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Context. In February 2018, the international community working on the investigation and exploration of the atmosphere and surface of Mars met at ESAC near Madrid for a few days conference, organized and funded by the project UPWARDS (“Understanding Planet Mars With Advanced Remote- ensing Datasets and Synergistic Studies”, www.upwards-mars.eu) of the EU Horizon 2020 program. This project, and that conference, were devoted to promote the scientific exploitation of Mars Express data and to revisiting and sharing results from this mission, in preparation for the upcoming new European mission to Mars, the ExoMars-2016. The meeting approximately coincided in time with the end of the aerobraking phase of the Trace Gas Orbiter (TGO), which is the orbital element of ExoMars-2016. The TGO science phase started on 21 April 2018. This special issue of Icarus contains eleven papers which report original research results presented at the meeting or based on those presentations. This is obviously not an exhaustive representation of what was presented in Madrid, as other results have been published elsewhere. But they all share the motto of the meeting - from MEX to TGO - by presenting highlights of almost 15 years of Mars EXpress science legacy and new tools and methods for data analysis, thus paving the way for TGO observations and collaboration between two spacecraft. We think this is a valuable approach which, if properly and timely coordinated, can be very fruitful and should be promoted on every new space mission. The UPWARDS project could be considered as a bridge facilitating transition between two ESA missions, building team connections and enhancing science return from both missions. The second goal of the UPWARDS project, now more in the scientific than in the programmatic realm, was to exploit synergies between different teams in a cross-disciplinary approach, looking for an integral vision of the planet in an attempt to unveil couplings between different regions. In the meeting mentioned above, there were investigations from the subsoil and the surface, to the lower atmosphere's composition and dust, to the water cycle and up to the thermospheric structure and escape to space. In this framework, this issue presents its 11 contributions ordered in this bottom-to-top vision of the atmosphere., We want to acknowledge ESA for successful operations of the Mars Express and the TGO spacecrafts. The project UPWARDS-633127 was funded by the European Union's Horizon 2020 research and innovation Programme.

After 16 years in orbit Mars Express remains one of ESA’s most scientifically productive Solar System missions which publication record now exceeds 1270 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 studies suggest geological evidence of a planet-wide groundwater system on Mars and surface clay formation during short-term warmer and wetter conditions on a largely cold ancient Mars that might indicate a change in our understanding of early Mars climate. HRSC team released first set of multi-orbit Digital Elevation Model (DEM) of the MC-11 quadrangle and the Southern polar cap with 50 m/px resolution. Mars Express observations and experimental teams provided essential contribution to the selection of the Mars-2020 landing sites and supporting characterization of potential landing sites for the Chinese HX-1 mission. Following recent discovery of subglacial liquid water underneath the Southern polar layered deposits the MARSIS radar continues searching for subsurface water pockets.One-and-half decade of monitoring of 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. The observed ozone climatology demonstrate significant discrepancies with model predictions indicating the need for models improvement. In 2018 PFS confirmed observations of a methane abundance “spike” in the Gale crater observed in situ by the Curiosity Rover. Recent similar quasi-simultaneous observations were in disagreement, thus indicating that the methane “enigma” continues. This poses a significant challenge to both observers and modelers. The radio-science experiment MaRS revealed fine structure of the boundary layer. Its depth varies from 2 km in topographic lows to ~10 km over highlands.Observations of the ion escape during complete solar cycle revealed that ion escape can be responsible for removal of about 10 mbar over Mars history that implies existence of other more effective escape channels. The structure of the ionosphere derived from MARSIS and MaRS sounding was found to be significantly affected by the solar activity, the crustal magnetic field. The 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. Expansion of the ionosphere was also observed during the global dust storm. Ionospheric models aim at creating user-friendly data base of plasma parameters that would be of great service to the planetary community.The “gyroless” attitude control and operations mode of the spacecraft operates flawlessly since April 2018. Aging batteries impose more and more limitations on science operations during eclipse seasons. The mission is now confirmed till the end of 2020 and notionally extended till the end of 2022. The talk will give the Mars Express status, review the recent science highlights, and outline future plans including synergistic science with TGO.

