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Before the Perseverance rover landing, the acoustic environment of Mars was unknown. Models predicted that: (1) atmospheric turbulence changes at centimetre scales or smaller at the point where molecular viscosity converts kinetic energy into heat1, (2) the speed of sound varies at the surface with frequency2,3and (3) high-frequency waves are strongly attenuated with distance in CO2(refs. 2–4). However, theoretical models were uncertain because of a lack of experimental data at low pressure and the difficulty to characterize turbulence or attenuation in a closed environment. Here, using Perseverance microphone recordings, we present the first characterization of the acoustic environment on Mars and pressure fluctuations in the audible range and beyond, from 20 Hz to 50 kHz. We find that atmospheric sounds extend measurements of pressure variations down to 1,000 times smaller scales than ever observed before, showing a dissipative regime extending over five orders of magnitude in energy. Using point sources of sound (Ingenuity rotorcraft, laser-induced sparks), we highlight two distinct values for the speed of sound that are about 10 m s−1apart below and above 240 Hz, a unique characteristic of low-pressure CO2-dominated atmosphere. We also provide the acoustic attenuation with distance above 2 kHz, allowing us to explain the large contribution of the CO2vibrational relaxation in the audible range. These results establish a ground truth for the modelling of acoustic processes, which is critical for studies in atmospheres such as those of Mars and Venus.

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. 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. 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 Seasonal variations in irradiance at Mars' surface drive observed daily mean near‐surface air temperatures with some differences from models Thermal tides and long‐period traveling waves present a clear seasonal cycle with autumn and winter seasons more prone to variability Air temperatures underwent non‐seasonal changes near Jezero's delta, with strong daytime convection and nighttime gravity waves

This study presents, for the first time ever, occulting signals of the Global Navigation Satellite Systems (GNSSs) acquired at two polarizations from a Low Earth Orbiter, and it shows that they sense heavy precipitation. The data sets are obtained from early stages of the Radio Occultation and Heavy Precipitation experiment aboard the PAZ satellite, launched in February 2018 and activated in May 2018. Preliminary calibration algorithms are applied to remove other systematic effects, and the resulting vertical profiles of polarimetric phase shift observations are compared to precipitation information from other missions. The analysis of the data shows consistency between Radio Occultation and Heavy Precipitation experiment aboard the PAZ satellite polarimetric phase shift measurements and presence of hydrometeors, with strong signatures from heavy precipitation. The polarimetric measurements also capture vertical features consistent with the vertical structures of precipitation. When the satellites of the navigation systems (like GPS) set below the horizon, their signals can be used to measure temperature, pressure, and humidity of the atmosphere at different altitudes (an observation called radio occultation). For the first time, a satellite has collected these setting GPS signals at two polarizations, that is, separating two different orientations of the electromagnetic field (horizontal and vertical with respect to the receiving antenna). It is the Radio Occultation and Heavy Precipitation experiment aboard PAZ satellite, launched in February 2018 and activated in May 2018. Previous theoretical studies have shown that intense rain crossing the path of the GPS signals would introduce a delay of the horizontal component with respect to the vertical one. This study shows the analysis of the polarimetric delays, and it confirms that they are related to the presence of rain, in particular intense precipitation. The measurement of polarimetric delays at different altitudes is consistent with the presence of rain structures at different heights. No other technique captures profiles of both thermodynamics and hydrometeor content in intense rain phenomena, and therefore, the Radio Occultation and Heavy Precipitation experiment aboard the PAZ satellite data could provide a new tool to understand extreme precipitation, with potential to improve its difficult prediction. We present the first spaceborne GNSS radio occultation signals acquired at two polarizationsThe measured observables sense intense precipitation and capture its vertical structureNo other technique captures both thermodynamics and hydrometeor profiling in intense rain phenomena

Mars 2020 Mars Environmental Dynamics Analyzer (MEDA) instrument data acquired during half of a Martian year (Ls13°–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. 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. 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 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∼ 83 Both observations and modeling show turbulence during the first part of the night and around midnight Turbulence is produced by wind shear originating from the passage of an atmospheric bore wave related to downslope winds from the west rim

