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Using near-infrared observations of Neptune from the Keck and Lick Observatories, and the Hubble Space Telescope in combination with amateur datasets, we calculated the drift rates of prominent infrared-bright cloud features on Neptune between 2018 and 2021. These features had lifespans of $\sim 1$ day to $\geq$1 month and were located at mid-latitudes and near the south pole. Our observations permitted determination of drift rates via feature tracking. These drift rates were compared to three zonal wind profiles describing Neptune's atmosphere determined from features tracked in H band (1.6 $\mu m$), K' band (2.1 $\mu m$), and Voyager 2 data at visible wavelengths. Features near $-70 \deg$ measured in the F845M filter (845nm) were particularly consistent with the K' wind profile. The southern mid-latitudes hosted multiple features whose lifespans were $\geq$1 month, providing evidence that these latitudes are a region of high stability in Neptune's atmosphere. We also used HST F467M (467nm) data to analyze a dark, circumpolar wave at $- 60 \deg$ latitude observed on Neptune since the Voyager 2 era. Its drift rate in recent years (2019-2021) is $4.866 \pm 0.009 \deg $/day. This is consistent with previous measurements by Karkoschka (2011), which predict a $4.858 \pm 0.022 \deg$/day drift rate during these years. It also gained a complementary bright band just to the north., Comment: 29 pages, 13 figures, accepted to Icarus

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, $L_s$, $\sim$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 grams 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 diurnal pressure amplitude varies by $\sim$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 $L_s~135^\circ$ the diurnal pressure amplitude roughly doubles. The diurnal pressure variations were found to be remarkably sensitive to the seasonal evolution of the atmosphere. In particular analysis of the diurnal pressure signature revealed diagnostic information likely related to the regional scale structure of the atmosphere. Comparison of Perseverance pressure observations to data from other landers reveals the global scale seasonal behaviour of Mars’ atmosphere.

The discontinuity/disruption is a recurrent atmospheric wave observed to propagate during decades at the deeper clouds of Venus (47-56 km above the surface), while its absence at the top of the clouds (~70 km) suggests that it might dissipate at the upper clouds and contribute to the puzzling atmospheric superrotation through wave-mean flow interaction.Thanks to a campaign of ground-based observations performed in coordination with JAXA's Akatsuki mission since December 2021 until July 2022, we aimed to undertake the longest uninterrupted monitoring of the cloud discontinuity up to date to obtain a pioneering long-term characterization of its main properties and better constrain its recurrence and lifetime. The dayside upper, middle and nightside lower clouds were studied with images taken with suitable filters acquired by Akatsuki/UVI, amateur observers and NASA's IRTF/SpeX, respectively. Hundreds of images were inspected in search of discontinuity events and to measure properties like its dimensions, orientation or rotation period.We succeeded in tracking the discontinuity at the middle clouds during 109 days without interruption. The discontinuity exhibited properties nearly identical to measurements in 2016 and 2020, with an orientation of 91º±8º, length of 4100±800, width of 500±100 km and a rotation period of 5.11±0.09 days. Ultraviolet images during 13-14 June 2022 suggest that we have witnessed for the first time a manifestation of the discontinuity at the top of the clouds during ~21 hours, facilitated by an altitude change in the critical level for this wave due to slower zonal winds.

Four surface stations (rovers Curiosity, Perseverance, and Zhurong, and the Insight platform) were operating on Mars along Martian Year 36 (7 February 2021 – 26 December 2022), all them equipped with a suite of meteorological sensors and cameras. In addition, eight orbiters are currently studying the planet from different perspectives and instruments. To help to interpret and put in context the meteorological measurements at the surface by these stations, we present here a study of the atmospheric disturbances, at the planetary and synoptic scales, based on images of Mars obtained from cameras onboard Mars Express and Mars Reconnaissance Orbiter [1, 2]. We report on the properties of the disturbances that evolved at the edge of the North Polar Cap (latitudes ~ 40°N to 70°N) during the springtime season in the northern hemisphere. These are dust storms and synoptic-scale cloud systems with arc, frontal, irregular and spiral shapes, typically growing from the baroclinic instabilities in the intense eastward jet present in this epoch of the Martian year. We also report on the evolution of the aphelion cloud belt (Ls ~ 0° – 180°), including among other phenomena the recurrent annular-double cyclone (Ls ~ 125°) and the cloud development at Hellas basin (Ls ~ 145° – 300°). Finally, we present an analysis of the dust storms that evolved at different latitudes, concentrating in particular in the regional storm that evolved over Perseverance in early January 2022. References[1] Sánchez-Lavega, A. et al., Icarus 299, 194-205 (2018)[2] Bell III, J. F. et al., J. Geophys. Res. Planets 114, E003315, 1-41 (2009)

We use data from the MEDA instrument on Mars 2020 to study the evolution of atmospheric and surface temperatures at Jezero. The measurements correspond to four height levels from the surface to ~40 m and together they allow us to examine multiple aspects of the near-surface meteorology at Jezero. We extend the analysis of near-surface temperatures of Munguira et al. (JGR:Planets 2023), which covered the period from Ls 13º to Ls 203º, over a full Martian year. We show the seasonal evolution of temperatures, including temperature fluctuations and thermal gradients, which are affected by the properties of the terrain traversed by Perseverance. We will focus on a physical description of the thermal processes that take place in the Convective Boundary Layer at Jezero. We compare near-surface temperatures with the atmospheric opacity around-the-clock retrieved by Smith et al. (2022) and with daily averages of optical depth measured by MastCam-Z (Bell et al. 2022). After Ls 203º, atmospheric waves coming across Jezero predicted by atmospheric models are expected to contribute to shaping temperatures producing thermal oscillations on time-scales of a few sols. This effect is accompanied by an enhanced variability of atmospheric opacity and both effects contribute to produce a higher variability on temperatures. References:[1] Munguira, A. et al. (2023). Near Surface Atmospheric Temperatures at Jezero from Mars 2020 MEDA Measurements. JGR: Planets.[2] Smith, M.D. et al. (2022). Diurnal and Seasonal Variations of Aerosol Optical Depth Observed by MEDA/TIRS at Jezero Crater, Mars. In Seventh international workshop on the Mars atmosphere: Modelling and observations (pp. 14-17).[3] Bell, J.F. et al. (2022). Geological, multispectral, and meteorological imaging results from the mars 2020 perseverance rover in jezero crater. Science Advances, 8 (47), eabo4856. doi: 10.1126/sciadv.abo485

After one year of surface operations at Jezero, the MEDA meteorological sensors have captured the signals produced by the close approach of hundreds of vortices and dust devils over different seasons and terrains. Here we update findings on the vortex and Dust Devils published in Hueso et al. (JGR: Planets, 2023). That work analyzed MEDA data from spring to early autumn identifying vortices as pressure drops and later characterizing them from the ensemble of MEDA measurements. In this updated analysis we show that, in winter, declining surface temperatures and smaller vertical gradients result in a wane of vortex activity. This decreased activity affects more the frequency of intense vortices (Δp >1.5 Pa) without showing a stiff decay in the total number of vortices (Δp>0.5 Pa). In this contribution we concentrate on the specific aspects of the thermodynamics of the vortices from temperature measurements obtained by MEDA that characterize the vertical thermal gradient at the time of the vortex passage. In addition, when vortices approach the rover closely in a favorable geometry (coming from the front of the vortex) we measure the increased temperatures inside the vortex. We also explore the increased nighttime vortex activity found on some sols, when pressure drops equivalent to those created by daytime vortices appear in the early morning before sunrise, with clusters of nighttime activity in winter and early spring.

The Mars Environmental Dynamics Analyzer (MEDA) instrument, on board the NASA’s Mars 2020 Perseverance rover, includes a number of sensors to characterize the Martian atmosphere. One of this 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◦) 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◦ to 150◦ (cloudy period), an dust from Ls 150◦-262◦. A total of 161 twilights were analyzed in the cloudy period using a radiative transfer code and we found: i) signatures of clouds/hazes in the signals in the 58 % of the twilights; ii) most of the clouds had altitudes between 40-50 km, suggesting water ice composition, and had particle sizes between 0.6 and 2 μm; iii) the cloud activity at sunrise is slightly higher that at sunset, likely due to the differences in temperature; iv) the time period with more cloud detections and with the greatest cloud opacities is during Ls 120◦-150◦; and v) a notable decrease in the cloud activity around the 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.

Anghel, S., et al., The increase in detector sensitivity and availability in the past three decades has allowed us to derive knowledge of the meteoroid flux and impact energy into the Earth's atmosphere. We present the multi-instrument detected 2018 December 22 fireball over Western Pyrenees, and compare several techniques aiming to obtain a reliable method to be used when measuring impacts of similar scale. From trajectory data alone, we found a bulk density of 3.5 g cm-3 to be the most likely value for the Pyrenean meteoroid. This allowed to further constrain the dynamic mass, which translated into a kinetic energy of 1 ton TNT (4.184 × 109 J). For the second energy derivation, via the fireball's corrected optical radiation, we obtained a more accurate empirical relation measuring well-studied bolides. The result approximates to 1.1 ton TNT, which is notably close to the nominal dynamic result, and agrees with the lower margin of the seismic-based energy estimation, yet way lower than the infrasound estimate. Based on the relation derived in this study, we consider the nominal estimate from both the dynamic and photometric methods to be the most accurate value of deposited energy (1 ton TNT). We show that the combination of these two methods can be used to infer the meteoroid density. Among the methods presented in this paper, we found that the optical energy is the most reliable predictor of impact energy near the ton TNT-scale., S. Anghel and D. A. Nedelcu were supported by a grant of the Romanian Ministry of Research and Innovation, CCCDI - UEFISCDI, project number PN-III-P1-1.2-PCCDI-2017-0226/16PCCDI/2018, within PNCDI III. EP-A and JMT-R acknowledge funding from PGC2018-097374-B-I00 (MCI-AEI-FEDER, EU). M. Birlan work was partly supported by SEEING-IEA CNRS program. R. Hueso and A. Sánchez-Lavega were supported by Diputación Foral de Bizkaia and Gobierto Vasco IT1366-19.

