Search

Venus appears to be an “alien” planet drastically and surprisingly different from the Earth. The early space missions revealed the world with remarkably hot, dense, cloudy, and very dynamic atmosphere filled with toxic species likely of volcanic origin. During more than 8 years of operations ESA’s Venus Express spacecraft performed a global survey of the atmosphere and plasma environment of our near neighbour. The mission delivered comprehensive data on the temperature structure, the atmospheric composition, the cloud morphology, the atmospheric dynamics, the solar wind interaction and the escape processes. Vertical profiles of the atmospheric temperature showed strong latitudinal trend in the mesosphere and upper troposphere correlated with the changes in the cloud top structure and suggesting convective instability in the main cloud deck at 50-60 km. Observations revealed significant latitudinal variations and temporal changes in the global cloud top morphology, which modulate the solar energy deposited in the atmosphere. The cloud top altitude varies from ~72 km in the low and middle latitudes to ~64 km in the polar region, correlated with decrease of the aerosol scale height from 4 ± 1.6 km to 1.7 ± 2.4 km, marking vast polar depression. UV imaging showed for the first time the middle latitudes and polar regions in unprecedented detail. In particular, the eye of the Southern polar vortex was found to be a strongly variable feature with complex dynamics. Solar occultation observations and deep atmosphere spectroscopy in spectral transparency “windows” mapped distribution of the major trace gases H2O, SO2, CO, COS and their variations above and below the clouds, revealing key features of the dynamical and chemical processes at work. A strong, an order of magnitude, increase in SO2 cloud top abundance with subsequent return to the previous concentration was monitored by Venus Express specrometres. This phenomenon can be explained either by a mighty volcanic eruption or atmospheric dynamics. Tracking of cloud features provided the most complete characterization of the mean atmospheric circulation as well as its variability. Low and middle latitudes show an almost constant with latitude zonal wind speed at the cloud tops and vertical wind shear of 2-3 m/s/km. Surprisingly the zonal wind speed was found to correlate with topography decreasing from 110±16 m/s above lowlands to 84±20 m/s at Aphrodite Terra suggesting decelerating effect of topographic highs. Towards the pole, the wind speed drops quickly and the apparent vertical shear vanishes. The meridional cloud top wind has poleward direction with the wind speed ranging from about 0 m/s at equator to about 15 m/s in the middle latitudes. A reverse equatorward flow was found about 20 km deeper in the middle cloud suggesting existence of a Hadley cell or action of thermal tides at the cloud level. Comparison of the thermal wind field derived from temperature sounding to the cloud-tracked winds confirms the validity of cyclostrophic balance, at least in the latitude range from 30S to 70S. The observations are supported by the General Circulation Models. Venus Express detected and mapped non-LTE infrared emissions in the lines of O2, NO, CO2, OH originating near the mesopause at 95-105 km. The data show that the peak intensity occurs in average close to the anti-solar point for O2 emission, which is consistent with current models of the thermospheric circulation. For almost complete solar cycle the Venus Express instruments continuously monitored the induced magnetic field and plasma environment and established the global escape rates of 3·1024s−1, 7·1024s−1, 8·1022s−1 for O+, H+, and He+ ions and identified the main acceleration process. For the first time it was shown that the reconnection process takes place in the tail of a non-magnetized body. It was confirmed that the lightning tentatively detected by Pioneer-Venus Orbiter indeed occurs on Venus. Thermal mapping of the surface in the near-IR spectral “windows” on the night side indicated the presence of recent volcanism on the planet, as does the high and strongly variable SO2 abundance. Variations in the thermal emissivity of the surface observed by the VIRTIS imaging spectrometer indicated compositional differences in lava flows at three hotspots. These anomalies were interpreted as a lack of surface weathering suggesting the flows to be younger than 2.5 million years indicating that Venus is actively resurfacing. The VMC camera provided evidence of transient bright spots on the surface that are consistent with the extrusion of lava flows that locally cause significantly elevated surface temperatures. The very strong spatial correlation of the transient bright spots with the extremely young Ganiki Chasma, their similarity to locations of rift-associated volcanism on Earth, provide strong evidence of their volcanic origin and suggests that Venus is currently geodynamically active. Alongside observations of Earth, Mars and Titan, observation of Venus allows the opportunity to study geophysical processes in a wide range of parameter space. Furthermore, Venus can be considered as an archetype of terrestrial exoplanets that emphasizes an important link to the quickly growing field of exoplanets research. The talk will give an overview of the Venus Express findings including recent results of data analysis, outline outstanding unsolved problems and provide a bridge, via the Akatsuki mission, to the missions to come in 2030s: EnVision, VERITAS and DAVINCI.