We study the diurnal cycle of rapid thermal fluctuations observed by the Mars Environmental Dynamics Analyzer, onboard the Perseverance rover at Jezero Crater, as a function of local time and season. In this context, rapid refers to periods between 15 min and half a second. Some insight is also provided into wind fluctuations that are the base for most of the existing theories on turbulent flows. The results expand the observations from previous Mars missions, namely Viking, Mars Pathfinder, and Phoenix, and they add to our knowledge of near‐surface fluctuations on Mars. (a) Probability distribution functions of the fluctuations are determined and found to have exponential tails. This means that models that represent the interaction within the environment and with the surface as a stochastic forcing need to account for the sudden events responsible for the exponential tails. (b) Power density spectra are calculated and show several dynamical regimes with different slopes associated to forcing, an intermediate regime, and a higher frequency regime. All change with time of the day. The results imply that the fastest regime is not a universal scenario for the temperature fluctuations near the surface. (c) The scale dependence of the fluctuations confirms the existence of intermittent outbursts associated to the slower fluctuations, possibly associated to the larger scale structures, and explains why the spectral density slopes do not follow Kolmogorov's law. Understanding the role of larger scale structures would help refine scaling theories of the near‐surface Martian atmosphere and its interactions with the surface. The Martian atmosphere is mostly driven by solar radiative forcing that also controls how it interacts with the surface. Atmospheric phenomena respond within seconds to years, but models can only resolve limited ranges of these time scales. This work explores how temperature fluctuates at time scales faster than what models typically resolve, and how this variability affects phenomena at the time scales that they resolve. The statistical properties of rapid environmental changes, or fluctuations, caused by solar forcing help us understand how the lowest atmosphere and surface evolve and interact. Theories that have been tested on Earth predicting how energy transfers or dissipates between the fast and slow dynamical regimes are explored here searching for rules that relate both regimes on another world. This work finds that fluctuations of air temperature and horizontal winds near the Martian surface do not follow probability distributions typical of normal random processes. The energy transfer rate is not consistent at scales faster than 10 s with a unique, or universal, rule relating fast to slow fluctuations. Finally, it suggests that this lack of universality is caused by intermittent disruptions through sudden large coherent structures, like convective vortices and waves, that influence how temperature dissipates. Probability Distribution functions for temperature fluctuations at Jezero Crater on the time scale of seconds have exponential tailsPower density spectra of temperature fluctuations find at least two dynamical regimes that evolve differently with time of the daySudden outbursts, likely associated to coherent structures, disrupt intermittently the rate of temperature dissipation to the smaller scales Probability Distribution functions for temperature fluctuations at Jezero Crater on the time scale of seconds have exponential tails Power density spectra of temperature fluctuations find at least two dynamical regimes that evolve differently with time of the day Sudden outbursts, likely associated to coherent structures, disrupt intermittently the rate of temperature dissipation to the smaller scales