The Visual Monitoring Camera (VMC) is a small camera onboard Mars Express, initially intended to provide visual confirmation of the separation of the Beagle 2 lander. In 2007, a few years after the end of its original mission, VMC was turned on again to obtain full-disk images of Mars for outreach purposes (Ormston et al., 2011). As VMC obtained more images, the scientific capabilities of the camera became evident (Sánchez-Lavega et al., 2018), and finally the small camera was upgraded to be a new scientific instrument, with an agreement between the European Space Agency (ESA) and the University of the Basque Country (Spain; UPV/EHU). In this work we describe the calibration and technical efforts that are allowing us to maximize the scientific output from this small camera. Figure 1. Image of VMC before launch (left) and scheme from the Flight User Manual (right) VMC is also called the Mars webcam, as it is similar to a typical webcam of the 2000s. The sensor has a a 640x480 pixel array, and a Field of View (FOV) of 30ºx40º. This wide FOV, together with the elliptical orbit of Mars Express, enables full-disk observations from apocenters, which are the most common product of VMC. It is also possible to use this wide FOV to image large sections of the limb, and therefore monitor the occurrence of high altitude aerosols, as shown by Sánchez-Lavega et al. (2018). Figure 2. Full disk of Mars as seen by VMC. Operations Since 2018 VMC operations follow a similar routine as those used for other science instruments. The Science Ground Segment takes care of the Medium Term Planning (MTP) following the inputs from the science team. The science team performs the Short Term Planning (STP). Fig. 3 shows a typical VMC observation, which consists of a default image, followed by one to several loops of 6 images that use a set of predefined exposures. The exposure times are set to maximize the dynamic range of the final science products obtained by combining the individual images. Figure 3. Scheme of a typical VMC observation. Calibration of images The images are calibrated following the standard scheme of subtracting a dark current and dividing by a flatfield image. The flat field correction is much more relevant than the dark correction in the quality of the final images after calibration. No onground calibration is known for VMC, therefore the dark current and flat-field corrections used are based only on in-flight observations. The dark was obtained by pointing VMC to the sky, specifically the area of Eridanus, where few bright stars are present. The flat-field was created using dark-corrected images of flat portions of Mars that were well and uniformly illuminated, as free as possible from large structures, and as flat as possible. Calibrated images are routinely archived at ESA’s Planetary Science Archive (PSA), as described by Ravanis et al. (2020) Figure 4. VMC dark (left) and flat (right). Geometry The original documents indicate the design parameters for the orientation of VMC in the reference frame of MEX, and for the pixel resolution (iFOV). However, the accurate parameters once VMC was mounted on MEX were never measured on the ground. In addition to this, we find that the timestamp of images suffers a random shift of a few seconds. As a result, we have 5 free parameters: 3 Euler angles for the attitude relative to the MEX reference frame; the pixel resolution (iFOV); and the shift in time from the actual timestamp to the labeled timestamp. In order to determine the attitude and iFOV of VMC relative to Mars Express, we used images showing stars. Many of these observations covered the stars of the constellation of Orion, because several suitable stars are present in that region of the sky. During these observations the spacecraft maintains a fixed attitude, therefore, the time related uncertainty is not present and only 4 free parameters remain: 3 Euler angles, and the pixel size. These parameters are shown in table 1. Table 1. VMC geometric parameters as given by the Flight User Manual (FUM) and calibrated values. The shift in time was estimated from observations showing Phobos. The relative speed of Phobos as seen from Mars Express is high, and therefore it is possible to use its position as an accurate clock. We find that our images are usually obtained between 6 and 13 seconds before the labeled time, but we find random variations. Subtracting 10 seconds is considered a good strategy in most cases, but this uncertainty remains as a limitation. Figure 5. VMC image showing the stars of Orion (left), and Phobos in front of Mars (right). Red circles represent the expected position before calibration. Green circles are the expected positions according to the new calibration. Conclusions Within the expectable limitations, the performance of this new instrument is very good and VMC is enabling novel science results and techniques (e.g. Hernández-Bernal et al. 2021). This is in part because VMC provides some capabilities that are not common among instruments in orbital planetary missions. Even with no on-ground calibration available, it has been possible to calibrate the camera, both photometrically and geometrically. Some hardware limitations remain, and others have been partially overcome with specially developed operational strategies. References Hernández‐Bernal et al. (2021). A Long‐Term Study of Mars Mesospheric Clouds Seen at Twilight Based on Mars Express VMC Images. Ormston et al. (2011) An ordinary camera in an extraordinary location: Outreach with the Mars Webcam. Ravanis et al. (2020). From engineering to science: Mars Express Visual Monitoring Camera's first science data release. Sánchez-Lavega et al. (2018). Limb clouds and dust on Mars from images obtained by the Visual Monitoring Camera (VMC) onboard Mars Express.

Introduction The Great Red Spot of Jupiter (GRS) is the largest and longest-lived anticyclone in the Solar System. First observed probably in the XVII century, it is one of the most remarkable dynamical phenomena in any known atmosphere. The structure, coloration and dynamical behavior of the Jovian anticyclone are severely affected by the formation and evolution of the GRS upper hazes, making them a relevant field of study. The distinctive reddish color of the GRS (see Figure 1) is due to the nature and vertical distribution of the hazes over it. Carlson et al. (2016) proposed a possible chromophore to explain the GRS coloration: the products from photolyzed ammonia reacting with acetylene. Sromovsky et al. (2017) showed that this species was able to explain the reddish colorations all over the planet, despite being of very different intensity. This chromophore must be located on top of the tropospheric haze, in the so called “crème brûlée” model. Anguiano-Arteaga et al. (2021) performed a radiative transfer analysis that showed the existence of a stratospheric haze that could be compatible with the chromophore agent proposed by Carlson et al. (2016), although their study also suggested another chromophore located below that, in the upper tropospheric levels. However, every single color in the region shown in Figure 1 was also explained with those two chromophores. In a recent paper (Anguiano-Arteaga et al., 2022) we find that the results of Anguiano-Arteaga et al. (2021) remain valid at least from 2015 to 2021, and no major temporal variations are expected in years close to such time span. Figure 1. Map showing Jupiter’s Great Red Spot in December 2016. The RGB images are constructed from HST/WFC3 images with R=F631N, G=F502N and B=F395N. Image taken from Anguiano-Arteaga et al. (2022). Vertical structure of the GRS Images taken in filters sensitive to the altitude of the clouds and hazes show that the cloud top of the GRS is higher than its environment. The altitude of the hazes plays a major role in the coloration and dynamics. For example, in the scheme proposed by Carlson et al. (2016) material in the GRS raises to upper pressure levels and undergoes photochemical reactions that lead to the creation of the coloring agent. The amount of material high in the atmosphere would be then a fundamental factor to determine the production rate of chromophore species. Radiative transfer analyses give some insight on the altitude of the clouds and hazes. In Figure 2, we show maps of cloud top effective altitudes obtained from radiative transfer spectral modeling, as shown in Anguiano-Arteaga et al. (2021, 2022). However, radiative transfer analyses cannot provide some important information on the hazes, such as chromophore production rates or timescales of the undergoing atmospheric processes (e.g., coagulation, condensation and sedimentation). Because of this, microphysical considerations should be also taken into account in order to get a more complete description of the nature, structure and evolution of the hazes. Figure 2. Map of the GRS area in December 2016 showing the pressure levels (in mbar) where the optical depth at 900 nm equals unity. This map is interpreted as the cloud top effective altitude. Microphysical study In this work, we perform microphysical simulations of the GRS hazes in the stratosphere and upper troposphere (P < 500 mbar). For this purpose, we develop a 1-D numerical code that takes into account the effects of particle sedimentation, coagulation, eddy diffusion and aerosol growth by molecular condensation. We report here results on the particle size distribution as a function of altitude, together with aerosol concentrations and timescale analysis regarding different microphysical processes. This constrains the mass production rates required to explain the chromophore model and hence serves as a test for any given proposed candidate. The results are interpreted according to prior findings following radiative transfer analysis on the GRS. References - Anguiano-Arteaga, A., Pérez-Hoyos, S., Sánchez-Lavega, A., Sanz-Requena, J. F., & Irwin, P. G. J. (2021). Vertical distribution of aerosols and hazes over Jupiter's Great Red Spot and its surroundings in 2016 from HST/WFC3 imaging. J. Geophys. Res. Planets., 126, e2021JE006996 https://doi.org/10.1029/2021JE006996 - Anguiano-Arteaga, A., Pérez-Hoyos, S., Sánchez-Lavega, A., Sanz-Requena, J. F., & Irwin, P. G. J. (2022). Temporal variations in vertical cloud structure of Jupiter’s Great Red Spot, its surroundings and oval BA from HST/WFC3 imaging. Submitted to J. Geophys. Res. Planets. - Carlson, R.W., Baines, K.H., Anderson, M.S., Filacchione, G., & Simon, A.A. (2016). Chromophores from photolyzed ammonia reacting with acetylene: Application to Jupiter’s Great Red Spot. Icarus, 274, 106-115. https://doi.org/10.1016/j.icarus.2016.03.008 - Sromovsky, L.A., Baines, K.H., Fry, P.M., & Carlson, R.W. (2017). A possibly universal red chromophore for modeling color variations on Jupiter. Icarus, 291, 232-244. https://doi.org/10.1016/j.icarus.2016.12.014

