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The Mars Regional Atmospheric Modeling System ( MRAMS ) and a nested simulation of the Mars Weather Research and Forecasting model ( MarsWRF ) are used to predict the local meteorological conditions at the Mars 2020 Perseverance rover landing site inside Jezero crater (Mars). These predictions are complemented with the COmplutense and MIchigan MArs Radiative Transfer model ( COMIMART ) and with the local Single Column Model ( SCM ) to further refine predictions of radiative forcing and the water cycle respectively. The primary objective is to facilitate interpretation of the meteorological measurements to be obtained by the Mars Environmental Dynamics Analyzer ( MEDA ) aboard the rover, but also to provide predictions of the meteorological phenomena and seasonal changes that might impact operations, from both a risk perspective and from the perspective of being better prepared to make certain measurements. A full diurnal cycle at four different seasons ( L s   0 ∘ , 90 ∘ , 180 ∘ , and 270 ∘ ) is investigated. Air and ground temperatures, pressure, wind speed and direction, surface radiative fluxes and moisture data are modeled. The good agreement between observations and modeling in prior works [Pla-Garcia et al. in Icarus 280:103–113, 2016 ; Newman et al. in Icarus 291:203–231, 2017 ; Vicente-Retortillo et al. in Sci. Rep. 8(1):1–8, 2018 ; Savijärvi et al. in Icarus, 2020 ] provides confidence in utilizing these models results to predict the meteorological environment at Mars 2020 Perseverance rover landing site inside Jezero crater. The data returned by MEDA will determine the extent to which this confidence was justified.

NASA’s Mars 2020 (M2020) rover mission includes a suite of sensors to monitor current environmental conditions near the surface of Mars and to constrain bulk aerosol properties from changes in atmospheric radiation at the surface. The Mars Environmental Dynamics Analyzer (MEDA) consists of a set of meteorological sensors including wind sensor, a barometer, a relative humidity sensor, a set of 5 thermocouples to measure atmospheric temperature at ∼1.5 m and ∼0.5 m above the surface, a set of thermopiles to characterize the thermal IR brightness temperatures of the surface and the lower atmosphere. MEDA adds a radiation and dust sensor to monitor the optical atmospheric properties that can be used to infer bulk aerosol physical properties such as particle size distribution, non-sphericity, and concentration. The MEDA package and its scientific purpose are described in this document as well as how it responded to the calibration tests and how it helps prepare for the human exploration of Mars. A comparison is also presented to previous environmental monitoring payloads landed on Mars on the Viking, Pathfinder, Phoenix, MSL, and InSight spacecraft.

The Mars Science Laboratory spacecraft, containing the Curiosity rover, was launched to Mars on 26 November 2011, and for most of the 253-day, 560-million-kilometer cruise to Mars, the Radiation Assessment Detector made detailed measurements of the energetic particle radiation environment inside the spacecraft. These data provide insights into the radiation hazards that would be associated with a human mission to Mars. We report measurements of the radiation dose, dose equivalent, and linear energy transfer spectra. The dose equivalent for even the shortest round-trip with current propulsion systems and comparable shielding is found to be 0.66 ± 0.12 sievert.

Saturn’s moon Titan has a dense nitrogen-rich atmosphere, with methane as its primary volatile. Titan’s atmosphere experiences an active chemistry that produces a haze of organic aerosols that settle to the surface and a dynamic climate in which hydrocarbons are cycled between clouds, rain and seas. Titan displays particularly energetic meteorology at equinox in equatorial regions, including sporadic and large methane storms. In 2009 and 2010, near Titan’s northern spring equinox, the Cassini spacecraft observed three distinctive and short-lived spectral brightenings close to the equator. Here, we show from analyses of Cassini spectral data, radiative transfer modelling and atmospheric simulations that the brightenings originate in the atmosphere and are consistent with formation from dust storms composed of micrometre-sized solid organic particles mobilized from underlying dune fields. Although the Huygens lander found evidence that dust can be kicked up locally from Titan’s surface, our findings suggest that dust can be suspended in Titan’s atmosphere at much larger spatial scale. Mobilization of dust and injection into the atmosphere would require dry conditions and unusually strong near-surface winds (about five times more than estimated ambient winds). Such strong winds are expected to occur in downbursts during rare equinoctial methane storms—consistent with the timing of the observed brightenings. Our findings imply that Titan—like Earth and Mars—has an active dust cycle, which suggests that Titan’s dune fields are actively evolving by aeolian processes.

