable atmosphere at night. Daytime convection produces thermal fluctuations that peak at noon with typical values of 2.5 K at 1.45 m. These thermal fluctuations vanish in the late afternoon when an isothermal atmosphere is observed from the surface up to 40 m. We also find a linear relationship between the daytime temperature fluctuations and the thermal gradient between the surface and the atmosphere. We find very little seasonal change in air temperatures. However, the thermal inertia of the terrain affects surface temperatures, and the nighttime thermal inversion breaks over terrains with high thermal inertia. We investigate the possible detection in near surface temperatures of thermal tides and atmospheric waves. Finally, we show the thermal response of the surface and the atmosphere during the passage of a regional dust storm with a simultaneous cooling of the surface and warming of the near‐surface atmosphere. Key Points: Surface and atmospheric temperatures at Jezero show small seasonal variations from Spring to early Autumn that agree with modelsThe intensity of daytime convective fluctuations is correlated with vertical thermal gradients, which depend on the surface thermal inertiaA dust storm significantly heated the lower atmosphere while cooling the surface indicating strong radiative effects of low altitude dust [ABSTRACT FROM AUTHOR]

The Mars Environmental Dynamics Analyzer (MEDA) on board Perseverance includes first‐of‐its‐kind sensors measuring the incident and reflected solar flux, the downwelling atmospheric IR flux, and the upwelling IR flux emitted by the surface. We use these measurements for the first 350 sols of the Mars 2020 mission (Ls ∼ 6°–174° in Martian Year 36) to determine the surface radiative budget on Mars and to calculate the broadband albedo (0.3–3 μm) as a function of the illumination and viewing geometry. Together with MEDA measurements of ground temperature, we calculate the thermal inertia for homogeneous terrains without the need for numerical thermal models. We found that (a) the observed downwelling atmospheric IR flux is significantly lower than the model predictions. This is likely caused by the strong diurnal variation in aerosol opacity measured by MEDA, which is not accounted for by numerical models. (b) The albedo presents a marked non‐Lambertian behavior, with lowest values near noon and highest values corresponding to low phase angles (i.e., Sun behind the observer). (c) Thermal inertia values ranged between 180 (sand dune) and 605 (bedrock‐dominated material) SI units. (d) Averages of albedo and thermal inertia (spatial resolution of ∼3–4 m2) along Perseverance's traverse are in very good agreement with collocated retrievals of thermal inertia from Thermal Emission Imaging System (spatial resolution of 100 m per pixel) and of bolometric albedo in the 0.25–2.9 μm range from (spatial resolution of ∼300 km2). The results presented here are important to validate model predictions and provide ground‐truth to orbital measurements. Plain Language Summary: We analyzed first‐of‐its‐kind measurements from the weather station on board NASA's Perseverance rover. These include the incident solar radiation and the amount that is reflected by the surface, as well as the thermal atmospheric forcing (greenhouse effect) and the thermal heat released by the surface. These measurements comprise the radiant energy budget, which is fundamental to understanding Mars' weather through its impact on temperatures. From the solar measurements, we obtained the surface reflectance for a variety of illuminating and viewing geometries. We found that the thermal atmospheric forcing is weaker than expected from models, likely because of the strong diurnal variation in atmospheric aerosols observed by the rover, which is not accounted for by models. We also found that the surface reflectance is not uniform from all directions, but that it decreases when the Sun is highest in the sky (near noon) and increases when the Sun is directly behind the observer (sunset and sunrise), and thus the shadows cast by their roughness elements (e.g., pores and pits) are minimized. Because models neither consider diurnal variations in atmospheric aerosols nor in the surface reflectance, the results presented here are important to validate model predictions for future human exploration. Key Points: Mars Environmental Monitoring Station (MEDA) allows the first in situ determination of the surface radiative budget on Mars, providing key constraints on numerical modelsMEDA allows the direct determination of thermal inertia and albedo, providing ground‐truth to satellite retrievalsAlbedo shows a strong non‐Lambertian behavior, with minimum values at noon and higher values toward sunrise and sunset [ABSTRACT FROM AUTHOR]