The aim of this investigation is to carry out a study of the variability of nocturnal atmospheric turbulence at Jezero crater supported by modeling effort and monitored by MEDA. The rapid turbulent kinetic energy (hereafter TKE), wind and pressure fluctuations observed during nighttime both with modeling and MEDA is a clear indicator of nocturnal turbulence. The origin of this nocturnal turbulence is explored with MRAMS and, as opposed to Gale crater, low evidence of significant gravity waves activity during the whole period studied was found. On the contrary, the nighttime turbulence at Jezero crater could be shear driven and may be explained due to an enhanced mechanical turbulence produced by increasingly strong shear (onset of a strong low-level jet) at the nocturnal inversion interface. As the nocturnal inversion develops, the winds above become decoupled from the surface and the decrease in friction produces a net acceleration [refs 4, 5, 6, 7]. Once the critical Richardson Number is reached (Ri ∼< 0.25, Figure 3), shear instabilities can mix warmer air aloft down to the surface [refs 8, 9, 10]. 1. Introduction The Mars 2020 Perseverance rover landed in Mars in February 2021 at 18.44°N 77.45°E within and near the northwest rim of Jezero crater. The MEDA weather station is aboard Perseverance rover [ref 1]. 2. MRAMS mesoscale simulations MRAMS was applied to Mars 2020 landing site region using nested grids with a spacing of 330 meters on the innermost grid that is centered over the landing site [ref 2]. 3. Nighttime turbulence modeled with MRAMS The effect of subgrid-scale eddies is captured within MRAMS via a prognostic TKE (Figure 1) equation [ref 3]. MRAMS shows a peak in TKE during the afternoon, which is consistent with the modeled high-frequency variations in air temperatures [Figure 3 of ref 2]. The sudden increase in air temperature during the evenings [Figure 3 of ref 2] at the onset of radiative cooling is produced by mechanically driven turbulence since the atmosphere is stable and non-convective in the evening. The model does often show small increases of TKE during the night (Figure 1), especially during Ls=180º (corresponding to Mars 2020 sol 362) and some during Ls 105 and Ls 160 (corresponding to Mars 2020 sols 216 and 326), that could be associated with the turbulent aspects of the nighttime dynamical flows when compared with nearby locations with more flat topography. During the late evening and night, MRAMS is resolving thermal variations [2, Figure 3] and does often show small increases of TKE at that time (Figure 1). The rapid air temperature fluctuations modeled at night in all seasons is indicative of nocturnal turbulence. There is low evidence of significant wave activity during the whole period studied and only some gravity waves were found. The nighttime turbulence could be attributed to shear driven turbulence and may be explained due to an enhanced mechanical turbulence driven by increasingly strong shear, with the onset of the nocturnal low-level jet, at the nocturnal inversion interface (an example on Figure 2). Based on GCM model efforts, looks like the low-level jet is a large scale circulation feature. The westward wind at 2 km altitude shown on Figure 2 is also show up nicely in the MCD. The jet could be forced by the diurnal cycle. The dustier atmosphere, when arrival of northern autumn equinox, also contributes to decrease the nighttime Richardson number by two means: strengthening of the nighttime low-level jet deeping the near-surface wind shear and weakening near-surface atmospheric stability by increasing the nighttime surface temperature and decreasing of atmospheric temperature. A third possible strengthening of the nighttime turbulence at Jezero could be the convergence, after 01:00 LTST, of downslope winds blowing from NW rim fighting against SE winds blowing both from east crater rims and from Jezero mons (located SE outside the crater), producing a big whirlpool inside the crater (Figure 4) that could be the responsible of the high variability of wind directions observed by MEDA. 4. Nightime turbulence observed with MEDA The rapid fluctuations of pressure (moreover during high dust periods), TKE (derived only with horizontal wind speeds, that will be updated with vertical winds in the future) and wind speeds observed during nighttime with MEDA (Figures 5 and 6) is a clear indication of nocturnal turbulence. 5. Figures Figure 1: TKE diurnal cycle predicted with MRAMS for Jezero crater at Ls0, 60, 90, 105, 160, 180 and 270. Figure 2: MRAMS vertical cross-section (Jezero’s west rim to east rim) at 21:35 LTST of Ls=180º -corresponding to Mars 2020 sol #362- of total wind (zonal + meridional) in colored shadowed, zonal + vertical (exaggerated x5) wind in white arrows and TKE in black contours. The west crater rim is the hill on the left. Perseverance rover is located at x ≈ 17 km. Figure 3: MRAMS vertical profiles of wind magnitude, wind shear, Richardson number (Ri) and TKE for Ls180 at Mars 2020 location corresponding to Mars 2020 sol #362 (Ls=180º). Once the critical Richardson Number is reached (Ri ∼< 0.25, red line). Figure 4: Near-surface winds (vectors) and potential temperature (shaded) as predicted on numerical grid 5. Vectors are plotted at every other grid point. Topography contours are shown in black. Wind vector scale is shown in the bottom right area of the panels. hh:mm LTST on the top right. A big whirlpool inside the crater could be responsible for the large variability of wind directions observed by MEDA after 01:00 LTST. Figure 5: MEDA TKE (derived only with horizontal wind speeds, that will be updated with vertical winds in the future), wind direction and horizontal wind speed instantaneous measurements for the period 00:14 to 00:23 LTST at sol #73. Figure 6: Diurnal cycle of MEDA TKE averaged over 5 min for sols #73-87. 6. References [1] Rodriguez-Manfredi et al. 2020; [2] Pla-Garcia et al. 2021; [3] Mellor and Yamada 1974; [4] Davis 2000; [5] Blackadar 1957; [6] Thorpe and Guymer 1977; [7] Mahrt 1981; [8] Miles 1961; [9] Banfield et al. 2020; [10] Chatain et al. 2021

Since 2010 several amateur astronomers have discovered flashes of light that result from the collision of objects of 5-20 m in diameter, impacting in Jupiter’s atmosphere at velocities higher than 60 km/s. These objects release energies of the order of 1015-1016 J, or 200-1000 kiloton [1] and become observable even with small-size telescopes. Up to 2019, 6 such impact flashes have been observed by amateur astronomers [2-3]. In one case, the quality of the light-curve allowed to investigate the physical composition of the impacting object through the effect of its density when comparing with models of impacts and with the likely conclusion of a stony composition [4]. An important step forward has been the availability of software tools that allow to check video files of Jupiter to automatically search for the faint trace of an impact. The software DeTeCt is a free-software designed for the task [5] and available at: http://www.astrosurf.com/planetessaf/doc/project_detect.php Here we report the characteristics of 3 additional impacts detected in 2020-2021. These were a very bright flash discovered on 13 September, which was simultaneously observed by at least 9 observers from Brazil to Germany. A new impact was discovered by Kothji Arimatsu from Kyoto University on 15 October 2021, running a dedicated telescope with two CMOS cameras, and also observed by amateur astronomers in Japan and Singapore. After finding this impact, one of these observers used the DeTeCt software on past observations acquired one year earlier on 11 Aug. 2020 finding an additional impact that had passed unnoticed. These 3 impacts in 2020 and 2021 were observed by a variety of cameras with different sensitivities to color. This allows a good quantification of the effective brightness temperature of the impact and a more accurate measurement of the energy released, and thus, a better estimation of the mass of the impactor. The event observed on 13 September 2021 was the brightest flash observed in Jupiter. The 15 October 2021 event was also brighter than most previous flashes and it impacted Jupiter in an area observed by the Junocam instrument 28 hours later. However, Junocam did not observe a remnant even at a spatial resolution over the impact area of ~30 km/pix. We present light-curves of these three impacts and their brightness temperatures from multi-wavelength observations. Brightness temperatures compare well with the spectra of a smaller impact observed in 2018 by the Juno mission [8]. From the light-curves and brightness temperatures we deduce masses, sizes and how these 3 new objects, and the combined data of the DeTeCt project set ups new constrains in the current impact rate in the Jupiter System [3, 7]. We also evaluate the quality of the structures observed in the simultaneous lightcurves and their capability to constrain models of bolides impacting Jupiter’s atmosphere [2,4]. Figure: Composite images of the three impacts discussed in this work together with multi-wavelength lightcurves of the central impact from one of the colour videos obtained. The rate between blue and red is indicative of a high brightness temperature. Acknowledgments We are very grateful to all the observers of these impacts supplying the observations and reports used in this analysis. These are: (1) Victor PS Ang (Singapore), who observed the 2020-08-11 impact and was one of the 3 amateur observers of the 2021-11-15 impact. (2) Jose Luis Pereira (Brazil), Harald Paleske (Germany), Jean-Paul Arnould (France), Didier Walliang (France), Michel Jacquesson (France), Cosmin Sabdu Val (Romania), Jean-Christophe Griveau (France), who all observed and recorded videos of the 2020-09-13 impact together with additional colleagues operating their telescopes. In addition Maciej Libert (Germany), Simone Galelli (Italy) both reported visual observations of the impact looking at the eyepiece of their telescopes. (3) “Yotsu” (Japan) and Yasunobu Higa (Japan) who were two of the observers of the 2021-11-15 impact. We are also grateful to Kothji Arimatsu and the PONCOTS team from Kyoto Observatory for comments on the October 2021 impact they originally discovered and announced making possible its detection in amateur videos acquired from Singapore and Japan. In addition, we are extremely grateful to the many amateur astronomers taking part in the DeTeCt project and committing a large amount of their time to look for impacts. References [1] Hueso, R., Wesley A. et al. (2010). First Earth-based detection of a superbolide on Jupiter, The Astrophysical Journal Letters (721), 2010. [2] Hueso, R. et al. (2013). Impact flux on Jupiter: From superbolides to large-scale collisions. Astronomy & Astrophysics, 560, A55. [3] Hueso, R., Delcroix, M. et al. (2018). Small impacts on the giant planet Jupiter, Astronomy & Astrophysics, A68. [4] Sankar, R. et al. (2020). Fragmentation modelling of the August 2019 impact on Jupiter, Montly Notices of the Royal Astronomical Society, 493, 4622-4630. [5] Hueso, R. Et al. (2018). Detectability of possible space weather effects on Mars upper atmosphere and meteor impacts in Jupiter and Saturn with small telescopes. Journal of Space Weather and Space Climate, 8, A57. [6] Delcroix, M. et al. (2019). Jupiter impact detection project, Europlanet Science Conference, EPSC2019-970. [7] Delcroix, M. et al. (2020). Impact detection on Jupiter through amateur’s processing of their own videos using DeTeCt, Europlanet Science Conference, EPSC2020-775. [8] Giles, R. S. et al. (2021). Detection of a Bolide in Jupiter’s atmosphere with Juno UVS, Geophysical Research Letters, 48, e2020GL091797.