More than three decades have passed since the publication of the last review of the Venus clouds and hazes. The paper published in 1983 in the Venus book summarized the discoveries and findings of the US Pioneer Venus and a series of Soviet Venera spacecraft (Esposito et al. in Venus, p. 484, 1983). Due to the emphasis on in-situ investigations from descent probes, those missions established the basic features of the Venus cloud system, its vertical structure, composition and microphysical properties. Since then, significant progress in understanding of the Venus clouds has been achieved due to exploitation of new observation techniques onboard Galileo and Messenger flyby spacecraft and Venus Express and Akatsuki orbiters. They included detailed investigation of the mesospheric hazes in solar and stellar occultation geometry applied in the broad spectral range from UV to thermal IR. Imaging spectroscopy in the near-IR transparency “windows” on the night side opened a new and very effective way of sounding the deep atmosphere. This technique together with near-simultaneous UV imaging enabled comprehensive study of the cloud morphology from the cloud top to its deep layers. Venus Express operated from April 2006 until December 2014 and provided a continuous data set characterizing Venus clouds and hazes over a time span of almost 14 Venus years thus enabling a detailed study of temporal and spatial variability. The polar orbit of Venus Express allowed complete latitudinal coverage. These studies are being complemented by JAXA Akatsuki orbiter that began observations in May 2016. This paper reviews the current status of our knowledge of the Venus cloud system focusing mainly on the results acquired after the Venera, Pioneer Venus and Vega missions.

From the discovery that Venus has an atmosphere during the 1761 transit by M. Lomonosov to the current exploration of the planet by the Akatsuki orbiter, we continue to learn about the planet’s extreme climate and weather. This chapter attempts to provide a comprehensive but by no means exhaustive review of the results of the atmospheric thermal structure and radiative balance since the earlier works published in Venus and Venus II books from recent spacecraft and Earth based investigations and summarizes the gaps in our current knowledge. There have been no in-situ measurements of the deep Venus atmosphere since the flights of the two VeGa balloons and landers in 1985 (Sagdeev et al., Science 231:1411–1414, 1986). Thus, most of the new information about the atmospheric thermal structure has come from different remote sensing (Earth based and spacecraft) techniques using occultations (solar infrared, stellar ultraviolet and orbiter radio occultations), spectroscopy and microwave, short wave and thermal infrared emissions. The results are restricted to altitudes higher than about 40 km, except for one investigation of the near surface static stability inferred by Meadows and Crisp (J. Geophys. Res. 101:4595–4622, 1996) from 1 $\upmu$ m observations from Earth. Little information about the lower atmospheric structure is possible below about 40 km altitude from radio occultations due to large bending angles. The gaps in our knowledge include spectral albedo variations over time, vertical variation of the bulk composition of the atmosphere (mean molecular weight), the identity, properties and abundances of absorbers of incident solar radiation in the clouds. The causes of opacity variations in the nightside cloud cover and vertical gradients in the deep atmosphere bulk composition and its impact on static stability are also in need of critical studies. The knowledge gaps and questions about Venus and its atmosphere provide the incentive for obtaining the necessary measurements to understand the planet, which can provide some clues to learn about terrestrial exoplanets.

Accepted: 2014-12-04, 資料番号: SA1150126000

The Venus Monitoring Camera (VMC) acquired a set of ultraviolet (UV) images during the Venus Express mission unprecedented in its duration from May 2006 to September 2013. Here we present the results of digital tracking of the cloud features in the upper cloud layer at latitudes 25–75°S using images from 257 orbits with the best spatial coverage. The method relies on analysis of correlations between pairs of UV images separated in time. The bulk of data processed allows us to clarify the reasons why the mid-latitude jet is not always present in latitudinal wind profiles. Comparing VMC images with wind velocity fields we found a relationship between cloud morphology at middle latitudes and the circulation. The vector field in middle latitudes depends on the presence of a contrast global streak in the cloud morphology tilted with respect to latitude circles. The angle of the flow deflection (the angle between the wind velocity and latitudinal circles) and the difference of the zonal velocity on the opposite sides of the streak are in direct relationship to the angle between the streak and latitude circles. During such orbits the jet bulge does not appear in the latitudinal profile of the zonal wind component. Otherwise a zonal flow with small changes of the meridional velocity dominates in middle latitudes and manifests itself as a jet bulge. The relationship between the cloud cover morphology and circulation peculiarities can be attributed to the motion of global cloud features, like the Y-feature. We prepared plots of zonal and meridional velocities averaged with respect to the entire observation period. The average zonal velocity has a diurnal maximum at 15:00 local solar time and at 40°S. The meridional velocity reaches its maximum between 13:00 and 16:00 and at 50°S. The velocities obtained by the digital method are in good agreement with results of the visual method in the middle latitudes published earlier by Khatuntsev et al. (2013) .

