Dmitri Titov

Perennial water ice identified in the south polar cap of Mars.

The inventory of water and carbon dioxide reservoirs on Mars are important clues for understanding the geological, climatic and potentially exobiological evolution of the planet. From the early mapping observation of the permanent ice caps on the martian poles, the northern cap was believed to be mainly composed of water ice, whereas the southern cap was thought to be constituted of carbon dioxide ice. However, recent missions (NASA missions Mars Global Surveyor and Odyssey) have revealed surface structures, altimetry profiles, underlying buried hydrogen, and temperatures of the south polar regions that are thermodynamically consistent with a mixture of surface water ice and carbon dioxide. Here we present the first direct identification and mapping of both carbon dioxide and water ice in the martian high southern latitudes, at a resolution of 2 km, during the local summer, when the extent of the polar ice is at its minimum. We observe that this south polar cap contains perennial water ice in extended areas: as a small admixture to carbon dioxide in the bright regions; associated with dust, without carbon dioxide, at the edges of this bright cap; and, unexpectedly, in large areas tens of kilometres away from the bright cap.

A warm layer in Venus' cryosphere and high-altitude measurements of HF, HCl, H2O and HDO

Venus has thick clouds of H2SO4 aerosol particles extending from altitudes of 40 to 60 km. The 60–100 km region (the mesosphere) is a transition region between the 4 day retrograde superrotation at the top of the thick clouds and the solar–antisolar circulation in the thermosphere (above 100 km), which has upwelling over the subsolar point and transport to the nightside. The mesosphere has a light haze of variable optical thickness, with CO, SO2, HCl, HF, H2O and HDO as the most important minor gaseous constituents, but the vertical distribution of the haze and molecules is poorly known because previous descent probes began their measurements at or below 60 km. Here we report the detection of an extensive layer of warm air at altitudes 90–120 km on the night side that we interpret as the result of adiabatic heating during air subsidence. Such a strong temperature inversion was not expected, because the night side of Venus was otherwise so cold that it was named the ‘cryosphere’ above 100 km. We also measured the mesospheric distributions of HF, HCl, H2O and HDO. HCl is less abundant than reported 40 years ago. HDO/H2O is enhanced by a factor of ∼2.5 with respect to the lower atmosphere, and there is a general depletion of H2O around 80–90 km for which we have no explanation.

A dynamic upper atmosphere of Venus as revealed by VIRTIS on Venus Express

The upper atmosphere of a planet is a transition region in which energy is transferred between the deeper atmosphere and outer space. Molecular emissions from the upper atmosphere (90–120 km altitude) of Venus can be used to investigate the energetics and to trace the circulation of this hitherto little-studied region. Previous spacecraft and ground-based observations of infrared emission from CO2, O2 and NO have established that photochemical and dynamic activity controls the structure of the upper atmosphere of Venus. These data, however, have left unresolved the precise altitude of the emission owing to a lack of data and of an adequate observing geometry. Here we report measurements of day-side CO2 non-local thermodynamic equilibrium emission at 4.3 µm, extending from 90 to 120 km altitude, and of night-side O2 emission extending from 95 to 100 km. The CO2 emission peak occurs at ∼115 km and varies with solar zenith angle over a range of ∼10 km. This confirms previous modelling, and permits the beginning of a systematic study of the variability of the emission. The O2 peak emission happens at 96 km ± 1 km, which is consistent with three-body recombination of oxygen atoms transported from the day side by a global thermospheric sub-solar to anti-solar circulation, as previously predicted.