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. Plain Language Summary: Dust devils (DDs) are whirlwinds of warm air with winds strong enough to lift dust. They are common in Earth deserts and much more abundant on Mars, where they are one of the elements that bring dust to the atmosphere. The Mars 2020 mission landed in Jezero crater on February 2020 and has observed a plethora of DDs that we investigate with the meteorological sensors on the Mars Environmental Dynamics Analyzer (MEDA) instrument. Results for more than 400 Martian days from spring to autumn indicate a high abundance of events with small seasonal variability. Terrains with lower thermal inertia, warming more efficiently at noon, favor the appearance of DDs. We also found an increased DD activity during a short dust storm that covered the region. From modeling MEDA data, we find that DDs at Jezero have diameters from 5.0 to 135 m. We estimate that about 2–3 DDs are formed per km2 and Martian day. Large vortices with diameters of 100 m form frequently enough to dominate dust lifting at Jezero. Two DDs damaged part of the hardware of the wind sensors of MEDA and we detail the characteristics of those events. Key Points: Vortices and dust devils (DDs) are frequent on Jezero. Mars Environmental Dynamics Analyzer detects 5.0 and 1.0 events per sol respectively when correcting from sampling effectsIntense vortices on Jezero tend to be dusty with 75% of all vortices with a pressure drop larger than 2.0 Pa being dustyWe calculate 2.5 and 0.1 DDs km−2sol−1 with sizes of 20 and 100 m respectively. The largest events dominate dust lifting [ABSTRACT FROM AUTHOR]

The Mars Environmental Dynamics Analyzer, onboard the Perseverance rover, is a meteorological station that is operating on Mars and includes, among other sensors, the radiometer Radiation and Dust Sensor (RDS). From RDS irradiance observations, a total of 374 dust devils (DDs) were detected for the first 365 sols of the mission (Ls = 6°–182°), which along with wind and pressure measurements, we estimated a DD frequency of formation at Jezero between 1.3 and 3.4 DD km−2 sol−1 (increasing as we move from spring into summer). This frequency is found to be smaller than that estimated at the Spirit or Pathfinder landing sites but much greater than that derived at InSight landing site. The maximum in DD frequency occurs between 12:00 and 13:00 local true solar time, which is when the convective heat flux and lower planetary boundary layer IR heating are both predicted to peak in Jezero crater. DD diameter, minimum height, and trajectory were studied showing (a) an average diameter of 29 m (or a median of 25 m) and a maximum and minimum diameter of 132 ± 63.4 and 5.6 ± 5.5 m; (b) an average minimum DD height of 231 m and a maximum minimum‐height of 872 m; and (c) the DD migration direction is in agreement with wind measurements. For all the cases, DDs decreased the UV irradiance, while at visible or near‐IR wavelengths both increases and decreases were observed. Contrary to the frequency of formation, these results indicate similar DD characteristics in average for the studied period. Plain Language Summary: Dust devils are dry, dusty convective vortices that play a key role in the dust cycle on Mars by lifting dust from the surface to the atmosphere. Parameters like the dust devil formation frequency or size characteristics are key to constrain their contribution to the planet's dust budget. Using observations made by the Radiation and Dust Sensor of the instrument Mars Environmental Dynamics Analyzer onboard Perseverance rover, we estimated the dust devil (DD) frequency for the full diurnal cycle in Jezero crater, Mars, during the first half of the Martian year. We find that between 1 and 3 DD per km−2 form every day, mainly around noon, and they become more frequent as spring advances to summer. The formation frequency is smaller than that estimated at the Spirit landing site but much greater than the values derived at InSight landing site, indicating a high variability in activity depending on location. When the DDs blocked the direct sunlight from reaching the sensor, we estimated their diameters to range between 5 and 130 m with an average of 29 m. In all detections, the presence of DDs resulted in a decrease of the measured UV radiation. Key Points: A dust devil frequency of occurrence of between 1.3 and 3.4 dust devils km−2 sol−1 was derived from MEDA‐RDS observations for the first 365 sols, displaying the maximum activity at around noon and increasing as we move from spring into summerWe find an average dust devil diameter of 29 m (or a median diameter of 25 m) and maximum and minimum diameters of 132 ± 63.4 m and 5.6 ± 5.5 mDust devil migration directions are in agreement with the MEDA background wind direction measurements [ABSTRACT FROM AUTHOR]