After 18 years in orbit Mars Express remains one of ESA’s most scientifically productive Solar System missions, with a publication record now exceeding 1450 papers. Characterization of the surface geology on a local-to-regional scale by HRSC, OMEGA and partner experiments on NASA spacecraft has allowed constraining land-forming processes in space and time. Recent studies characterized the geology of Jezero crater in great detail and provided Digital Elevation Model (DEM) of several equatorial regions at 50 m/px resolution. New maps and catalogues of surface minerals with 200 m/px resolution were released. MARSIS radar published new observations and analysis of the multiple subglacial water bodies underneath the Southern polar cap. Modelling suggested that the “ponds” can be composed of hypersaline perchlorate brines.Spectrometers and imagers SPICAM, PFS, OMEGA, HRSC and VMC continue adding to the longest record of atmospheric parameters such as temperature, dust loading, water vapor and ozone abundance, water ice and CO2 clouds distribution and observing transient phenomena. More than 27,000 ozone profiles derived from SPICAM UV spectra obtained in MY#26 through MY#28 were assimilated in the OpenMARS database. A new PFS “scan” mode of the spacecraft was designed and implemented to investigate diurnal variations of the atmospheric parameters. Observations of Tharsis region and Hellas basin contribute to mesoscale meteorology.ASPERA measurements together with MAVEN “deep dip” data enabled assessment of the conditions that lead to the formation of the dayside ionopause in the regions with and without strong crustal magnetic fields suggesting that the ionopause occurs where the total ionospheric pressure (magnetic + thermal) equals the upstream solar wind dynamic pressure.In 2021 Mars Express successfully performed two types of novel observations. In egress-only radio-occultations a two-way radio link was locked at a tangent altitude of about 50 km. This is well below the ionospheric peak and would allow perfect sounding of the entire ionosphere thus doubling the number of ionospheric soundings. MEX and TGO performed several test UHF occultations. The dual-spacecraft radio-occultation technique would allow much broader spatial distribution of the missions’ radio occultation profiles. Mars Express is extended till the end of 2022. A science case for the mission extension till the end of 2025 will be developed and submitted in March 2022. The talk will give the Mars Express status, review the recent science highlights, and outline future plans including synergistic science with TGO and other missions.

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.

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.

21st EGU General Assembly, EGU2019, proceedings from the conference held 7-12 April, 2019 in Vienna, Austria, id.11100, After 15 years in orbit Mars Express remains one of ESA's most scientifically productive Solar System missions whose publication record now exceeds 1200 papers. Characterization of the geological processes on a local-to-regional scale by HRSC, OMEGA and partner experiments on NASA spacecraft has allowed constraining land-forming processes in space and time. Recent results suggest episodic geological activity as well as the presence of large bodies of liquid water in several provinces (e.g. Eridania Planum, Terra Chimeria) in the early and middle Amazonian epoch and formation of vast sedimentary plains north of the Hellas basin. Mars Express observations and experimental teams provided essential contribution to the selection of the Mars-2020 landing sites. Recent discovery of subglacial liquid water underneath the Southern polar cap has proven that the mission science potential is still not exhausted. More than a decade-long record of the atmospheric parameters such as temperature, dust loading, water vapor and ozone abundance, water ice and CO2 clouds distribution, collected by SPICAM, PFS, OMEGA, HRSC and VMC together with subsequent modeling have provided key contributions to our understanding of the martian climate. Recent spectroscopic monitoring of the 2018 dust storm revealed dust properties, their spatial and temporal variations and atmospheric circulation. More than 10,000 crossings of the bow shock by Mars Express allowed ASPERA-3 to characterize complex behavior of the magnetic boundary