The Visual Monitoring Camera (VMC) on Mars Express (MEX) has the capability to capture full disk images of Mars from apocenters. This has allowed us to compile a large archive of images showing Mars at different local times, including the twilight region beyond the day side terminator. The observation of clouds in twilight enables the estimation of their “minimum altitude”, as they must be high enough over the surface to be illuminated by the sun and appear as bright patches over the darkness of the night. A systematic study of clouds seen in twilight was made by Hernández-Bernal et al. (2021b). This work extends the analysis, increasing the dataset and focusing on dynamics. VMC has the rare capability to obtain videos showing atmospheric dynamics (e.g. supporting material in Hernández-Bernal et al., 2021a) and we exploit this capability to estimate the accurate altitude of clouds, perform cloud tracking, and analyze their cloud dynamics. Figure 1. Reproduced from Hernández-Bernal et al. (2021b). (a) Scheme of observation of clouds in twilight. (b-e) examples of clouds in twilight observed by VMC. See original paper for full description. We run the automated cloud detector pipeline developed by Hernández-Bernal et al. (2021b), to include most recent observations into our dataset. Most recent observations in MY36 reproduce previously reported patterns in the distribution of mesospheric clouds in twilight (Figure 2), and the extended coverage hints the presence of more clouds in twilight than previously observed, at the starting of the year in the southern mid-latitudes, and in the northern mid-latitudes at the starting of the local autumn. Figure 2. Recent observations of clouds in twilight found by VMC in MY36. The horizontal axis represents the Solar Longitude (Ls). See the equivalent graph for the whole dataset in Hernández-Bernal et al. (2021b) We use this extended dataset of clouds in twilight observed by VMC to feed a newly developed pipeline that creates videos showing the dynamics of such clouds. This new pipeline outputs around 500 videos. All these videos are manually analyzed and cloud tracking is performed when possible. Less than 100 videos exhibit a good quality and show clouds that are suitable for cloud tracking. We compare our cloud tracking to expected winds as given by the Mars Climate Database (MCD; Millour et al., 2015). The results of this work are expected to be a valuable dataset, as it involves the direct measurement of winds at specific altitudes, very often in the mesosphere of Mars. Määttänen et al. (2010) also measured winds on Martian mesospheric clouds based on the stereo capabilities of HRSC (High Resolution Stereo Camera) onboard Mars Express. Figure 3. An example of clouds seen in twilight by VMC. This is a projected image that is part of a long observation from which a video was made. White curves indicate the terminator, and the limit where clouds below 50km cannot receive the illumination of the sun and therefore will not be visible. The accurate altitude of clouds can be estimated from videos showing clouds appearing in the night side of the terminator. An animated version of this image can be found in https://figshare.com/articles/media/Twilight_video_example/19772797 References Hernández‐Bernal, J., Sánchez‐Lavega, A., del Río‐Gaztelurrutia, T., Ravanis, E., Cardesín‐Moinelo, A., Connour, K., ... & Hauber, E. (2021). An Extremely Elongated Cloud over Arsia Mons Volcano on Mars: I. Life Cycle. Journal of Geophysical Research: Planets, 126(3), e2020JE006517. Hernández‐Bernal, J., Sánchez‐Lavega, A., del Río‐Gaztelurrutia, T., Hueso, R., Ravanis, E., Cardesín‐Moinelo, A., ... & Titov, D. (2021). A Long‐Term Study of Mars Mesospheric Clouds Seen at Twilight Based on Mars Express VMC Images. Geophysical Research Letters, 48(7), e2020GL092188. Määttänen, A., Montmessin, F., Gondet, B., Scholten, F., Hoffmann, H., González-Galindo, F., ... & Bertaux, J. L. (2010). Mapping the mesospheric CO2 clouds on Mars: MEx/OMEGA and MEx/HRSC observations and challenges for atmospheric models. Icarus, 209(2), 452-469. Millour, E., Forget, F., Spiga, A., Navarro, T., Madeleine, J. B., Montabone, L., & Lopez-Valverde, M. A. (2015, September). The Mars climate database (MCD version 5.2). In European Planetary Science Congress (Vol. 10).

On May 31, 2020 a short-lived convective storm appeared in one of the small cyclones of Jupiter's South Temperate Belt (STB) at planetographic latitude 30.8S. The outbreak was captured by amateur astronomer Clyde Foster in methane-band images, became widely known as Clyde's Spot, and was imaged at very high resolution by the Junocam instrument on board the Juno mission 2.5 days later. Junocam images showed a white two-lobed cyclonic system with high clouds observed in the methane-band at 890 nm. The storm evolved over a few days to become a dark feature that showed turbulence for months, presented oscillations in its drift rate, and slowly expanded, first into a Folded Filamentary Region (FFR), and later into a turbulent segment of the STB over a timescale of one year. On August 7, 2021, a new storm strikingly similar to Clyde's Spot erupted in a cyclone of the STB. The new storm exhibited first a similar transformation into a turbulent dark feature, and later transformed into a dark cyclone fully formed by January 2022. We compare the evolution into a FFR of Clyde's Spot with the formation of a FFR observed by Voyager 2 in 1979 in the South South Temperate Belt (SSTB) after a convective outburst in a cyclone that also developed a two-lobed shape. We also discuss the contemporaneous evolution of an additional cyclone of the STB, which was similar to the one were Clyde's Spot developed. This cyclone did not exhibit visible internal convective activity, and transformed from pale white in 2019, with low contrast with the environment, to dark red in 2020, and thus, was very similar to the outcome of the second storm. This cyclone became bright again in 2021 after interacting with Oval BA. We present observations of these phenomena obtained by amateur astronomers, ground-based telescopes, Hubble Space Telescope and Junocam. This study reveals that short-lived small storms that are active for only a few days can produce complex longterm changes that extend over much larger areas than those initially covered by the storms. In a second paper [In tilde urrigarro et al., 2022] we use the EPIC numerical model to simulate these storms and study moist convection in closed cyclones. We are very thankful to the large community of amateur observers operating small telescopes that submit their Jupiter observations to databases such as PVOL and ALPO-Japan. We are also grateful to two anonymous reviewers for their comments that improved the clarity of this paper. This work has been supported by Grant PID2019-109467GB-I00 funded by MCIN/AEI/10.13039/501100011033/and by Grupos Gobierno Vasco IT1366-19. PI acknowledges a PhD scholarship from Gobierno Vasco. GSO and TM were supported by NASA with funds distributed to the Jet Propulsion Laboratory, California Institute of Technology under contract 80NM0018D0004. C. J. Hansen was sup-ported by funds from NASA, USA to the Juno mission via the Planetary Science Institute. IOE was supported by a contract funded by Europlanet 2024 RI to navigate Junocam images, now available as maps in PVOL at http://pvol2.ehu.eus. Europlanet 2024 RI has received funding from the European Unions Horizon 2020 research and innovation programme under grant agreement No 871149. G.S. Orton, S. R. Brueshaber, T. W. Momary, K. H. Baines and E. K. Dahl were visiting Astronomers at the Infrared Telescope Facility, which is operated by the University of Hawaii under contract 80HQTR19D0030 with the National Aeronautics and Space Administration. In addition, support from NASA Juno Participating Scientist award 80NSSC19K1265 was provided to M.H. Wong. This work has used data acquired from the NASA/ESA Hubble Space Telescope (HST) , which is operated by the Association of 807 Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These HST observations are associated with several HST observing programs: GO/DD 14661 (PI: M.H. Wong) , GO/DD 15665 (PI: I. de Pater) , GO/DD 15159 (PI: M. H. Wong) , GO/DD 15502 (PI: A. Simon) , GO/DD 14661 (PI: M. H. Wong) , GO/DD 16074 (PI: M.H. Wong) , GO/DD 16053 (PI: I. de Pater) , GO/DD 15929 (PI: A. Simon) , GO/DD 16269 (PI: A. Simon) . PlanetCam observations were collected at the Centro Astronomico Hispanico en Andalucia (CAHA) , operated jointly by the Instituto de Astrofisica de Andalucia (CSIC) and the Andalusian Universities (Junta de Andalucia) . This work was enabled by the location of the IRTF and Gemini North telescopes within the Mauakea Science Reserve, adjacent to the summit of Maunakea. We are grateful for the privilege of observing Kaawela (Jupiter) from a place that is unique in both its astronomical quality and its cultural signifi-cance. This research has made use of the USGS Integrated Software for Imagers and Spectrometers (ISIS) . Voyager 2 images were accessed through The PDS Ring-Moon Systems Nodes OPUS search service.

Dark spots on Neptune observed by Voyager and the Hubble Space Telescope are thought to be anticyclones with lifetimes of a few years, in contrast with very long-lived anticyclones in Jupiter and Saturn. The full life cycle of any Neptune dark spot has not been captured due to limited temporal coverage, but our Hubble observations of a recent feature, NDS-2018, provide the most complete long-term observational history of any dark vortex on Neptune. Past observations suggest some dark spots meet their demise by fading and dissipating without migrating meridionally. On the other hand, simulations predict a second pathway with equatorward migration and disruption. Our HST observations suggest NDS-2018 is following the second pathway. Some of the HST observations reveal transient dark features with widths of about 4000 to 9000 km, at latitudes between NDS-2018 and the equator. The secondary dark features appeared before changes in the meridional migration of NDS-2018 were seen. These features have somewhat smaller size and much smaller contrast compared to the main dark spot. Discrete secondary dark features of this scale have never been seen near previous dark spots, but global-scale dark bands are associated with several previous dark spots in addition to NDS-2018. The absolute photometric contrast of NDS-2018 (as large as 19%) is greater than previous dark spots, including the Great Dark Spot seen by Voyager. New simulations suggest that vortex internal circulation is weak relative to the background vorticity, presenting a clearly different case from stronger anticyclones observed on Jupiter and Saturn.

A recent work (Hernández-Bernal et al., 2021) described the Arsia Mons Elongated Cloud (AMEC), an impressive orographically generated cloud that appears next to the Arsia Mons volcano on Mars during the early morning on a daily basis in southern spring and summer. The most visually striking characteristic of this cloud is its extremely elongated shape.This spectacular cloud is formed by underlying dynamical and microphysical processes that remain to be elucidated. To that end, we run the LMD (Laboratoire de Météorologie Dynamique) MMM (Mars Mesoscale Model; Spiga and Forget, 2009) for Solar Longitude 270º, with a grid resolution of 10km. The model shows that the interaction of fast transient easterly winds with the summit of Arsia Mons results in strong ascending winds on the western slope of the volcano, seasonally and diurnally coincident with the occurrence of the AMEC according to observations. These ascending winds propagate vertically and result in a temperature drop which takes values of down to -30K in the hygropause (around 45 km over the areoid). This results in extreme relative humidity values and condensation, spatially coincident with what Hernández-Bernal et al. (2021) called the head of the AMEC. We expect advection by easterly winds to produce the particular elongated shape of the AMEC, however the advection of condensed particles is not clearly reproduced by the model.This AMEC study demonstrates that coupling the analysis of mesoscale modeling with imagery monitoring on elongated clouds help to better understand the involved processes to form the cloud. We aim to search for similar mechanisms in other visually resemblant clouds, like those reported by Clancy et al. (2006; 2021), and others observed by the Visual Monitoring Camera onboard Mars Express, among other imagers. In the meantime, the AMEC is expected to appear again in early June 2022 and different instruments are already planning observations.References:Hernández‐Bernal, Jorge, et al. "An extremely elongated cloud over Arsia Mons volcano on Mars: I. Life cycle." Journal of Geophysical Research: Planets 126.3 (2021): e2020JE006517. Spiga, Aymeric, and François Forget. "A new model to simulate the Martian mesoscale and microscale atmospheric circulation: Validation and first results." Journal of Geophysical Research: Planets 114.E2 (2009). Clancy, R. Todd, et al. "Valles Marineris cloud trails." Journal of Geophysical Research: Planets 114.E11 (2009). Clancy, R. Todd, et al. "Mars perihelion cloud trails as revealed by MARCI: Mesoscale topographically focused updrafts and gravity wave forcing of high altitude clouds." Icarus 362 (2021): 114411.