The Radiation Assessment Detector (RAD) on the Mars Science Laboratory (MSL) is an energetic particle detector designed to measure a broad spectrum of energetic particle radiation. It will make the first-ever direct radiation measurements on the surface of Mars, detecting galactic cosmic rays, solar energetic particles, secondary neutrons, and other secondary particles created both in the atmosphere and in the Martian regolith. The radiation environment on Mars, both past and present, may have implications for habitability and the ability to sustain life. Radiation exposure is also a major concern for future human missions. The RAD instrument combines charged- and neutral-particle detection capability over a wide dynamic range in a compact, low-mass, low-power instrument. These capabilities are required in order to measure all the important components of the radiation environment. RAD consists of the RAD Sensor Head (RSH) and the RAD Electronics Box (REB) integrated together in a small, compact volume. The RSH contains a solid-state detector telescope with three silicon PIN diodes for charged particle detection, a thallium doped Cesium Iodide scintillator, plastic scintillators for neutron detection and anti-coincidence shielding, and the front-end electronics. The REB contains three circuit boards, one with a novel mixed-signal ASIC for processing analog signals and an associated control FPGA, another with a second FPGA to communicate with the rover and perform onboard analysis of science data, and a third board with power supplies and power cycling or “sleep”-control electronics. The latter enables autonomous operation, independent of commands from the rover. RAD is a highly capable and highly configurable instrument that paves the way for future compact energetic particle detectors in space.

NASA’s Perseverance rover’s Mars Environmental Dynamics Analyzer is collecting data at Jezero crater, characterizing the physical processes in the lowest layer of the Martian atmosphere. Here we present measurements from the instrument’s first 250 sols of operation, revealing a spatially and temporally variable meteorology at Jezero. We find that temperature measurements at four heights capture the response of the atmospheric surface layer to multiple phenomena. We observe the transition from a stable night-time thermal inversion to a daytime, highly turbulent convective regime, with large vertical thermal gradients. Measurement of multiple daily optical depths suggests aerosol concentrations are higher in the morning than in the afternoon. Measured wind patterns are driven mainly by local topography, with a small contribution from regional winds. Daily and seasonal variability of relative humidity shows a complex hydrologic cycle. These observations suggest that changes in some local surface properties, such as surface albedo and thermal inertia, play an influential role. On a larger scale, surface pressure measurements show typical signatures of gravity waves and baroclinic eddies in a part of the seasonal cycle previously characterized as low wave activity. These observations, both combined and simultaneous, unveil the diversity of processes driving change on today’s Martian surface at Jezero crater.Meteorology measurements from NASA’s Perseverance rover on Mars reveal a diversity of processes at work in the atmospheric boundary layer at Jezero crater over a range of temporal scales.

