Summary
When NASA announced it would spend $1 billion developing two new missions to Venus—the agency’s first visits in decades to Earth’s hothouse twin—planetary scientists were elated, and not just because a long wait had ended. A dramatic shift in thinking about the planet over the past few years has made a visit even more enticing. Venus was once thought to have boiled off all its water almost as soon as it was born 4.5 billion years ago, turning into the parched, hostile world of today. But recent climate modeling has now suggested the planet’s slow rotation would allow planet-spanning cloud decks to form, reflecting the Sun’s attack and allowing Venus to host expansive oceans for billions of years—a nearly perfect setting for life. The two spacecraft, both selected as part of NASA’s Discovery line of competed missions, will arrive later this decade, scouring the surface and atmosphere for signs of past water and plate tectonics—and clues to why Venus ultimately declined into an inferno.