Jupiter's Great Red Spot (GRS) is a remarkable phenomenon among solar system atmospheres. In addition to its unique dynamical properties, the vertical structure of its clouds and hazes is a relevant subject of study, being of particular interest the unknown chromophore species responsible for the GRS characteristic reddish color. In a recently published paper (Anguiano-Arteaga et al., 2021) we showed the existence of a stratospheric haze (P < 100 mbar) that seemed to be compatible with the chromophore-candidate proposed by Carlson et al. (2016), although a second coloring agent located in the upper tropospheric levels (P < 500 mbar) was also suggested.In this study, we have analyzed high-resolution images obtained with the Hubble Space Telescope’s Wide Field Camera 3 between 2015 and 2021, with a spectral coverage from the UV to the near IR, including two methane absorption bands. Following the same procedure as in our previous paper, we have obtained the spectral reflectivity of the GRS and a few dynamically interesting regions in the surrounding area under different viewing geometries.From the measured spectra, and following the scheme proposed by Anguiano-Arteaga et al. (2021), we retrieved several key atmospheric parameters (optical depths, particle vertical and size distributions and refractive indices) for each of the regions using the NEMESIS radiative transfer suite (Irwin et al., 2008). We show the spatial and temporal variations on these parameters, including the evolution of the properties of the chromophore species.References- Anguiano-Arteaga, A., Pérez-Hoyos, S., Sánchez-Lavega, A., Sanz-Requena, J. F., & Irwin, P. G. J. (2021). Vertical distribution of aerosols and hazes over Jupiter's Great Red Spot and its surroundings in 2016 from HST/WFC3 imaging. J. Geophys. Res. Planets., 126, e2021JE006996 https://doi.org/10.1029/2021JE006996- Carlson, R.W., Baines, K.H., Anderson, M.S., Filacchione, G., & Simon, A.A. (2016). Chromophores from photolyzed ammonia reacting with acetylene: Application to Jupiter’s Great Red Spot. Icarus, 274, 106-115. https://doi.org/10.1016/j.icarus.2016.03.008- Irwin, P.G.J., Teanby, N.A., de Kok, R., Fletcher, L.N., Howett, C.J.A., Tsang, C.C.C., Wilson, C.F., Calcutt, S.B., Nixon, C.A., & Parrish, P. D. (2008). The NEMESIS planetary atmosphere radiative transfer and retrieval tool. J. of Quant. Spec. and Radiative Transfer, 109 , 1136-1150. https://doi.org/10.1016/j.jqsrt.2007.11.006

The Planetary Virtual Observatory & Laboratory database (PVOL, http://pvol2.ehu.eus/pvol2/) contains a large set of amateur observations of solar system planets and is a tool that has been widely used in pro-am collaborations. PVOL is integrated in the Virtual European Solar and Planetary Access (VESPA, http://vespa.obspm.fr/planetary/data/) set of services developed through Europlanet 2020 RI and Europlanet 2024 RI, further increasing its visibility in the professional astronomy landscape. The essential content of PVOL is images of the planets obtained by amateur astronomers. This content is continuously updated by registered users, and a web manager who uploads submissions from not registered users sent by email to pvol@ehu.eus. Close to planetary oppositions, daily observations of Mars, Jupiter and Saturn allow detailed surveys of their atmospheric activity. Near maximum elongation of Venus, amateur images unveil large-scale structures in the clouds. Amateur observations of Uranus and Neptune are not so common, but amateurs obtain very valuable observations of these atmospheres in special cases when alerts of new large atmospheric features are sent. The potential for science of these data sets is very large, and PVOL contains a list of >40 scientific publications led by researchers from several independent teams using data from PVOL in different domains. Further observations of Galilean moons and even our Moon can be submitted to PVOL where the data can serve different purposes, including educational ones. Thus, PVOL is increasing is role as a general service to the planetary sciences community and the amateur astronomers collaborating with different research groups. Figure 1 shows a set of various images of planets available in the database. Figure1: Set of amateur images in the PVOL database obtained by different observers and covering different scientific domains. In recent years, new data types have been added including: (i) Maps of Junocam images of Jupiter (see Figure 2), (ii) photometry and spectroscopic data. The system also keeps track of publications using PVOL data and supports specific campaigns, like the Venus BepiColombo flyby, or the search for Jovian Impacts in collaboration with the DeTeCt project at http://www.astrosurf.com/planetessaf/doc/project_detect.php. In addition, PVOL contains an alert section where observational alerts are updated regularly besides submissions by email to specific e-mail lists of amateur astronomers. In this contribution we review the status of the data in PVOL (see Figure 3) and additional services and we indicate future plans for PVOL including a better handling of photometric and spectroscopic data submitted by amateur astronomers. Figure 2: One of the many Junocam maps of Jupiter in the PVOL database. Figure 3: Number of observations per target currently stored in PVOL. Jupiter numbers include maps of Jupiter obtained by the Junocam instrument on the Juno mission. Acknowledgements We are very grateful to the large community of amateur astronomers submitting their observations to PVOL. We are also grateful to C. Hansen and G. S. Orton for their generous collaboration in helping us with data from the Junocam instrument, and also from their continuous support of pro-am activities around Juno. Europlanet 2024 RI has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 871149.

In this work, we have analyzed images provided by the Hubble Space Telescope's Wide Field Camera 3 (HST/WFC3) in December 2016, with a spectral coverage from the ultraviolet to the near infrared. We have obtained the spectral reflectivity of the GRS and its surroundings, with particular emphasis on selected, dynamically interesting regions. A spectral characterization of the GRS area is performed following two different procedures: (a) in terms of Altitude/Opacity and Color Indices (AOI and CI); (b) by means of automatic spectral classification. We used the NEMESIS radiative transfer suite to retrieve the main atmospheric parameters (e.g., particle vertical and size distributions, refractive indices) that are able to explain the observed spectral reflectivity. The optimal a priori model atmosphere used for the retrievals is obtained from a grid of about 12,000 different atmospheric models, and choosing the one that best fits South Tropical Zone (STrZ) spectra and its observed limb-darkening. We conclude that the spectral reflectivity of the GRS area is well reproduced with the following layout: (a) a stratospheric haze with its base near the 100 mbar level, with optical depths at 900 nm of the order of unity and particles with a size of 0.3 μm; (b) a more vertically extended tropospheric haze, with τ (900 nm) ∼10 down to 500 mbar and micron sized particles. Both haze layers show a stronger short wavelength absorption, and thus both act as chromophores. The altitude difference between clouds tops in the GRS and surrounding areas is ∼10 km.

We use in situ environmental measurements by the Mars Science Laboratory (MSL) mission to obtain the surface energy budget (SEB) across Curiosity's traverse during the first 2500 sols of the mission. This includes values of the downwelling shortwave solar radiation, the upwelling solar radiation reflected by the surface, the downwelling longwave radiation from the atmosphere, the upwelling longwave radiation emitted by the surface, the sensible heat flux associated with turbulent motions, and the latent heat flux associated with water phase changes. We then analyze their temporal variation on different timescales and relate this to the mechanisms causing these variations. Through its Rover Environmental Monitoring Station, MSL allows for a more accurate determination of the SEB than its predecessors on Mars. Moreover, the unprecedented duration, cadence, and frequency of MSL environmental observations allow for analyses of the SEB from diurnal to interannual timescales. The results presented in this article can be used to evaluate the consistency with predictions from atmospheric numerical models, to validate aerosol radiative properties under a range of dust conditions, to understand the energy available for solar-powered missions, and to enable comparisons with measurements of the SEB by the Perseverance rover at Jezero crater.

Remote sensing observations suffer significant limitations when used to study the bulk atmospheric composition of the giant planets of our solar system. This impacts our knowledge of the formation of these planets and the physics of their atmospheres. A remarkable example of the superiority of in situ probe measurements was illustrated by the exploration of Jupiter, where key measurements such as the determination of the noble gases' abundances and the precise measurement of the helium mixing ratio were only made available through in situ measurements by the Galileo probe. Here we describe the main scientific goals to be addressed by the future in situ exploration of Saturn, Uranus, and Neptune, placing the Galileo probe exploration of Jupiter in a broader context. An atmospheric entry probe targeting the 10-bar level would yield insight into two broad themes: i) the formation history of the giant planets and that of the Solar System, and ii) the processes at play in planetary atmospheres. The probe would descend under parachute to measure composition, structure, and dynamics, with data returned to Earth using a Carrier Relay Spacecraft as a relay station. An atmospheric probe could represent a significant ESA contribution to a future NASA New Frontiers or flagship mission to be launched toward Saturn, Uranus, and/or Neptune., 27 pages, 9 figures, White Paper submitted in response to ESA's Call for Voyage 2050 Science Themes. arXiv admin note: substantial text overlap with arXiv:1708.00235

In a recently published paper, we reported the existence and properties of the Arsia Mons Elongated Cloud (AMEC; Hernández-Bernal et al., 2021). We are now exploring models for the theoretical understanding of this outstanding phenomenon. The AMEC forms at sunrise over the western slope of the Arsia Mons volcano, and for ~3 hours expands to the west following zonal winds, leaving behind a characteristic white bright tail. This process repeats in a daily cycle for a long season around the southern solstice. According to observations in MY34, the AMEC reaches a length of up to 1800 km, and expands at a velocity of around 170 m/s (~130 m/s in other years) at ~45 km in altitude. In comparison, winds predicted by the Global Circulation Model LMD-MCD are ~60m/s (Millour et al. 2018). The cloud is clearly driven by upward winds forced by the topography of the volcano. We are analysing from the theoretical perspective the formation and particular features of this cloud. References Hernández‐Bernal, J., Sánchez‐Lavega, A., del Río‐Gaztelurrutia, T., Ravanis, E., Cardesín‐Moinelo, A., Connour, K., ... & Hauber, E. (2021). An extremely elongated cloud over Arsia Mons volcano on Mars: I. Life cycle. Journal of Geophysical Research: Planets, 126(3), e2020JE006517. Millour, E., F. Forget,A. Spiga, et al. "Mars climate database. (Version 5.3)" From Mars Express to ExoMars (2018)

