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The Mars2020 Perseverance Rover landed successfully on the Martian surface on the Jezero Crater floor (18.44°N, 77.45°E) at Martian solar longitude, Ls, ∼5° in February 2021. Since then, it has produced highly valuable environmental measurements with a versatile scientific payload including the MEDA (Mars Environmental Dynamics Analyzer) suite of environmental sensors. One of the MEDA systems is the PS pressure sensor system, which weighs 40 g and has an estimated absolute accuracy of better than 3.5 Pa and a resolution of 0.13 Pa. We present initial results from the first 414 sols of Martian atmospheric surface pressure observations by the PS, whose performance was found to meet its specifications. Observed sol‐averaged atmospheric pressures follow an anticipated pattern of pressure variation in the course of the advancing season and are consistent with data from other landing missions. The observed daily pressure amplitude varies by ∼2%–5 % of the sol‐averaged pressure, with absolute amplitude 10–35 Pa in an approximately direct relationship with airborne dust. During a regional dust storm, which began at Ls∼ 135°, the daily pressure amplitude roughly doubled. The daily pressure variations were found to be remarkably sensitive to the seasonal evolution of the atmosphere. In particular, analysis of the daily pressure signature revealed diagnostic information likely related to the regional scale structure of the atmosphere. Comparison of Perseverance pressure observations with data from other landers reveals the global scale seasonal behavior of Mars' atmosphere. Mars2020 Perseverance Rover successfully arrived on Mars in February 2021. It landed in an early Martian spring afternoon in a crater north of Mars' equator called Jezero crater. The rover is equipped with meteorological instruments that have so far produced extensive and valuable data for understanding the Martian atmosphere. One of the meteorological instruments is an accurate and precise pressure sensor. The pressure sensor has revealed large changes in the pressure over the seasons that are related to large changes in the actual mass of the Martian atmosphere. This is in line with seasonal pressure changes measured during previous Mars missions and can be explained as the condensation of the atmosphere onto the Martian poles and its subsequent sublimation. On a shorter time scale, the pressure sensor revealed complex pressure changes over a Martian day. These variations are thought to be related to atmospheric dust, whose ubiquitous nature is known to have a strong influence on the Martian climate. As the seasons progressed, the daily pressure variations morphed to exhibit different patterns likely related to the large‐scale regional changes in the atmosphere. Comparison of Perseverance pressure observations with other landers revealed the global nature of the atmosphere. The atmospheric pressure observations by Perseverance Rover have proved to be of excellent quality fulfilling expectationsJezero crater pressure exhibits significant differences to other Martian areas likely due to varying regional geography and solar forcingOverall, the diurnal and seasonal atmospheric pressure cycles at Jezero Crater follow an anticipated pattern of pressure variation The atmospheric pressure observations by Perseverance Rover have proved to be of excellent quality fulfilling expectations Jezero crater pressure exhibits significant differences to other Martian areas likely due to varying regional geography and solar forcing Overall, the diurnal and seasonal atmospheric pressure cycles at Jezero Crater follow an anticipated pattern of pressure variation

Martian global dust storms (GDS) can significantly affect the water cycle in the lower atmosphere (0−40 km). We compare the evolution of water vapor abundances, dust opacity and surface temperatures in the Southern Polar Region (SPR) during GDS years of MY25, MY28, and MY34 relative to years without GDS. During all GDS years, the vapor abundances decrease in the lower atmosphere in the SPR following the storm. Our results suggest that this decrease could be the result of disruption of the southward transport of vapor by atmospheric circulation. Alternatively, the decrease in vapor abundances could be caused by decreased desorption of vapor from the subsurface. This work presents comprehensive analysis of how water vapor in the Martian polar atmosphere reacts to large dust storms in different years. Measurements of water vapor, atmospheric dust, and surface temperatures collected by different spacecraft instruments in years with and without large dust storms are compared. These comparisons inform our understanding of how Martian water vapor is transported through the atmosphere and how it interacts with the surface. Large dust storms decrease the amount of water vapor in the southern polar region. This may indicate that the transport of vapor to the pole is reduced by the storms, or that dusty atmosphere cools the surface and reduces the amount of vapor released from the subsurface. Water vapor abundances over the Southern Polar Region of Mars are reduced following a global dust storm (GDS)The decrease in water vapor abundances could be caused by disruption of southward vapor transport by a GDSAlternatively, the decrease could be caused by changes in the surface‐atmosphere vapor exchange Water vapor abundances over the Southern Polar Region of Mars are reduced following a global dust storm (GDS) The decrease in water vapor abundances could be caused by disruption of southward vapor transport by a GDS Alternatively, the decrease could be caused by changes in the surface‐atmosphere vapor exchange

