Using data gathered by ESA’s Venus Express researchers have determined what likely happened to Venus’ water: it was “zapped” away by a surprisingly strong electric field generated by the planet’s atmosphere and the incoming solar wind. Without a protective magnetosphere like Earth has, Venus’ upper atmosphere directly interacts with energetic particles streaming out from the Sun. The result is an electric field that’s at least five times more powerful* than those that might exist on Earth or Mars, strong enough to strip away oxygen ions—one of the two key ingredients for water.
It’s truly an electrifying discovery. (When you’re done groaning, read on…)
Venus formed in relatively the same environment around the Sun as Earth, and is of similar size, mass, and composition. It most likely had liquid water on its surface early in its development, perhaps even oceans, over four billion years ago. But something happened at Venus that moved all of its surface liquid into its atmosphere, creating a dense, global blanket of clouds that traps heat from the Sun and today finds its bone-dry surface baking in 800-degree temperatures and crushed beneath enormous pressures.
With the discovery of an electric field in Venus’ atmosphere—the first such measurement at any planet— scientists now have an idea where Venus’ water ended up: blown into space ion by ion.
This means that Venus could very well have had more water in its early days than once thought; it also means that “Earthlike” rocky exoplanets in other systems star have one more thing we have to consider when determining their potential habitability—an electric field.
“Water has a key role for life as we know it on Earth and possibly elsewhere in the Universe,” says Håkan Svedhem, Venus Express Project Scientist at ESA. “By suggesting a mechanism able to deprive a planet close to its parent star of most of its water, this discovery calls for a rethink of how we define a ‘habitable’ planet, not only in our Solar System, but also in the context of exoplanets.”
*This electric field, although strong enough to strip ions away from Venus’ atmosphere, is still relatively weak compared to what we are accustomed to on Earth—”only roughly the same as a single wind turbine, and it’s spread out over hundreds of kilometers of altitude” according to Glyn Collinson from NASA’s Goddard Flight Space Center, lead author of this study. This is why it’s taken this long to make a confirmed detection of such a field around a planet.