Amateur astronomy of the Solar System is living a golden age with major contributions to modern planetary science. These contributions cover a wide spectrum of topics that range from the discovery of impacts in Jupiter [1-2], to the observation of stellar occultations by minor bodies [3-4], the characterization of unexpected high-atmospheric events in Mars [5], or the characterization of giant storms on Jupiter [6] and Saturn [7-8]. Besides these examples of high-profile publications, there is an increasing number of amateur contributions to dozens of studies of planetary atmospheres and countless contributions to the study of minor bodies. While we focus here in the role of amateur astronomy observations of planetary atmospheres, we also recognize the varied and healthy professional and amateur collaborations in other areas of solar system astronomy. The reasons behind this golden age lie in the two sides of the collaboration: On the side of amateur astronomers, many of them use very efficient detectors and advanced software tools, and they are highly connected at an international level. Thus, they provide high-quality observations on a regular basis to professional astronomers, or have strong analysis teams like the JUPOS team as an example (http://jupos.privat.t-online.de/index.htm). These frequent amateur observations provide essential monitoring of the temporal evolution of planetary atmospheres. On the other side, professional astronomers are aware of the potential of these observations and actively seek the collaboration of amateur astronomers and citizen scientists. A key case in this regard is NASA’s Juno mission to the giant planet Jupiter, and its large-scale collaboration around the JunoCam instrument on the mission Juno website: https://www.missionjuno.swri.edu/. The mission has been recently extended until 2025 and details of the contribution of amateur observers to this new mission scenario are presented by Orton et al. in session ODAA5 in this meeting. Other examples of professionals seeking a global collaboration with amateurs are the various professional and amateur astronomy services and workshops organized by research projects like the Europlanet 2020 Research Infrastructure (2016-2019) and Europlanet 2024 Research Infrastructure (2020-2024). We anticipate that the trend of amateur astronomy playing an important role in providing additional data sets to space missions will continue to grow and we advocate for the early establishment of such collaborations. We review some of the elements that have made the collaboration of amateur astronomers with the Juno mission so fruitful for both parties and how this collaboration has grown beyond Jupiter into enhanced collaborations in other fields through networking amateur astronomers and providing a successful example to other fields. We also discuss future ground-based high-resolution amateur observations of Solar System planets in support of future missions. These include the James Webb Space Telescope observations of planets (launch in October 2021), ESA’s Jupiter Icy moons Explorer (JUICE, launching in 2022) and NASA’s Europa Clipper missions to the Jupiter system in the early 2030s, the in situ exploration of Saturn’s moon Titan by the Dragonfly mission (NASA) in 2034, the Envision mission to Venus (if selected by ESA), and possible future missions to the Icy Giants Uranus and Neptune. Each of these ambitious missions will benefit from the strong partnership between amateur and professional planetary scientists. The first in this line is the JWST observations of Giant planets to be conducted in 2022 (see Fletcher et al. in session OPS3 in this conference). Finally, we also show some professional and amateur networking elements developed under the umbrella of the Europlanet projects, including the recently launched Europlanet Telescope Network (https://bit.ly/2Br5LDt), and we present possible scenarios for future pro-am collaborations beyond the end of the Europlanet 2024 project. Acknowledgements Part of this research has been supported by Europlanet 2024 RI. Europlanet 2024 RI has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 871149. References [1] Sánchez-Lavega et al. The impact of a large object on Jupiter in 2009 July, ApJL, 715, 2, L150 (2010) [2] Hueso et al. First Earth-based detection of a superbolide in Jupiter, ApJL, 721, 2, L129 (2010). [3] Ortiz et al. The size, shape, density and ring of the dwarf planet Haumea from a stellar occultation, Nature, 520, 219-223 (2017) [4] Marques-Oliveira et al. Structure and evolution of Triton’s atmosphere from the October 2017 stellar occultation, A&A (submitted). [5] Sánchez-Lavega et al. An extremely high-altitude plume seen at Mars’ morning terminator, Nature, 518, 525-528 (2015). [6] Sánchez-Lavega et al. Depth of a strong jovian jet from a planetary-scale disturbance driven by storms, Nature, 451, 437-440 (2008). [7] Fletcher et al. Thermal Structure and Dynamics of Saturn’s Northern Springtime Disturbance, Science, 332, 1413 (2011). [8] Sánchez-Lavega et al. Deep winds beneath Saturn’s upper clouds from a seasonal long-lived planetary-scale storm, Nature 475, 71-74 (2011).

Meteors and fireballs, often as part of meteor showers, are commonly observed in the atmosphere of Earth. The same phenomena is expected to take place in other planets (Christou, 2005). Observations are rare, as no suitable instruments have been launched in interplanetary missions, however, these observations can push forward our understanding of interplanetary dust (Christou et al., 2019). In recent years, a number of impacts on Jupiter have been reported based on ground based amateur observations (Hueso et al., 2018) and Juno observations (Giles et al., 2021). On Mars, the Panoramic Camera on Mars Exploration Rover Spirit tried to observe meteors, with no conclusive detections (Domokos et al., 2007), however a meteor was possibly imaged by a navigation camera (Selsis et al., 2005). The Visual Monitoring Camera (VMC) onboard Mars Express is a wide field camera initially designed as an engineering camera (Ormston et al., 2011). VMC was recently upgraded to a science instrument, and in recent years different works have shown the scientific capabilities of this camera (e.g. Sánchez-Lavega 2018; Hernández-Bernal et al., 2021a;2021b). As part of the VMC science program, we performed a few campaigns to try to find meteors or fireballs. To maximize probabilities, we programmed observations coincident with theoretically predicted meteor showers on Mars. While the sensibility of the VMC sensor is low, which reduces the probability to find meteors, its field of view is very wide compared to other instruments, which enhances the probabilities. So far, we have not captured any clear meteor or fireball. Methodology We planned our campaigns based on predictions published by Christou (2010). Hardware limitations require all other instruments to be switched off when VMC is observing, this is an important limitation to this work, as only a few observations could be performed, and VMC observations cannot be very long. VMC accepts exposures of up to ~90 s, however observations longer than ~30 s are highly affected by the thermal noise of the sensor, additionally there is a gap of around 48 s between VMC images. As a result, less than 40% of the time VMC is switched on can be effectively used for monitoring. Exposures of a few seconds by VMC are usually noisy, and they require processing to extract the presence of dim objects, such as stars, planets (e.g. https://twitter.com/esaoperations/status/1247096203550101504), or in this case, meteors. In the case of meteors, we expect them to appear as dim lines in only one image, then the best way to extract the noise from an image is by making a synthetic dark from images obtained close in time. Considering the sensibility of VMC as revealed by observations of stars, we expect it to be able to capture only very bright meteors, around absolute magnitudes of -6 to -10. Figure 1 shows an example of the simulations performed to analyze observability. Figure 1. Results We performed two campaigns to try to find meteors or fireballs, table 1 summarizes these campaigns. Parent Comet Ls Velocity SZA Observations Accumulated time 5335 Damocles 47.8 29.9 km/s 98.4º 2019-07-03_23.54-01.13 25 minutes 1P Halley 325.9 53.8 km/s 121.4º 2020-12-04_01.35-02.04 2020-12-15_02.53-03.21 2020-12-20_01.42-02.05 21 minutes Table 1. Meteor shower details from Table 2 in Christou (2010). Once processed, images did not show any significant trace potentially related to a meteor burning in the atmosphere. The total effective observation time was 46 minutes, part of this time elapsed out of the expected area for the meteor shower. Figure 2. Scheme of an observation. The area expected for the meteor shower is green shaded. Dark shaded area is the night. Conclusions We did not achieve positive results. The main reason is probably the low sensibility of the VMC sensor. While VMC is a low quality engineering camera designed in the 90s, modern commercial cameras can achieve very high sensibilities. The technical planning of these campaigns shows that VMC-like cameras could be a tool suitable to monitor meteor activity on Mars and other planets from space in the future, as already pointed by Christou et al. (2012). The wide field of view of VMC, when exploited from a moderate distance to the planet, provides full-disk images covering wide areas, and thus potentially enabling the large-scale monitoring of meteor activity. References Christou, A. A., "Predicting Martian and Venusian meteor shower activity." Modern Meteor Science An Interdisciplinary View. Springer, Dordrecht, 2005. 425-431. Christou, A. A., "Annual meteor showers at Venus and Mars: lessons from the Earth." Monthly Notices of the Royal Astronomical Society 402 (2010): 2759-2770. Christou, A. A., et al. "Orbital observations of meteors in the Martian atmosphere using the SPOSH camera." Planetary and Space Science 60 (2012): 229-235. Christou, A. A., et al. "Extra-terrestrial meteors." (2020). Chapter 5 in “Meteoroids: Sources of Meteors on Earth and Beyond”, Cambridge University Press (2019) Domokos, Andrea, et al. "Measurement of the meteoroid flux at Mars." Icarus 191 (2007): 141-150. Hernández‐Bernal, J., et al. "An extremely elongated cloud over Arsia Mons volcano on Mars: I. Life cycle." Journal of Geophysical Research: Planets 126 (2021a): e2020JE006517. Hernández‐Bernal, J., et al. "A Long‐Term Study of Mars Mesospheric Clouds Seen at Twilight Based on Mars Express VMC Images." Geophysical Research Letters 48 (2021b): e2020GL092188. Giles et al. “Detection of a bolide in Jupiter’s atmosphere with Juno UVS”. Geophysical Research Letters, 48 (2021). Hueso, Ricardo, et al. "Small impacts on the giant planet Jupiter." Astronomy & Astrophysics 617 (2018): A68. Ormston, T., et al. "An ordinary camera in an extraordinary location: Outreach with the Mars Webcam." Acta Astronautica 69.7-8 (2011): 703-713. Sánchez-Lavega, A., et al. "Limb clouds and dust on Mars from images obtained by the Visual Monitoring Camera (VMC) onboard Mars Express." Icarus 299 (2018): 194-205. Selsis, Franck, et al. "A martian meteor and its parent comet." Nature 435.7042 (2005): 581-581.

