ESA has selected EnVision as its next Venus orbiter. Scheduled to launch atop an Ariane 6 rocket between 2031 and 2033, the robotic deep-space probe will carry out a comprehensive survey of Earth's sibling planet to learn why the two turned out so very different.
One of the great surprises of the Space Age was the discovery by the Early NASA Mariner probes that Venus and Earth, which seem so similar, are actually dramatically different. One common speculation in the first half of the 20th century was that, because Venus is a little smaller than the Earth and inside what we now call the habitable zone, the band in the solar system where liquid water can exist, it was very likely habitable. Some of the more imaginative ones even speculated that Venus was covered with tropical swamps inhabited by Venusian dinosaurs.
Instead, the flyby and orbiter probes revealed a dry world with a carbon dioxide atmosphere 90 times denser than the Earth's, sulfuric acid rains, and a surface temperature that is hot enough to melt lead. The question is, why? What factors led to Earth becoming a wet, habitable world, while Venus became so toxic?
ESA's fifth medium-class mission for its Cosmic Vision plan, Envision will work with upcoming NASA Venus orbiters and the US agency's Deep Space Network to study the planet from its core to its upper atmosphere to build up a comprehensive profile of Venus and its evolution, as well as answer questions like, is Venus still geologically active with live volcanoes?
For the survey, Envision will carry NASA's Venus Synthetic Aperture Radar (VenSAR) for mapping the surface, and the VenSpec-M, VenSpec-H and VenSpec-U spectrometers from various European space organizations, which will study trace gases in the atmosphere and on the surface that might be linked to volcanic activity. In addition, France will provide the Subsurface Sounding Radar (SRS) for probing the interior of the planet's crust, and France and Germany will conduct a radio science experiment to probe the structure of Venus and its gravitational field.
EnVision now moves into the Definition Phase, when the satellite's basic design and instruments will be selected before formal designing begins. After launching, the spacecraft will take 15 months to reach Venus and another 16 months to go into its final 92-minute circular orbit at an altitude between 138 and 336 miles (220 and 540 km) through a series of aerobraking maneuvers.
"EnVision benefits from collaboration with NASA, combining excellence in European and American expertise in Venus science and technology, to create this ambitious mission," says Günther Hasinger, ESA Director of Science. "EnVision further strengthens Europe’s role in the scientific exploration of the Solar System. Our growing mission fleet will give us, and future generations, the best insights ever into how our planetary neighborhood works, particularly relevant in an era where we are discovering more and more unique exoplanet systems."
The animation below shows EnVision deploying its instruments
Source: ESA