Still delivering ESA's Venus Express probe has been in orbit since April 2006. Eight research papers in this issue present new results from the mission, covering the atmosphere, polar features, interactions with the solar wind and the controversial matter of venusian lightning. Håkan Svedham et al . open the section with a review of the similarities and (mostly) differences between Venus and its 'twin', the Earth. Andrew Ingersoll considers the latest results, and also how the project teams plan to make the most of the probe's remaining six years of life. Venus' mesosphere is a transition region between the retrograde super rotation at the top of the thick clouds and the solar-antisolar circulation in the thermosphere. The mesospheric distributions of HF, HCl, H 2 O and HDO are reported, and an unexpected extensive layer of warm air at altitudes 90–120 km on the nightside is found. Venus has thick clouds of H 2 SO 4 aerosol particles extending from altitudes of 40 to 60 km. The 60–100 km region (the mesosphere) is a transition region between the 4 day retrograde superrotation at the top of the thick clouds and the solar–antisolar circulation in the thermosphere (above 100 km), which has upwelling over the subsolar point and transport to the nightside 1 , 2 . The mesosphere has a light haze of variable optical thickness, with CO, SO 2 , HCl, HF, H 2 O and HDO as the most important minor gaseous constituents, but the vertical distribution of the haze and molecules is poorly known because previous descent probes began their measurements at or below 60 km. Here we report the detection of an extensive layer of warm air at altitudes 90–120 km on the night side that we interpret as the result of adiabatic heating during air subsidence. Such a strong temperature inversion was not expected, because the night side of Venus was otherwise so cold that it was named the ‘cryosphere’ above 100 km. We also measured the mesospheric distributions of HF, HCl, H 2 O and HDO. HCl is less abundant than reported 40 years ago 3 . HDO/H 2 O is enhanced by a factor of ∼2.5 with respect to the lower atmosphere, and there is a general depletion of H 2 O around 80–90 km for which we have no explanation.

The Radiation Assessment Detector (RAD), on board the Mars Science Laboratory (MSL) rover Curiosity, measures the energetic charged and neutral particles and the radiation dose rate on the surface of Mars. Although charged and neutral particle spectra have been investigated in detail, the electron and positron spectra have not been investigated yet. The reason for that is that they are difficult to separate from each other and because of the technical challenges involved in extracting energy spectra from the raw data. We use GEANT4 to model the behavior of the RAD instrument for electron/positron measurements. We compare Planetocosmics predictions for different atmospheric pressures and different modulation parameters Φ with the obtained RAD electron/positron measurements. We find that the RAD electron/positron measurements agree well with the spectra predicted by Planetocosmics. Both RAD measurements and Planetocosmics simulation show a dependence of the electron/positron fluxes on both atmospheric pressure and solar modulation potential.

The Mars Science Laboratory rover Curiosity, operating on the surface of Mars, is exposed to radiation fluxes from above and below. Galactic Cosmic Rays travel through the Martian atmosphere, producing a modified spectrum consisting of both primary and secondary particles at ground level. These particles produce an upward directed secondary particle spectrum as they interact with the Martian soil. Here we develop a method to distinguish the upward and downward directed particle fluxes in the Radiation Assessment Detector (RAD) instrument, verify it using data taken during the cruise to Mars, and apply it to data taken on the Martian surface. We use a combination of Geant4 and Planetocosmics modeling to find discrimination criteria for the flux directions. After developing models of the cruise phase and surface shielding conditions, we compare model‐predicted values for the ratio of upward to downward flux with those found in RAD observation data. Given the quality of available information on Mars Science Laboratory spacecraft and rover composition, we find generally reasonable agreement between our models and RAD observation data. This demonstrates the feasibility of the method developed and tested here. We additionally note that the method can also be used to extend the measurement range and capabilities of the RAD instrument to higher energies. Plain Language Summary The MSL rover Curiosity is exposed to energetic particles from above and below on the Martian surface. Particles enter the Martian atmosphere from above and travel through it until they reach the ground. Particles lose energy and can produce secondary particles while passing through the atmosphere, resulting in an energy distribution on ground level that is different from that on the top of the atmosphere. The resulting particles produce an upward directed particle distribution in the soil. We develop a method to distinguish the upward and downward particle fluxes in the RAD instrument, verify it using data taken during the cruise to Mars, and apply it to data taken on the Martian surface. We use a combination of models to find criteria for discriminating the flux directions. After developing models of the cruise phase and surface shielding conditions, we compare simulated values for the ratio of upward to downward flux with those found in observation data. We find generally reasonable agreement between our models and RAD observation data. This demonstrates the feasibility of the method developed and tested here. The method can also be used to extend the measurement range and capabilities of the RAD instrument to higher energies. Key Points We model the radiation environment during the MSL cruise phase and on the Martian surface We obtain the particle energy spectra at the RAD instrument for both scenarios After developing a method to distinguish between upward and downward fluxes, we apply the method both to simulation data and to data taken by the RAD instrument during the cruise phase and on the surface