Jupiter’s atmosphere holds a large variety of vortices. In the transition region between the North Equatorial Band (NEBn) and North Tropical Zone (NTrZ) there are convective storms, cyclones and anticyclones at nearby latitudes and atmospheric waves. In this complex region there is a large anticyclone the North Tropical Oval (NTrO) located at 19ºN planetographic latitude that persists since at least 2006 and it is one of the longest-lived anticyclonic ovals in the planet, following the Great Red Spot and oval BA. The NTrO has endured a complex dynamic history. It experienced one major merger with other oval in February 2013. It has also suffered color changes, with a change from white to red in September 2013 and then, in December 2014, back to white, but with a remaining external red ring. Moreover, it has survived major disturbances of the region. A North Temperate Belt Disturbance (NTBd) occurred in October 2016, which fully covered the oval, leaving it undistinguishable for months. When it reappeared, it was at the expected longitude from its previous longitudinal tracking with a similar appearance, a white large oval and same color and morphology from 2017 to 2021. It also survived the NTB disturbances that occurred in 2012 and 2020. In 2020 the region shows several other ovals in the vicinity so observations in 2021 will probably be able to show interactions between the NTrO and these new ovals. To describe the historic evolution of this anticyclone we use JunoCam, Hubble Space Telescope (HST), IOPW database and PlanetCam-UPV/EHU multi-wavelength observations. We have retrieved a very complete track of the oval with major changes in its drift rate in specific periods of time. JunoCam and HST images have been used to measure its size and internal rotation obtaining a mean value of (10,500±1,000) x (5,800±600) km for the size and a mean relative vorticity of -(2±1)·10-5s-1. While GRS and BA have higher vorticity values than their environments, the NTrO’s vorticity is nearly the same as the ambient vorticity of its surroundings. This may suggest that this oval is probably sustained by the zonal jets confining it. Using HST and PlanetCam observations, we have characterized its color changes measuring the color and altitude-opacity indices. The results obtained for these indices show that the oval is higher and has redder clouds than its environment but has lower cloud tops than other large ovals like the GRS, and it is less red than the GRS and oval BA. Despite the external changes, including mergers and planetary-scale disturbances, and internal ones, in the form of morphology, altitude and color changes, none of them destroyed the vortex. The main characteristics of the oval remain unaltered. The drift rate and vorticity are visibly connected to its latitudinal location. The stability of the vortex to all the different changes of the area and its latitudinal changes suggest that the vortex is sustained by the atmosphere at levels much deeper than the observable cloud level.

Drolshagen, E., et al., [Context] In meteor physics, the luminous efficiency τ is used to convert the meteor's magnitude to the corresponding meteoroid's mass. However, a lack of sufficiently accurate verification methods or adequate laboratory tests mean that discussions around this parameter are a subject of controversy. [Aims] In this work, we aim to use meteor data obtained by the Fireball Recovery and InterPlanetary Observation to calculate the luminous efficiencies of the recorded meteors. We also show the limitations of the methods presented herein. [Methods] Deceleration-based formulas were used to calculate the masses of the pre-atmospheric meteoroids. These can in turn be compared to the meteor brightnesses to assess the luminous efficiencies of the recorded objects. Fragmentation of the meteoroids is not considered within this model. Good measurements of the meteor deceleration are required. [Results] We find τ-values, as well as the shape change coefficients, of 294 meteors and fireballs with determined masses in the range of 10-6-100 kg. The derived τ-values have a median of τmedian = 2.17%. Most of them are of the order of 0.1-10%. We present how our values are obtained, compare them with data reported in the literature, and discuss several methods. A dependence of τ on the pre-atmospheric velocity of the meteor, ve, is noticeable with a relation of τ = 0.0023 ve2.3. Furthermore, a dependence of τ on the initial meteoroid mass, Me, is found with negative linear behaviour in log-log space: τ = 0.48 Me-0.47. [Conclusions] The higher luminous efficiency of fast meteors could be explained by the higher amount of energy released. Fast meteoroids produce additional emission lines that radiate more efficiently in specific wavelengths due to the appearance of the so-called second component of higher temperature. Furthermore, the negative dependence of τ on Me implies that the radiation of smaller meteoroids is more efficient. The results of this study also show the limitations of the ablation-based model for the determination of the luminous efficiency.

Dust is the main driver of Mars' atmospheric variability. The determination of Martian dust aerosol properties is of high relevance for radiative modelling and calculating its weather forcing. In particular, the light scattering behaviour at intermediate and large scattering angles can provide valuable information regarding the airborne dust particle shape. The angular distribution of sky brightness observed by the Mars Science Laboratory engineering cameras (Navcam and Hazcam) is used here to characterise the atmospheric dust single scattering phase function and to constrain the shape of the particles. An iterative radiative transfer based retrieval method was implemented in order to determine the aerosol modelling parameters which best reproduce the observed sky radiance as a function of the scattering angle in the solar almucantar plane. The aerosol models considered in this study for retrieving dust radiative properties were an analytical three term Double Henyey-Greenstein (DHG) phase function, T-matrix calculations for cylindrical particles with different diameter-to-length (D/L) aspect ratios and experimental phase functions from laboratory measurements of several Martian dust analogue samples. Results of this study returned mean DHG phase function parameter values g1 = 0.889 ± 0.098, g2 = 0.094 ± 0.250, α = 0.743 ± 0.106; generating a phase function with an asymmetry parameter of g = 0.673 ± 0.081 (in line with Wolff et al., 2009). Although differences were observed during the low opacity aphelion season (lower forward scattering values, presence of a peak in the backward region) compared to the rest of the year, no clear evidences of seasonal behaviour or interannual variability were derived. The obtained average D/L aspect ratios for T-matrix calculated cylindrical particles were 0.70 ± 0.20 and 1.90 ± 0.20 (similar to Wolff et al., 2001), and the best fitting Martian dust analogue corresponded to the basalt sample (in agreement with Dabrowska et al., 2015).

We report the discovery of a large ($\sim$8500 km diameter) infrared-bright storm at Neptune's equator in June 2017. We tracked the storm over a period of 7 months with high-cadence infrared snapshot imaging, carried out on 14 nights at the 10 meter Keck II telescope and 17 nights at the Shane 120 inch reflector at Lick Observatory. The cloud feature was larger and more persistent than any equatorial clouds seen before on Neptune, remaining intermittently active from at least 10 June to 31 December 2017. Our Keck and Lick observations were augmented by very high-cadence images from the amateur community, which permitted the determination of accurate drift rates for the cloud feature. Its zonal drift speed was variable from 10 June to at least 25 July, but remained a constant $237.4 \pm 0.2$ m s$^{-1}$ from 30 September until at least 15 November. The pressure of the cloud top was determined from radiative transfer calculations to be 0.3-0.6 bar; this value remained constant over the course of the observations. Multiple cloud break-up events, in which a bright cloud band wrapped around Neptune's equator, were observed over the course of our observations. No "dark spot" vortices were seen near the equator in HST imaging on 6 and 7 October. The size and pressure of the storm are consistent with moist convection or a planetary-scale wave as the energy source of convective upwelling, but more modeling is required to determine the driver of this equatorial disturbance as well as the triggers for and dynamics of the observed cloud break-up events., 42 pages, 14 figures, 6 tables; Accepted to Icarus

In this paper we show that Sun-viewing images obtained by the Mars Science Laboratory (MSL) Navigation Cameras (Navcam) can be used for retrieving the dust optical depth and constrain the aerosol physical properties at Gale Crater by evaluating the sky brightness as a function of the scattering angle. We have used 65 Sun-pointing images covering a period of almost three Martian years, from MSL mission sol 21 to sol 1646 (MY 31 to 33). Radiometric calibration and geometric reduction were performed on MSL Navcam raw image data records to provide the observed sky radiance as a function of the scattering angle for the near-Sun region (scattering angle from 4° to 30°). These curves were fitted with a multiple scattering radiative transfer model for a plane-parallel Martian atmosphere model using the discrete ordinates method. Modelled sky brightness curves were generated as a function of two parameters: the aerosol particle size distribution effective radius and the dust column optical depth at the surface. A retrieval scheme was implemented for deriving the parameters that generated the best fitting curve under a least-square error criterion. The obtained results present a good agreement with previous work, showing the seasonal dependence of both dust column optical depth and the effective particle radius.

Jupiter’s Great Red Spot (GRS), a giant anticyclone, is the largest and longest-lived of all the vortices observed in planetary atmospheres. During its history, the GRS has shrunk to half its size since 1879, and encountered many smaller anticyclones and other dynamical features that might tend to erode it. In 2018-2020, while having a historically small size, its structure and even its survival appeared to be threatened when a series of anticyclones moving in from the east tore off large fragments of the red area and distorted its shape. In this work we report observations of the dynamics of these interactions and show that as a result the GRS increased its internal rotation velocity, maintaining its vorticity but decreasing its visible area, and suffering a transient change in its otherwise steady 90-day oscillation in longitude. From a radiative transfer analysis and numerical simulations of the dynamics we show that the interactions affected the upper cloud tops of the GRS. We argue that the intense vorticity of the GRS, together with its larger size and depth compared to the interacting vortices, guarantees its long lifetime. This work has been supported by the Spanish project AYA2015-65041-P and PID2019-109467GB-I00 (MINECO/ FEDER, UE) and Grupos Gobierno Vasco IT1366-19. PI acknowledges a PhD scholarship from Gobierno Vasco. EGM is Serra Hunter Fellow at UPC. This work used data acquired from the NASA/ESA HST Space Telescope, asso- ciated with OPAL program (PI: Simon, GO13937), and archived by the Space Telescope Science Institute, which is operated by the Association of Universi- ties for Research in Astronomy, Inc., under NASA contract NAS 5–26,555. All maps are available at http://dx.doi. org/10.17909/T9G593. PlanetCam ob- servations were collected at the Centro Astronómico Hispánico en Andalucía (CAHA), operated jointly by the Insti- tuto de Astrofisica de Andalucia (CSIC) and the Andalusian Universities (Junta de Andalucía). EGM, MS, APG, MAC and ASL thankfully acknowledge the computer resources at Mare Nostrum and the technical support provided by Barcelona Supercomputing Center (AECT-2019-2-0006). This research has made use of the USGS Integrated Software for Imagers and Spectrometers (ISIS). We appreciate the contribution from all observers cited in TableS1 for his fundamental contribution to this study with Jupiter images obtained with high dedication and skill. GSO and TM were supported by NASA with funds distributed to the Jet Propulsion Laboratory, California Institute of Technology.