We report on attempts to find the ongoing volcanic activity from nearinfrared night-time observations with the Venus Monitoring Camera (VMC) onboard of Venus Express. Here we consider VMC images of the areas of Maat Mons volcano and its vicinities, which, as it follows from analysis of the Magellan data, show evidence of geologically very recent volcanism. Analysis of VMC images taken in 12 observation sessions during the time period from 31 Oct 2007 to 15 Jun 2009 did not reveal any suspicious high-emission spots which could be signatures of the presently ongoing volcanic eruptions.We compare this time sequence of observations with the history of eruptions of volcano Mauna Loa, Hawaii, in the 20th century. This comparison shows that if Maat Mons volcano had the eruption history similar to that of Mauna Loa, the probability to observe an eruption in this VMC observation sequence would be about 8%, meaning that the absence of detection does not mean that Maat is not active in the present epoch. These estimates do not consider the effect of absorption and blurring of the thermal radiation coming from Venus surface by the planet atmosphere and clouds, which decreases detectability of thermal signature of fresh lavas. To assess the role of this effect we simulated near-infrared images of the study area with artificially added circular and rectangular (with different aspect ratios) lava flows having surface temperature 1000K and various areas. These simulations showed that 1 km² lava flows should be marginally seen by VMC. An increase of the lava surface area to 2 – 3km² makes them visible on the plains and increase of the area to 4 – 5km² makes them visible even in deep rift zones. Typical individual lava flows on Mauna Loa are a few km², however, they often have been formed during weeks to months and the instantaneous size of the hot flow surface was usually much smaller. Thus the detection probability is significantly lower than 8%, but it is far from negligible. Our consideration suggests that further search of Maat Mons area and other areas including young rift zones makes sense and should be continued. More effective search could be done if observations simultaneously cover most part of the night side of Venus for relatively long (years) time of continuous observations.

Since the discovery of ultraviolet markings on Venus, their observations have been a powerful tool to study the morphology, motions and dynamical state at the cloud top level. Here we present the results of investigation of the cloud top morphology performed by the Venus Monitoring Camera (VMC) during more than 3 years of the Venus Express mission. The camera acquires images in four narrow-band filters centered at 365, 513, 965 and 1010 nm with spatial resolution from 50 km at apocentre to a few hundred of meters at pericentre. The VMC experiment provides a significant improvement in the Venus imaging as compared to the capabilities of the earlier missions. The camera discovered new cloud features like bright “lace clouds” and cloud columns at the low latitudes, dark polar oval and narrow circular and spiral “grooves” in the polar regions, different types of waves at the high latitudes. The VMC observations revealed detailed structure of the sub-solar region and the afternoon convective wake, the bow-shape features and convective cells, the mid-latitude transition region and the “polar cap”. The polar orbit of the satellite enables for the first time nadir viewing of the Southern polar regions and an opportunity to zoom in on the planet. The experiment returned numerous images of the Venus limb and documented global and local brightening events. VMC provided almost continuous monitoring of the planet with high temporal resolution that allowed one to follow changes in the cloud morphology at various scales. We present the in-flight performance of the instrument and focus in particular on the data from the ultraviolet channel, centered at the characteristic wavelength of the unknown UV absorber that yields the highest contrasts on the cloud top. Low latitudes are dominated by relatively dark clouds that have mottled and fragmented appearance clearly indicating convective activity in the sub-solar region. At ∼50° latitude this pattern gives way to streaky clouds suggesting that horizontal, almost laminar, flow prevails here. Poleward from about 60°S the planet is covered by almost featureless bright polar hood sometimes crossed by dark narrow (∼300 km) spiral or circular structures. This global cloud pattern can change on time scales of a few days resulting in global and local “brightening events” when the bright haze can extend far into low latitudes and/or increase its brightness by 30%. Close-up snapshots reveal plenty of morphological details like convective cells, cloud streaks, cumulus-like columns, wave trains. Different kinds of small scale waves are frequently observed at the cloud top. The wave activity is mainly observed in the 65–80° latitude band and is in particular concentrated in the region of Ishtar Terra that suggests their possible orographic origin. The VMC observations have important implications for the problems of the unknown UV absorber, microphysical processes, dynamics and radiative energy balance at the cloud tops. They are only briefly discussed in the paper, but each of them will be the subject of a dedicated study.

