The conditions in Venus’ upper mesosphere at around 120 km have some similarities to the upper mesosphere of Earth and Mars where ice clouds form. Here we show, using published satellite products and numerical modelling, that the upper mesosphere of Venus is sufficiently cold that both H2O and CO2 can condense to form particles. In fact, we show that there is likely to be a competition between the direct nucleation of particles from the gas phase (homogeneous nucleation) and the nucleation on meteoric smoke particles (MSPs, heterogeneous nucleation). Amorphous solid water particles (ASW) are likely to nucleate first, resulting in clouds of nano-scaled particles at around 120 km globally. The temperatures can then become sufficiently low that CO2 particles can nucleate either on MSPs or on ASW particles (>30% of the time poleward of 60°). Since the main component of the atmosphere is CO2 these particles will grow and sediment on a timescale of 10-20 minutes. Mie calculations show that these Venusian mesospheric clouds (VMCs) should be observable by contemporary satellite instruments, although their short lifetime means that the probability of detection is small. We suggest that VMCs are important for the redistribution of meteoric smoke and may serve as a cold-trap, removing some water vapour from the very upper mesosphere of Venus, through the growth and sedimentation of cloud particles, and possibly reducing the loss of water to space.

The Europlanet H2020 program started on 1/9/2015 for 4 years. It includes an activity to adapt Virtual Observatory (VO) techniques to Planetary Science data called VESPA. The objective is to facilitate searches in big archives as well as sparse databases, to provide simple data access and on-line visualization, and to allow small data providers to make their data available in an interoperable environment with minimum effort. The VESPA system has been hugely improved during the first three years of Europlanet H2020: the infrastructure has been upgraded to describe data in many fields more accurately; the main user search interface (http://vespa.obspm.fr) has been redesigned to provide more flexibility; alternative ways to access Planetary Science data services from VO tools have been implemented; VO tools are being improved to handle specificities of Solar System data, e.g. measurements in reflected light, coordinate systems, etc. Current steps include the development of a connection between the VO world and GIS tools, and integration of Heliophysics, planetary plasmas, and mineral spectroscopy data to support of the analysis of observations. Existing data services have been updated, and new ones have been designed. The global objective is already overstepped, with 42 services open (including ESA’s PSA) and ~15 more being finalized. A procedure to install data services has been documented, and hands-on sessions are organized twice a year at EGU and EPSC; this is intended to favour the installation of services by individual research teams, e.g. to distribute derived data related to a published study. In complement, regular discussions are held with big data providers, starting with space agencies (IPDA). Common projects with PDS have been engaged, with the goal to connect PDS4 and EPN-TAP based on a local data dictionary. In parallel, a Solar System Interest Group has been established in IVOA; the goal is here to adapt existing astronomy standards to Planetary Science. The Europlanet 2020 Research Infrastructure project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 654208. [1] Erard et al 2014, Astronomy & Computing 7-8, 71-80. http://arxiv.org/abs/1407.4886