We present the first systematic study of clouds observed during twilight on Mars. We analyze images obtained by the Visual Monitoring Camera (VMC) on Mars Express between 2007 and 2020. Using an automated retrieval algorithm we found 407 cases of clouds observed at twilight, in which the geometry of the observations allows to derive the minimum altitude, revealing that many of these clouds are in the mesosphere (above 40km and up to 90km). The majority of these mesospheric clouds were detected in mid-latitudes at local autumn and winter, a new trend only hinted at by previous studies. In particular, we find a massive concentration of clouds in the southern mid-latitudes between Terra Cimmeria and Aonia, a region where high altitude events have been previously observed. We propose that there is an unknown mechanism in these regions that enhances the probability to host high altitude clouds around the southern winter solstice.

We report a previously unnoticed annually repeating phenomenon consisting of the daily formation of an extremely elongated cloud extending as far as 1,800 km westward from Arsia Mons. It takes place in the solar longitude (Ls) range of ∼220°-320°, around the Southern solstice. We study this Arsia Mons Elongated Cloud (AMEC) using images from different orbiters, including ESA Mars Express, NASA MAVEN, Viking 2, MRO, and ISRO Mars Orbiter Mission (MOM). We study the AMEC in detail in Martian year (MY) 34 in terms of local time and Ls and find that it exhibits a very rapid daily cycle: the cloud growth starts before sunrise on the western slope of the volcano, followed by a westward expansion that lasts 2.5 h with a velocity of around 170 m/s in the mesosphere (∼45 km over the areoid). The cloud formation then ceases, detaches from its formation point, and continues moving westward until it evaporates before the afternoon, when most sun synchronous orbiters make observations. Moreover, we comparatively study observations from different years (i.e., MYs 29-34) in search of interannual variations and find that in MY33 the cloud exhibits lower activity, while in MY34 the beginning of its formation was delayed compared with other years, most likely due to the Global Dust Storm. This phenomenon takes place in a season known for the general lack of clouds on Mars. In this paper we focus on observations, and a theoretical interpretation will be the subject of a separate paper.

The Great Red Spot (GRS) of Jupiter is a large anticyclonic vortex present in the Jovian atmosphere. First observed in the XVII century, it is almost constantly located at 22°S and it is arguably one of the main atmospheric phenomena in the Solar System. Despite having been widely studied, the nature of the chromophore species that provide its characteristic colour to the GRS’s upper clouds and hazes is still unclear, as well as its creation and destruction mechanisms.In this work we have analysed images provided by the Hubble Space Telescope’s Wide Field Camera 3 between 2015 and 2019, with a spectral coverage from the ultraviolet to the near infrared, including two methane absorption bands. These images have undergone a photometric process of cross calibration, ensuring a consistent correlation among the images corresponding to different visits and years. From such calibrated images, we have obtained the spectral reflectivity of the GRS and its surroundings, with particular emphasis on a few, dynamically interesting regions.We used the NEMESIS radiative transfer suite to retrieve the main atmospheric parameters (particle vertical and size distributions, refractive indices…) that are able to explain the observed spectral reflectivity of the selected regions. Here we report the spatial and temporal variations on such parameters and their implications on the GRS overall dynamics.

The ubiquitous dust aerosol particles in the atmosphere of Mars play a main role on the behaviour and evolution of its climate. By absorbing and scattering the incoming solar radiation, they modify the atmospheric thermal structure and dynamics. Dust radiative forcing calculations are of high relevance to understand Mars' overall atmospheric dynamics. The accuracy in determining internal radiation fields and the resulting atmospheric heating/cooling rates contribute to the uncertainties in these calculations.Radiative transfer schemes using 2-stream approximations are widely implemented in multiple Mars’ dynamical models and Global Circulation Models (GCMs). The uncertainties associated to this approximation are related to neglecting details of dust particles’ scattering phase function: the higher the number of streams considered, the better the accuracy of the scheme, although there is a persistent trade-off between accuracy and computational cost. The objective of this work is to evaluate the accuracy of dust aerosol radiative forcing estimations in the Martian atmosphere by multiple-stream schemes.Several scenarios covering the different atmospheric conditions during the Martian Year were simulated with different radiative transfer models, as well as other high-opacity dust storm scenarios. The atmosphere was discretised into 50 levels from 0 to 100 km, with atmospheric variables loaded from LMD’s Mars Climate Database (MCD). The visible and infrared spectral regions were divided into 12 bands, covering from 0.24 to 1,000 μm. Gaseous opacities were calculated with the correlated-k method, with absorption data retrieved from HITRAN. Dust aerosol radiative properties were derived using the wavelength-dependent properties reported by Wolff et al. (2006, 2009), with vertical distributions following a Conrath profile, and assuming a well-mixed dust scenario. Particle size (effective radius) and column dust opacity were given values to characterise every scenario. Finally, the calculated internal radiation fields and heating/cooling rates with the two-stream approximation code were compared with 4, 8, 16 and 32-stream solutions using the discrete ordinates method (DISORT).The comparison of the results with respect to the 32-stream model shows heating rate underestimations with average differences of about 2.7, 0.3, 0.1, and 0.1 K/sol for the 2-, 4-, 8-, and 16-stream models, respectively. Such differences tend to be larger when there is more dust is loaded into the atmosphere. On the other hand, the average computational times for 1 sol using the 4-, 8-, 16-, and 32-stream schemes are about 15, 25, 40 and 135 times longer than the 2-stream scheme, respectively.Future research prospects include the implementation of multiple-stream DISORT codes in Mars’ mesoscale dynamical models to investigate the accuracy of simulations of the atmospheric effects generated by local and regional dust storms.

In a recent work (Hernández-Bernal et al. 2020) we reported the existence and properties of the AMEC (Arsia Mons Elongated Cloud). This cloud appears every martian year around the southern solstice following a quick daily cycle, it expands up to 1800 km after sunrise and disappears before noon. While in the previous work we made an extensive observational study, a number of questions remain unsolved, including the specific specific set of atmospheric conditions that originates this particular cloud at this moment of the year, and why other near volcanoes do not exhibit analogous clouds. In this work we explore, based on models, the physical conditions of the atmosphere around Arsia Mons, such as temperature gradients, winds, and water vapor distribution, as a first step to try to understand this particular cloud.References:Hernández-Bernal, J., Sánchez-Lavega, A., Río-Gaztelurrutia, T. D., Ravanis, E., Cardesín-Moinelo, A., Connour, K., ... & Hauber, E. An Extremely Elongated Cloud over Arsia Mons Volcano on Mars: I. Life Cycle. Journal of Geophysical Research: Planets, DOI: 10.1029/2020JE006517

Because of its large size, fast rotation and multiple atmospheric jets, Jupiter’s atmosphere holds a large variety of vortices. A large anticyclone at 19ºN planetographic latitude persists since at least 2006 after a complex dynamic history. This North Tropical Oval (NTrO) is located in the transition region between the North Equatorial Band (NEBn) and North Tropical Zone (NTrZ) and it is one of the longest-lived anticyclonic oval in the planet, following the Great Red Spot and oval BA. The region where it is located has a strong latitudinal shear, which allows the formation of dark cyclones and usually white anticyclones that stay stable in latitude. The NTrO has survived for years after mergers and disturbances: in February 2013, it merged with another oval and some months later, in September 2013, its color changed from white to red and then, in December 2014, back to white with an external red ring. The oval also survived the North Temperate Belt Disturbance (October 2016) which fully covered the oval, leaving it unobservable for a short time. It reappeared at its expected longitude as a white large oval keeping the same color and morphology from 2017 to 2020. Using JunoCam, Hubble Space Telescope (HST) and PlanetCam-UPV/EHU multi-wavelength observations, we describe the historic evolution of this oval’s properties. We used JunoCam and HST images to measure its size and its internal rotation obtaining a mean value of (10,500±1,000) x (5,800±600) km for the size and a mean relative vorticity of -(2±1)·10-5s-1. Contrarily to GRS and BA, which have higher vorticity values than their surroundings, the NTrO’s vorticity is nearly the same as the ambient vorticity of the area, which suggests that this oval is probably sustained by the zonal jets confining it. We also used HST and PlanetCam observations to characterize its color changes. The color and the altitude-opacity indices show that the oval is higher and has redder clouds than its environment but has lower cloud tops than other large ovals like the GRS, and it is less red than the GRS and oval BA. Despite the changes, mergers and disturbances experienced by the oval, its main characteristics remain unaltered and this suggests a vertically extended vortex with properties that could be related with the atmospheric dynamics below the observable cloud deck.

Convective storms on Jupiter usually develop in the cyclonic side of the jets or inside cyclones (Vasavada and Showman, 2005). On 31 May 2020 a convective storm developed inside a small cyclone (3º in longitudinal extent) in the South Temperate Belt at planetographic latitude 30ºS. The storm outbreak was captured by amateur astronomer Clyde Foster becoming widely known as Clyde’s spot. The storm was observed 2.5 days later by JunoCam with images displaying an apparent cyclonic structure with two main lobes and high-clouds observable in the methane absorption band. Analysis of these observations show the storm in a decaying phase with associated weak winds. Observations over the following months combined with prior observations (2 years) obtained by JunoCam, HST, IRTF and amateur observers show the long-term evolution of the cyclone before and after the convective eruption. The short-lived storm made the cyclone to display large changes in morphology and colour but not in its size or latitude, except for small fluctuations around a mean latitude and mean drift rate. Ground-based infrared observations at 5 μm show the region where the vortex was located characterized by a weakly warm radiance several months after the convective outbreak, indicating a relative clearing of clouds and haze. We have used the Explicit Planetary Isentropic-Coordinate (EPIC) numerical model (Dowling et. al., 1998) to simulate the cyclone and the effects of convective storms of different strengths and durations on it. These simulations were partially guided by our previous study of a similar convective storm in a different type of cyclone: an elongated structure known as the STB Ghost at the same latitude in 2018 (Iñurrigarro et. al., 2020). Both storms and cyclones were different in terms of their size, morphology and later evolution, but our simulations suggest that in both cases the convective eruptions were of similar power but with different lifetimes indicating that the energy source is water moist convection. We compare these storms and simulations with a similar convective storm observed in 1979 by Voyager 2 at 38ºS that quickly evolved into a Folded-Filamentary Region and investigate the outcome of convective storms at different latitudes from these simulations.References:Dowling et al., 1998. The Explicit Planetary Isentropic-Coordinate (EPIC) Atmospheric Model, Icarus, 132, 221-238.Iñurrigarro et al., 2020. Observations and numerical modelling of a convective disturbance in a large-scale cyclone in Jupiter’s South Temperate Belt, Icarus, 336, 113475.Vasavada and Showman, 2005. Jovian atmospheric dynamics: an update after Galileo and Cassini, Reports on Progress in Physics, 68, 1935-1996.