International audience; High resolution images of Venus Northern hemisphere obtained with the Venus Monitoring Camera (VMC/VEx) allow studying small-scale dynamical phenomena at the cloud tops (∼62-70 km altitude) including features like wave trains. A systematic visual search of these waves was performed; more than 1500 orbits were analyzed and wave patterns were observed in more than 300 images. Four types of waves were identified in VMC images on the base of their morphology: long, medium, short and irregular type waves. With the aim to characterize the wave types and their possible excitation source, we retrieved wave properties such as location (latitude and longitude), local time, solar zenith angle, packet length and width, orientation, and wavelength of each wave. The long type waves appear as long and narrow straight features extending more than a few hundreds kilometers and with wavelengths between 7 and 17 km. Medium type waves exhibit irregular wavefronts extending more than 100 km and with wavelengths in the range 8-21 km. Short wave packets have a width of several tens of kilometers and extend to few hundreds kilometers and are characterized by smaller wavelengths (3-16 km). Irregular wave fields appear to be the result of wave interference. The waves are often identified in all VMC filters and are mostly found in the cold collar region at high latitudes (60-80°N) and are concentrated above Ishtar Terra, a continental size highland that includes the highest mountain belts of the planet. The high speed of the Venus Express spacecraft close to the pericentre does not allow to measure phase speed of waves due to the short temporal interval between image pairs. The lack of information on phase velocities does not allow us to establish with absolute confidence the nature of these waves. However, by comparing the morphology and properties of the wave features observed in VMC images to those seen by previous observations it is reasonable to assume that the waves studied here are gravity waves.

International audience; Past exploration of Jupiter's diverse satellite system has forever changed our understanding of the unique environments to be found around gas giants, both in our solar system and beyond. The detailed investigation of three of Jupiter's Galilean satellites (Ganymede, Europa, and Callisto), which are believed to harbour subsurface water oceans, is central to elucidating the conditions for habitability of icy worlds in planetary systems in general. The study of the Jupiter system and the possible existence of habitable environments offer the best opportunity for understanding the origins and formation of the gas giants and their satellite systems. The JUpiter ICy moons Explorer (JUICE) mission, selected by ESA in May 2012 to be the first large mission within the Cosmic Vision Program 2015-2025, will perform detailed investigations of Jupiter and its system in all their inter-relations and complexity with particular emphasis on Ganymede as a planetary body and potential habitat. The investigations of the neighbouring moons, Europa and Callisto, will complete a comparative picture of the Galilean moons and their potential habitability. Here we describe the scientific motivation for this exciting new European-led exploration of the Jupiter system in the context of our current knowledge and future aspirations for exploration, and the paradigm it will bring in the study of giant (exo) planets in general. [All rights reserved Elsevier].

We investigated the Venus O2 visible nightglow with imagery from the Venus Monitoring Camera on Venus Express. Drawing from data collected between April 2007 and January 2011, we study the global distribution of this emission, discovered in the late 70s by the Venera 9 and 10 missions. The inferred limb-viewing intensities are on the order of 150 kiloRayleighs at the lower latitudes and seem to drop somewhat towards the poles. The emission is generally stable, although there are episodes when the intensities rise up to 500 kR. We compare a set of Venus Monitoring Camera observations with coincident measurements of the O2 nightglow at 1.27 {\mu}m made with the Visible and Infrared Thermal Imaging Spectrometer, also on Venus Express. From the evidence gathered in this and past works, we suggest a direct correlation between the instantaneous emissions from the two O2 nightglow systems. Possible implications regarding the uncertain origin of the atomic oxygen green line at 557.7 nm are noted., Comment: 7 pages, 3 figures

We present here the annual behavior of atmospheric water vapor on Mars, as observed by the OMEGA spectrometer on board Mars Express during its first martian year. We consider all the different features of the cycle of water vapor: temporal evolution, both at a seasonal and at a diurnal scale; longitudinal distribution; and the vertical profile, through the variations in the saturation height. We put our results into the context of the current knowledge on the water cycle through a systematic comparison with the already published datasets. The seasonal behavior is in very good agreement with past and simultaneous retrievals both qualitatively and quantitatively, within the uncertainties. The average water vapor abundance during the year is ∼10 pr. μm, with an imbalance between northern and southern hemisphere, in favor of the first. The maximum of activity, up to 60 pr. μm, occurs at high northern latitudes during local summer and shows the dominance of the northern polar cap within the driving processes of the water cycle. A corresponding maximum at southern polar latitudes during the local summer is present, but less structured and intense. It reaches ∼25 pr. μm at its peak. Global circulation has some influence in shaping the water cycle, but it is less prominent than the results from previous instruments suggest. No significant correlation between water vapor column density and local hour is detected. We can constrain the amount of water vapor exchanged between the surface and the atmosphere to few pr. μm. This is consistent with recent results by OMEGA and PFS-LW. The action of the regolith layer on the global water cycle seems to be minor, but it cannot be precisely constrained. The distribution of water vapor on the planet, after removing the topography, shows the already known two-maxima system, over Tharsis and Arabia Terra. However, the Arabia Terra increase is quite fragmented compared with previous observations. A deep zone of minimum separates the two regions. The saturation height of water vapor is mainly governed by the variations of insolation during the year. It is confined within 5–15 km from the surface at aphelion, while in the perihelion season it stretches up to 55 km of altitude.