Recurring slope lineae (RSL) are dark linear markings on Mars that regrow annually and likely originate from the flow of either liquid water or granular material. Following the great dust storm (or planet‐encircling dust event, PEDE) of Mars year (MY) 34, Mars Reconnaissance Orbiter/High Resolution Imaging Science Experiment has seen many more candidate RSL than in typical Mars years. They have been imaged at more than 285 unique locations from August 2018 (when the atmosphere was clearing as the PEDE decayed) to August 2019, about half (157) of which are locations where RSL have not been documented previously. In MY34, 150 active RSL sites were identified in the southern middle latitudes (SML, ‐60° to ‐30°), whereas an average of 36 active sites were observed in each previous year (MY28–33). Post‐PEDE RSL are also present during southern summer over a wider range of latitude, slope aspect, and Ls(areocentric longitude of the sun) than in prior years. These RSL sites usually show evidence for recent dust deposition: obscuration of relatively dark areas, an overall brighter and redder surface than in prior years, and dust devil tracks, which indicate dust lifting by several mechanisms. We speculate that dust‐lifting processes may initiate and sustain RSL activity. The RSL may form from flows of dust (perhaps clumped) and/or sand that is destabilized by dust movement or directly mobilized by dust devils. If this is the case, then the otherwise puzzling recurrence and year‐to‐year variability of RSL activity can be at least partly explained. The dust replenishment varies from year to year, which could explain interannual variations in RSL activity. Recurring slope lineae (RSL) are puzzling active slope features on Mars that resemble seeping water. Following the great dust storm of 2018, many more candidate RSL were seen than in typical Mars years. These RSL sites usually show evidence for recent dust deposition. There are clear dust devil tracks in 73% of poststorm images in the southern middle latitudes in the summer, where and when dust devils are most active. The tracks indicate dust lifting, by several mechanisms. We suggest that dust‐lifting processes on steep slopes may initiate and sustain RSL formed from flows of dust (perhaps clumped) and/or sand that is destabilized by dust movement. The otherwise puzzling recurrence and year‐to‐year variability of RSL activity can be explained by variable yearly dust fallout. The origin of recurring slope lineae (RSL) on present‐day Mars has been controversial, including hypotheses with seeping water or dry granular flowsRecurring slope line were substantially more abundant following the planet‐encircling dust event in 2018Dust‐lifting processes present multiple possible mechanisms that can trigger downslope movement of dust and sand The origin of recurring slope lineae (RSL) on present‐day Mars has been controversial, including hypotheses with seeping water or dry granular flows Recurring slope line were substantially more abundant following the planet‐encircling dust event in 2018 Dust‐lifting processes present multiple possible mechanisms that can trigger downslope movement of dust and sand

In situ measurements of how air temperature near the surface responds to changing topography on other planets are rare. The Bagnold dunes were investigated by Mars Science Laboratory's Curiosity rover during its second winter in Gale crater on Mars. The effect of Bagnold dune slopes on the local microclimate air temperature, potential temperature, near‐surface lapse rate, and how they change the variability of short‐lived air temperature fluctuations is described. The oscillations with periods under 24 min are characterized using Fourier analysis. Comparing the sols during the Bagnold dunes exploration to a typical southern winter sol, we characterize the changes in temperature oscillations near the east facing High dune, the west facing Namib dune, as well as in the area between the dunes. Each of the regions had distinct signatures, with the west and east orientation of the dunes affecting the data. This manuscript describes the first in situ measurement of the observed effect of terrain slopes on the near‐surface air temperatures of another planet: (a) Air temperatures fluctuated due to convective activity and downslope topographic flows. (b) Both phenomena caused oscillations with different frequencies. (c) The proximity to dunes slopes changed the times of transition from stable to convective atmosphere depending on the orientation of the slopes. The proximity to a steep west face of Namib dune induced rapid oscillations during the evening downslope flow. Frequency regimes for convective versus topographic air temperature oscillations are found at Gale crater's surface layerUnique air temperature and inversion dynamics on Sols 1222‐1239 were caused by local slopes at the Namib duneAir temperature oscillation frequencies and regime transitions from neutral to convective are modulated by slopes grade and orientation