topology as function of the solar EUV flux. Observations of the ion escape during complete solar cycle revealed important dependencies of the atmospheric erosion rate on parameters of the solar wind and EUV flux and established global energy balance between the solar wind and escaping ion flow. The observations showed that ion escape can be responsible for removal of about 10 mbar over the Mars history that implies existence of other more effective escape channels. The structure of the ionosphere sounded by the MARSIS radar and the MaRS radio science experiment was found to be significantly affected by the solar activity, the crustal magnetic field, as well as by the influx of meteorite and cometary dust. MARSIS and ASPERA-3 observations suggest that the sunlit ionosphere over the regions with strong crustal fields is denser and extends to higher altitudes as compared to the regions with no crustal anomalies. Several models of the upper atmosphere and plasma environment are being developed based on and in support of the collected experimental data. The models aim at creating user-friendly data base of plasma parameters similar to the Mars Climate Database that would be of great service to the planetary community. A significant recent achievement was the flawless transition to the >gyroless> attitude control and operations mode on the spacecraft, that would allow mitigating the onboard gyros aging and extending the mission lifetime. In November 2018 ESA's Science Programme Committee (SPC) confirmed the mission operations till the end of 2020 and notionally approved its extension till the end of 2022. The talk will give the Mars Express status, review the recent science highlights, and outline future plans focusing on synergistic science with TGO.

We study the 2018 Martian Global DustStorm (GDS 2018) over the Southern Polar Region using images obtained by the Visual Monitoring Camera (VMC) on board Mars Express during June and July 2018. Dust penetrated into the polar cap region but never covered the cap completely, and its spatial distribution was nonhomogeneous and rapidly changing. However, we detected long but narrow aerosol curved arcs with a length of 2,000-3,000 km traversing part of the cap and crossing the terminator into the night side. Tracking discrete dust clouds allowed measurements of their motions that were towards the terminator with velocities up to 100 m/s. The images of the dust projected into the Martian limb show maximum altitudes of around 70 km but with large spatial and temporal variations. We discuss these results in the context of the predictions of a numerical model for dust storm scenario.

1. IntroductionThe European Space Agency (ESA) mission ‘Mars Express’ (MEX) launched in 2003 equipped with seven instruments. The Visual Monitoring Camera (VMC) on board MEX was designed to monitor the release of the Beagle 2 lander, but was switched back on again in 2007. In the following years, in addition to helping engage the general public with the MEX mission [1] VMC images were used for atmospheric studies [2,3] and subsequently the camera was ‘upgraded’ to a scientific instrument in 2016. Hence, the mission ‘gained’ a scientific instrument in the form of the VMC. The scientific success [4] of this small camera is a part of the larger success story of Europe’s first Mars mission, serving as an example of how planetary missions can exceed and build upon their original expectations. This work details the journey of VMC from an engineering to a scientific instrument, including how VMC is operated, how the data is calibrated, and examples of the scientific work that has been undertaken with VMC data, images of which are exemplified in Figure 1.2. Instrument OperationsThe VMC is a 640x480 pixel camera with a large field of view (FOV) of ~40 x 31°. The wide FOV allows the camera to capture both the entire disk of Mars within the image and to perform observations over a wide portion of the limb. When taken in combination with the elliptical orbit of MEX, this enables observations at different local times and distances. VMC has a different data protocol and is offset from other instruments by 19°, and for these reasons cannot observe at the same time as other instruments on MEX. Since 2018, planning for the VMC has been integrated with planning for the other payload instruments, which takes place