Mars is so last year. After NASA announced on 2 June that it will launch two probes to Venus before the end of the decade, the European Space Agency (ESA) today joined the party by selecting EnVision, another orbiter mission to our cloud-wrapped twin, for launch in 2031. The €610 million EnVision is the latest medium-class mission in ESA’s science program.
Compared with Mars, Venus has seen fewer visits from robotic spacecraft, but increased interest in climate change and Earth-like exoplanets has prompted researchers to ask why Venus is now a scalding hot greenhouse oven with a sulfuric acid atmosphere, after starting out so similarly to Earth. ESA’s Venus Express, which operated from 2006 to 2014, helped find hinds of ancient oceans and active volcanoes on the planet. Firming up that evidence is a key aim for EnVision, says lead scientist Richard Ghail of Royal Holloway, University of London. “The pattern of volcanoes tells us how the planet works,” he says.
Although there is some overlap in the aims and instruments of the NASA and ESA missions, Ghail says, “They do all fit together and in a sense, they are in the right order.” NASA’s VERITAS will provide a detailed global map of the planet’s topography, whereas DAVINCI+ will establish compositional “ground truth” by parachuting a probe through the atmosphere. EnVision will follow up by zooming in to understand how surface activity affects atmospheric dynamics, Ghail says.
Venus’s thick cloud cover means optical cameras can’t see much, but other wavelengths can penetrate the murk. EnVision will use an infrared spectrometer to seek out hot spots on the surface that could indicate active volcanoes. It will use radar to map the surface, looking for signs of lava flows. Ultraviolet and high-resolution infrared spectrometers will then look for water vapor and sulfur dioxide emissions, to see whether smoldering volcanoes are driving cloud chemistry today.
Ghail thinks space agencies have recognized that Venus deserves the same layered approach used on Mars, where global mapping missions have been followed by more targeted observations. “The discovery by Venus Express that there may be volcanism,” he says, “has made it a more interesting place to be.”