Modeling and observations have long demonstrated that Martian dust storms strongly interfere with global circulation patterns and change the diurnal and semidiurnal pressure variability as well as oscillations with periods greater than one sol associated with planetary waves. As of early 2022, five Mars years of pressure data have been collected by the Curiosity Rover in Gale crater with the Rover Environmental Monitoring Station (REMS). A combination of signal filtering techniques is used to search for pressure signatures that might warn large‐scale dust storms reaching Gale. The analysis combines an exploration of changes in both baroclinic waves and thermal tides for the first time to our knowledge. Focusing on the periods preceding local opacity increases as detected by Curiosity's Mastcam observations, the pressure analysis shows changes in the coupling between the diurnal pressure tide and quasi‐diurnal Kelvin wave, as well as in the temporal evolution of baroclinic waves that are harbingers of the larger dust storms. Changes in the phasing between Kelvin waves and diurnal tides are found to be precursors for the growth phase of periods Z (defined here as Ls∼ 120°–160°), A (Ls∼ 190°–240°), and C (Ls∼ 300°–335°) dust storms. Changes in multi‐sol pressure oscillations also help predict the occurrence of A, B (Ls∼ 245°–295°), and C storms. The specific pressure oscillations preceding each storm period are likely to be signatures of the large‐scale circulation patterns that enable the growth and propagation of the storm fronts. There have been many efforts to characterize the impact of large‐scale dust storms on Mars's atmospheric circulation and wave activity. Surface pressure measurements made by the Curiosity Rover's Rover Environmental Monitoring Station (REMS) in Gale crater enable the study of some of these changes in global circulation patterns. Relatedly, numerical modeling and imaging by orbital spacecraft indicate that particular atmospheric circulation patterns—including particular combinations of waves—favor the growth and propagation of dust storms. Such patterns may be identified via their signature in surface pressure prior to the growth of the storm. This work presents several analyses that find equatorial waves preceding the growth of local dust opacity in Gale crater during the so‐called Z‐storm period in late southern winter and changes in baroclinic wave properties preceding the growth of opacity during other storm periods from early southern spring through late summer. Specific surface‐pressure oscillations in Gale crater precede increases in dust opacityDifferent dust seasons have different anticipatory behaviors depending on the dominant wave typeContinual analysis of pressure waves may be used to inform operations of landed craft on Mars Specific surface‐pressure oscillations in Gale crater precede increases in dust opacity Different dust seasons have different anticipatory behaviors depending on the dominant wave type Continual analysis of pressure waves may be used to inform operations of landed craft on Mars

We explore the potential role of clouds in moderating the nighttime temperature within Gale crater, as observed by the Rover Environmental Monitoring Station (REMS) instrument suite aboard the Curiosity rover. Just prior to aphelion, the decreasing trend in minimum daily temperature within Gale slows down. We investigate if this is due to increased formation of twilight and nighttime clouds, re‐radiating heat and reducing atmospheric and surface cooling. While diurnal analysis of REMS temperatures shows brief atmospheric warmings of 3–5 K post‐sunset during the occurrence of these clouds, an absence of similar warmings in the ground temperature measurements make it unlikely that clouds are the primary source. Seasonally, however, clouds that persist overnight could cause a warming of daily minimum surface temperatures in the Ls∼20°–50° season. This period can serve as a baseline and allow the potential effects of clouds to be more clearly discerned in the REMS temperature measurements. For this season, and in the peak of the aphelion cloud belt season, our modeled atmospheric energy budget shows a nocturnal decay signature of downward IR reflected and re‐emitted flux consistent with the presence and impact of clouds. The expected approximate exponential decay of this flux post‐sunset is damped more heavily in cloudier seasons than less cloudy or dusty seasons, suggesting formation and thickening of ice clouds as atmospheric nighttime temperatures cool. At Gale crater on Mars, we expect temperatures to be coldest at aphelion, the time when Mars is furthest from the Sun. Interestingly, we find that in some years, the lowest nighttime surface temperatures do not steadily decline during the period approaching aphelion but, rather, show a short‐lived reversal of this trend, becoming slightly warmer for a few weeks prior to aphelion. Analysis of surface and air temperature data from the Curiosity rover during this period, along with twilight imagery from the surface, and infrared measurements from orbit, points to the possibility of nighttime clouds acting as a means of warming the surface. These clouds only form around aphelion, perhaps explaining the unusual seasonal temperatures during this period. Nighttime warmings of the atmosphere and surface are detected and hypothesized as thermal signatures of cloudsThe range of areocentric longitudes where the warmings are observed coincides with the visual observation of cloudsAn energy balance model shows consistency with nocturnal evolution of reflected and re‐emitted radiation from clouds Nighttime warmings of the atmosphere and surface are detected and hypothesized as thermal signatures of clouds The range of areocentric longitudes where the warmings are observed coincides with the visual observation of clouds An energy balance model shows consistency with nocturnal evolution of reflected and re‐emitted radiation from clouds