THE LAVOISIER MISSION : A SYSTEM OF DESCENT PROBE AND BALLOON FLOTILLA FOR GEOCHEMICAL INVESTIGATION OF THE DEEP ATMOSPHERE AND SURFACE OF VENUS

Abstract Lavoisier mission is a joint effort of eight European countries and a technological challenge aimed at investigating the lower atmosphere and the surface of Venus. The mission consists of a descent probe and three balloons to be deployed below the cloud deck. Its main scientific objectives may be summarized as following : (i) composition of the deep atmosphere : noble gas (elemental/isotopic), molecular species (elemental/ isotopic), oxygen fugacity; vertical/horizontal/temporal variability; (ii) infrared spectroscopy and radiometry (molecular composition, radiative transfer); (iii) dynamics of the atmosphere : p, T, acceleration measurements, balloon localization through VLBI, meteorological events signed by acoustic waves, atmospheric mixing as imprinted on radioactive tracers; (iv) surface morphology and mineralogy through near infrared imaging on dayside, surface temperature through NIR imaging on nightside. Additional tentative objectives are search for (a) atmospheric electrical activity (optically, radioelectrically, acoustically), (b) crustal outgassing and/or volcanic activity : acoustic activity, horizontal/vertical distribution of radioactive tracers, (c) seismic activity : acoustic waves transmitted from crust to atmosphere, and (d) remanent and/or intrinsic magnetic field. Lavoisier was proposed to ESA in response to the F2/F3 mission Announcement of Opportunity at the beginning of 2000, but it was not selected for the assessment study. A wide international partnership was created for this occasion, including Finland (FMI), France (IPSL, MAGIE, Universite Orsay, IPSN, INPG, CEA, IPGP, Obs. Paris-Meudon), Germany (MPAe, Univ. Muenster), Hungary (KFKI, Univ. Eotvos), Portugal (OAL), Russia (IKI), Spain (IAA), United Kingdom (Univ. Oxford).

Venus Express and Terrestrial Planet Climatology

After a delay of more than a decade, the exploration of Venus has resumed through the European Venus Express mission, now in orbit around the planet. The mission payload, its implementation in an elliptical polar orbit, and the science operations planned, all focus on outstanding problems associated with the atmosphere and climate of Venus. Many of these problems, such as understanding the extreme surface warming produced by the carbon dioxide-driven greenhouse effect, and the role of sulfate aerosols in the atmosphere, have resonances with climate-change issues on the Earth and Mars. As data on all three terrestrial planets accumulates, and models of the energy balance and general circulation of their atmospheres improve, it becomes increasingly possible to define and elucidate their behavior in a common, comparative framework. Venus Express seeks to contribute to progress in this area.

Venus Express Monitoring Camera Science Operations

The Venus Express mission was launched in late 2005 after a very short development time. The spacecraft was successfully ingested in Venus orbit in April 2006 and operations started shortly after. The Science Operations are coordinated by the Venus Express Science Operations Centre (VSOC) located in Madrid, Spain. However most of the work is done across Europe, in the Principal Investigator (PI) institutes. In the case of the Venus Express Monitoring Camera (VMC), it is done from Lindau in Germany, with some support provided by ESA. The planning is divided in three main cycles, namely long, medium and short term planning. In the long term planning cycle, the high level requirements are derived, and the science objectives defined. This provides a skeleton to the medium term planning cycle where most of the activities take place. Finally, very close to the actual operations there is the short term planning cycle, where only small changes can take place, mainly in refining details such as exposure times. In VMC, from the beginning of 2007, a new system is being used, based in past knowledge acquired from previous ESA missions, and in particular SMART-1. Within this system in the Medium term plan, science events are derived from the Long term plan science requirements, thus providing windows of opportunity for the science to be conducted. These windows are defined by optimum observation conditions, where the parameters are the observation geometries, available resources such as data or power, and environment constraints such as the sun position. Not being a completely new approach on ESA missions, the attempt here is to re-use a system, with a completely different set of requirements, and show that with few adjustments such system can provide extremely good results. This approach also has the bonus of years of live test and debugging. On top of the re-use of the concept, tools are also re-utilized to a great extent. In this case benefiting from a similar approach on the software development of the ESA planetary missions where software is reused across missions. In this paper we will show how it is possible, following the approach described, to reduce the amount of workload, and consequently the costs of operations, while keeping the same level of achievement, or even better, as more time is available to dedicate to analyze the science data.