at the European Space Astronomy Centre (ESAC). This integration has increased both the quantity and the types of observations performed by VMC (Figures 2 and 3).3. Data CalibrationThe VMC team has performed in situ calibration for VMC since no on-ground calibration exists for the instrument (discussed in [5]). Observations of dark sky were taken to create a master dark-current file for dark-current correction. Dark-corrected images of flat portions of Mars taken at pericentre that were well and uniformly illuminated, as free as possible from large structures and as flat as possible were used to create a file for flat-field correction. The boresight offset of VMC has also been calculated by comparing the location of stars in VMC images with the stars’ known positions given by the SPICE geometry information system.4. Data Processing and ArchivingSince [5], the VMC pipeline has been updated in collaboration with the science team at UPV-EHU Bilbao. VMC data are dark-corrected, flat-fielded, and are now provided in raw, FITS and PNG formats. The VMC pipeline runs at ESAC and is utilised by the VMC science team, and the current dataset from 2007 to the present totals ~50,000 images distributed across ~3000 observations. VMC data for scientific usage have been prepared for ingestion into the Planetary Science Archives (PSA) over the summer of 2020. This will be the first science data release from the instrument, thereby augmenting the already extensive wealth of data obtained from Mars Express over the last 17 years. Data from the VMC instrument continue to be available for outreach purposes through Twitter and Flickr (@esamarswebcam, Flickr: https://www.flickr.com/photos/esa_marswebcam/).5. Scientific SuccessThe regional and global scale atmospheric dynamics of Mars are fast-paced and so a high temporal resolution of observations at various local times is required to help us understand and constrain how such dynamics develop. As previously mentioned, the wide FOV of VMC coupled with the highly elliptical orbit of MEX allows VMC to take observations at diverse local times and therefore to capture these large-scale atmospheric phenomena (Figure 4). VMC images are taken approximately every ~48 seconds depending on exposure time, and so the science team has been able to stack images from the same observation and also produce mosaics and videos showing the movements of aerosols. VMC data has been used for the analysis of the Arsia Mons cloud [6]; a recurrent double cyclone in the north polar region [7]; the 2018 global dust storm [8] and local dust storms in 2019 [9]; and ‘twilight clouds’ in the Martian night [10].References:[1] Ormston, T., et al. (2011). An ordinary camera in an extraordinary location: Outreach with the Mars Webcam. Acta Astronautica, 69, 703-713.[2] Sánchez-Lavega, A., et al. (2016). Limb clouds and dust on Mars from VMC-Mars Express images. DPS 48, 16-21 October 2016, 409-01.[3] Sánchez-Lavega, A., et al. (2018). Limb clouds and dust on Mars from images obtained by the Visual Monitoring Camera (VMC) onboard Mars Express. Icarus 299: 194-205.[4] Cardesín-Moinelo, A., et al. (2017). A “NEW” SCIENTIFIC CAMERA AROUND MARS, GETTING SCIENCE WITH VISUAL MONITORING CAMERA ONBOARD MARS EXPRESS. Sixth International Workshop on the Mars Atmosphere: Modelling and Observations, 17-20th January 2017, Granada, Spain.[5] Ravanis, E.M., et al. (2019). Mars Express Visual Monitoring Camera: New Operations and Data Processing for more Science. EPSC2019, 15-20 September, Geneva, Switzerland.[6] Hernández-Bernal et al. (2020) An Extremely Elongated Cloud over Arsia Mons Volcano on Mars: Life Cycle. Submitted to Journal of Geophysical Research.[7] Sánchez-Lavega, A., et al. (2018) A seasonally recurrent annular cyclone in Mars northern latitudes and observations of a companion vortex. Journal of Geophysical Research: Planets 123.11: 3020-3034[8] Hernández‐Bernal, J., et al. (2019). The 2018 Martian Global Dust Storm over the South Polar Region studied with MEx/VMC. Geophysical Research Letters 46.17-18: 10330-10337.[9] Sánchez-Lavega, A., et al. (2020). Patterns in textured dust storms in Mars North Pole. EPSC2020, 21 September – 9th October 2020, Virtual.[10] Hernández-Bernal, J. et al. (2020). A long term study of twilight clouds on Mars based on Mars Express VMC images. EPSC2020, 21 September – 9th October 2020, Virtual.

