A NASA rocket launched from near the North Pole has officially detected something first hypothesized more than 60 years ago: an ambipolar electric field sheathing the planet.
According to an agency release, the field’s existence was proven with measurements by the Endurance mission, a rocket launched to measure the planet’s global electric potential. The electric potential was expected to have a very weak effect on charged particles in the atmosphere, making it difficult to detect. However, the property may also be a reason life as we know it manages on Earth when we’ve not spotted it anywhere else.
Endurance launched from Ny-Ålesund in Svalbard, Norway, in May 2022, after being delayed due to “apocalyptic winds and white-out conditions,” as one team member put it. It was a fitting start to the mission, given its namesake is the ill-fated vessel of Sir Ernest Shackleton that sank in 1914 after being stuck in Antarctic ice. The wreck of the Endurance was discovered in 2022 at the bottom of the Weddell Sea.
“Svalbard is the only rocket range in the world where you can fly through the polar wind and make the measurements we needed,” said Suzie Imber, a space physicist at the University of Leicester and co-author of the paper, in the NASA release.
Endurance achieved an altitude of 477 miles (768 kilometers) on its 20-minute flight before splashing down in the Greenland Sea. Now, the Endurance mission team has confirmed there is an electric field, the properties of which were reported in a paper published in Nature yesterday.
The rocket measured a change in electric potential of just .55 volts on its trip, indicating a weak electric field may be responsible for the polar wind, an outflow of particles from Earth’s atmosphere into space.
“A half a volt is almost nothing—it’s only about as strong as a watch battery,” said Glyn Collinson, principal investigator of the Endurance mission and lead author of the paper, in the same release. “But that’s just the right amount to explain the polar wind.”
The electric field is ambipolar—not because the wind exists at both poles, but because the tugging between electrons and ions is going both ways. The much-more-massive ions yank the electrons down towards Earth’s surface, while electrons pull ions upwards as they wriggle in the direction of space.
“We infer that [the field’s control of the ionosphere] increases the supply of cold O+ ions to the magnetosphere by more than 3,800%, in which other mechanisms such as wave–particle interactions can heat and further accelerate them to escape velocity,” the team wrote in the paper. “The electrostatic field of Earth is strong enough by itself to drive the polar wind and is probably the origin of the cold H+ ion population that dominates much of the magnetosphere.” In other words, this newly confirmed electrical field is a key driver in propelling ions out of Earth’s atmosphere and into space, shaping the composition of the magnetosphere.
The discovery of the electric field could help explain planetary evolution, too; worlds like Venus and Mars—now inhospitable—were once more like Earth. Venus’ hot, noxious atmosphere is thought to be the result of a runaway greenhouse gas effect. Mars’ arid wasteland once had lakes of liquid water on its surface. The very slight electric field on Earth may have shaped the evolution of the planet’s atmosphere, keeping our world livable while our neighbors became harsh.
