‘Vapour on Venus will tell us if it's alive'

More than two-and-a-half decades after its last missions to Venus, NASA has planned a trip to Earth’s nearest neighbour. On June 2, the US space agency announced DAVINCI+ and VERITAS missions to the planet in 2028-30 under its Discovery Program, going on since 1992. Space agencies have explored Venus since the 1960s, but focus shifted around mid-1990s. Venus regained interest after researchers from the UK detected phosphine, a gas released through organic processes, in the Venusian atmosphere. A week after NASA, the European Space Agency announced a Venus mission later this decade. India and Russia, too, have been planning Venus probes. Described as Earth’s twin due to its similar size and density, Venus’s atmosphere is full of carbon dioxide and clouds of sulphuric acid with a surface temperature hot enough to melt lead. NASA’s DAVINCI+ (Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging) will drop a descent sphere to measure the gases in Venus’ air, while VERITAS (Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy) will orbit the planet to map its geological features. We’ll also learn about phosphine, THOMAS P WAGNER, who leads the Discovery Program, tells DAKSHIANI PALICHA in an interview. Excerpts:

NASA’s last mission to Venus, Magellan, ended in 1994. What renewed your interest in the planet after 27 years?

The Venus missions had been proposed primarily for NASA's New Frontiers programme, and then for Discovery, but they did not get picked. This is not because there wasn’t a desire to go back to Venus, it’s just that other proposals—for example, the Juno mission to Jupiter or the Osiris Rex, Lucy and Psyche missions aimed for asteroids—beat them. Venus was also not as big a priority as Mars, where people were eager to detect signs of life.

However, between Magellan and now, there has been amazing technological development. Radars are more sophisticated, as are the radiometers that will map the composition of Venus’s surface and measure the light it emits into space. The chemical instrumentation to measure the composition of the atmosphere is phenomenal; we can now measure components that are present in minute amounts, like noble gases, which are important in understanding the history of the atmosphere. This is why we picked missions to Venus now.

What scientific return do you expect from DAVINCI+ and VERITAS?

The missions we pick face strict competition. The process began two years ago; we had 18 proposals and we evaluated their science and implementation plans. We then narrowed them down to four. These teams then planned their missions at an even higher level of detail. We looked at their implementability, cost, NASA's budget, among other things. So while evaluating their scientific return, we do not just consider the science, but also how it would fit with our portfolio. Right now, we do not have other missions to Venus; we are also going to launch the James Webb Space Telescope to study exoplanets [planets that exist outside the solar system] soon. These missions would help with that.