High above the Earth’s North and South Poles, a steady stream of particles escapes from our atmosphere into space. Scientists call this mysterious outflow the “polar wind,” and for almost 60 years, spacecraft have been flying through it as scientists have theorized about its cause. The leading theory was that a planet-wide electric field was drawing those particles up into space. But this so-called ambipolar electric field, if it exists, is so weak that all attempts to measure it have failed – until now. br br In 2022, scientists traveled to Svalbard, a small archipelago in Norway, to launch a rocket in an attempt to measure Earth’s ambipolar electric field for the first time. This was NASA’s Endurance rocketship mission, and this is its story.