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EnVision Science Goals:

The dramatic discovery of volcanic hotspots in Venus Express data suggest that the next stage of Venus exploration must focus on its surface: the geological interface between its dense, hostile atmosphere and its Earth-like but puzzling interior. Magellan data reveal an incredible number of volcanoes, as well as rift systems, mountain belts, and a range of features still poorly understood, on a world with a crater count indicative of mean surface age of only 500 Ma, as young as Europe. EnVision is designed to build on ESA’s unequalled Earth Observation expertise to understand this complex world, by measuring the rate and nature of geological activity and its influence on atmospheric chemistry. Discovering why Venus is so similar to Earth and yet also so different reaches to the core of the Cosmic Vision questions:

  • How important is geology and atmosphere to sustaining life?
  • Are the initial conditions of planetary formation of key importance, or its later evolution?
Venus and Earth amidst artist impressions of newly discovered terrestrial exoplanets
Figure 2 : Venus and Earth amidst artist impressions of newly discovered terrestrial exoplanets

The science objectives of EnVision are to determine the nature of, and rate of change caused by geological and atmospheric processes, to understand why Venus has evolved so differently from Earth, despite their similar size and mass. EnVision will achieve these objectives by:

  • global stereo and interferometric digital elevation models at 20 m resolution, obtaining repeated InSAR imaging of potentially volcanically and/or tectonically active regions from up to one third of the surface at 20 m resolution, and high resolution (less than 5 m) multipolar imaging of specific targets from up to 10% of the surface;
  • detecting centimetre changes in surface elevation to constrain rates of geological change in potentially active target areas and estimating rates of weathering and surface alteration from InSAR decoherence data;
  • characterising the different stratigraphic and structural patterns of the subsurface and detecting subsurface structures not directly linked with the surface, for synergistic analysis of VenSAR and SRS data to study the evolution of the planet;
  • studying the volcanic phenomena, their impact on the geological evolution of Venusian topography, and constraining past and present geochemically-controlled atmospheric inputs and sinks; and
  • understanding impact crater degradation and obtaining gravity and geoid data at a geologically-meaningful scale, allowing competing models of interior processes and structure to be tested.

These data will provide an order of magnitude or more improvement on the 1989-1994 Magellan mission, and build on the tremendous success of the Venus Express mission and Europe's leading position in Venus science. The core payload required to deliver these objectives are:

  • VenSAR, an S-band phased array antenna, developed from the Sentinel-1 and NovaSAR-S radar payloads;
  • SRS, the Subsurface Radar Sounder, inheriting experience gained with MARSIS and SHARAD;
  • VEM, the Venus Emissivity Mapper, building on the success of VIRTIS and VMC on Venus Express; and
  • VIVO, the Venus Investigation of Volcanic Outgassing, a spectrometer for volcanic gases with heritage from NOMAD on ExoMars and SPICAV/SOIR on Venus Express.

Further payload to investigate complementary and more subtle atmospheric escape-related science goals may also be included, subject to spacecraft resource availability, funding, and competitive selection.