If Venus were a newly discovered exoplanet, it would be one of the most Earth-like yet identified. Its similarity in size, bulk density and cloud top temperatures give no clue to the hellish temperatures at its surface. Venus hosts an array of geological features as complex as Earth, but without its organisation, and sustains a chemically reactive atmosphere, but without life. Proposed in response to ESA’s M5 call, with enabling support from NASA, EnVision is currently in Phase A study for the next medium-class mission opportunity proceeding towards a final mission selection in summer 2021 for a launch in 2032. Here we discuss the science questions motivating the mission in more detail. Building on discoveries from Magellan, Venus Express and Akatsuki, EnVision will focus on three overarching questions: Is Venus geodynamically active? How did Venus arrive at its current state? How does the Venus climate work and how do the interior, surface and atmosphere interact? 1 – Is Venus geodynamically active? Venus should be geologically active today and its globally young surface implies extensive volcanic resurfacing, but whether this happened in episodic global events or in a continuous process of small-scale resurfacing is uncertain. Constraining the rate of volcanic and tectonic activity can reveal whether Venus occupies one of these end members, or lies somewhere on the spectrum between. Magellan radar image mosaic of a 550 km wide region of Lada Terra (47°S, 25°E) showing a system of radar-bright and dark lava flows breaching a ridge belt and ponding in a large radar-bright deposit covering 100,000 km². Ammavaru, the source caldera, lies 300 km to the west (JPL/Caltech). Understanding the tectonic regime driving resurfacing and heat loss is as important as knowing the rate of activity. The surface appears partitioned into areas of low strain bounded by narrow high strain margins. The abundance of steep slopes and landslides implies active uplift in these high strain areas, but existing data provide no constraint on the frequency of landslides or rates of tectonic movement. Are the low strain regions actively created and destroyed, like Earth’s oceanic plates, or simply mobilised locally? What is the significance of the global network of elevated rift systems and linear lowland wrinkle-ridged plains? Unique to Venus are coronae, quasi-circular volcano-tectonic features, typically 100–500 km across. Are they the surface expression of plumes, or magmatic intrusions, or subduction zones? The processes of weathering, mass wasting and aeolian transport are critical for understanding both the geological history and climatic evolution of Venus. Venus Express found anomalously high IR emissivities near suspected active volcanoes, interpreted as fresh, unweathered lava flows, but both their mineralogy and the weathering processes involved are unknown. Magellan detected several, probably impact-related, dune fields at the limit of its resolution, and found indirect evidence for globally distributed smale-scale ripples. 2 – How Did Venus Arrive at its Current State? The cratering record reveals that the Venus surface is, on average, under 1 Ga old. While some areas are likely active today, other regions, e.g. the tessera highlands, may be considerably older. Magellan data imply a variety of age relationships and long-term activity, with a non-random association between geological features and elevation, e.g. the uplands are consistently more deformed than the lowlands. Impact craters themselves show alteration to dark floors, perhaps from airfall deposits or magmatic resurfacing. Densely fractured plains (right) abutting tessera (bottom); both are embayed by younger plains (dark areas). A steep-sided volcanic dome (upper left) may be the source of the plains or unrelated to them, and older or younger than the tesserae. Magellan image at 46°N, 360°E, after Basilevsky and McGill (2007). Constraining the history is critical to understanding not only when and how resurfaced, but whether that activity has changed systematically through time. Were the plains formed in a short period by massive outpourings or by many thousands of small flows over their entire history? Or did many different mechanisms – including sedimentary processes – operate at different times and places? Globally, Venus exhibits perhaps even more tectonic deformation than Earth: what is its role in resurfacing the planet and have the regimes of tectonic deformation changed over time? How did tesserae, especially, accumulate their extraordinary degree of deformation? The interior of Venus is probably Earth-like, but not the same; its core size is poorly constrained by Magellan gravity data. These data are consistent with an organised pattern of mantle convection but lack the resolution necessary to connect it with geological-scale features. 3 - How does the Venus climate work and how do the Interior, Surface and Atmosphere Interact? How and why the atmospheres of two Earth-like planets evolved so differently is one of the many compelling reasons to study Venus, directly addressing the question of how our own world became habitable. Understanding its evolution depends on knowing the exchanges between its interior, surface and space. The lower/middle clouds of Venus as imaged by Akatsuki IR2 camera. Dark areas represent thicker clouds, which may represent volcanic plumes of ash or sulphate particulates. (JAXA/ISAS/DART/Damia Bouic) Models suggest that the clouds are maintained by a constant input of H2O and SO2, both of which vary considerably, perhaps because of volcanic emissions. Elevated D/H ratios indicate the loss of early oceans, but the ‘starting’ mantle D/H ratio is unknown. Identification of granites in the ancient highlands would support this inference, but the direct detection and characterisation of volcanic volatiles is key to inferring past climate evolution. Beyond the specific investigations outlined above, however, the most important unknown factor in determining the present day state of Venus and its atmosphere, and how it arrived at that state, is the interaction between the interior, surface and atmosphere: the whole being more than the sum of the parts. References Basilevsky and McGill (2007), Surface evolution of Venus, in Exploring Venus as a Terrestrial Planet, Geophysical Monograph Series 176, edited by L. W. Esposito, E. R. Stofan and T. E. Cravens, pp. 23-43, American Geophysical Union, Washington, DC

Starting in September 2018, a daily repeating extremely elongated cloud was observed extending from the Mars Arsia Mons volcano. We study this Arsia Mons Elongated Cloud (AMEC) using images from VMC, HRSC, and OMEGA on board Mars Express, IUVS on MAVEN, and MARCI on MRO. We study the daily cycle of this cloud, showing how the morphology and other parameters of the cloud evolved with local time. The cloud expands every morning from the western slope of the volcano, at a westward velocity of around 150m/s, and an altitude of around 30-40km over the local surface. Starting around 2.5 hours after sunrise (8.2 Local True Solar Time, LTST), the formation of the cloud resumes, and the existing cloud keeps moving westward, so it detaches from the volcano, until it evaporates in the following hours. At this time, the cloud has expanded to a length of around 1500km. Short time later, a new local cloud appears on the western slope of the volcano, starting around 9.5 LTST, and grows during the morning.This daily cycle repeated regularly for at least 90 sols in 2018, around Southern Solstice (Ls 240-300) in Martian Year (MY) 34. According with these and previous MEx/VMC observations, this elongated cloud is a seasonal phenomenon occurring around Southern Solstice every Martian Year. We study the interannual variability of this cloud, the influence of the Global Dust Storms in 2018 on the cloud’s properties (Sánchez-Lavega et al., Geophys. Res. Lett. 46, 2019), and its validity as a proxy for the global state of the Martian atmosphere (Sánchez-Lavega et al., J. Geophys. Res., 123, 3020, 2018). We discuss the physical mechanisms behind the formation of this peculiar cloud in Mars.

The Visual Monitoring Camera (VMC), or “the ESA Mars Webcam” on board ESA’s Mars Express (MEX) orbiter was originally designed as an engineering camera whose purpose was to monitor the separation of the Beagle-2 lander in 2003. Later, in 2007, the camera was switched on again for outreach purposes, with images regularly posted to Twitter (@esamarswebcam) and Flickr. Following the subsequent use of VMC data for Mars atmospheric science (Sánchez-Lavega et al., AAS/DPS, 48, 2016; Sánchez-Lavega et al., Icarus 299, 194-205, 2018) the VMC was designated a scientific instrument in 2016. No on-ground calibration exists for the VMC, so the VMC team have had to take initiative in order to perform in-flight calibration of the instrument. New observation planning procedures have been developed, as well as a new data processing pipeline hosted at the European Space Astronomy Centre (ESAC) in Madrid to maximise the scientific return of the instrument. The data is currently in the process of being archived in the Planetary Science Archive, for its wider use by the community.The MEX Science Ground Segment (SGS) team at ESAC maintains close collaboration with the VMC science team located at the University of the Basque Country (UPV-EHU) in Bilbao. The scientific studies undertaken with VMC camera data include monitoring of the global dust storm over the south pole in 2018 (Hernández-Bernal et al., J. Geophys. Res. Lett., 46, 10330–10337, 2019), analysis of twilight clouds (Hernández-Bernal et al., EPSC, 12, 2018), discovery of a seasonally recurrent double cyclone in the northern latitudes of Mars (Sánchez-Lavega et al., J. Geophys. Res., 123, 3020, 2018) and studies of an extremely elongated cloud over Arsia Mons (Hernández-Bernal et al., EGU, 2020). The scientific success of this “webcam” around Mars highlights how small cameras on planetary missions can yield high science return, which has implications for potential future CubeSat missions to Mars.