Scientists at NASA have uncovered evidence of a new electric field encircling Earth, a discovery that could shed light on the mysterious supersonic particle winds erupting from the planet’s poles.

Known as the “ambipolar electric field,” the elusive phenomenon may help explain why Earth was able to host life when other planets could not.

The search for the source of the electrical field stretches back to the 1960s, when space agencies first noticed strange occurrences during orbital missions over the poles. Spacecraft were subjected to sudden blasts of charged particles, traveling at supersonic speeds from the upper atmosphere.

“Something had to be drawing these particles out of the atmosphere,” Glyn Collinson of NASA’s Goddard Space Flight Center said, according to the Daily Mail.

Despite decades of observation, the exact cause of the “polar winds” remained a mystery. Researchers hypothesized that a planet-wide electric charge, situated about 150 miles above Earth’s surface, might be responsible.

At that altitude, atmospheric atoms break into negatively charged electrons and positively charged ions. Given that ions are significantly heavier than electrons, they should theoretically fall toward Earth due to gravity. However, the ambipolar electric field tethers these ions to electrons, dragging them upward and out of the atmosphere.

To test the new theory, NASA in 2016 initiated the Endurance Mission, developing a rocket capable of detecting minute voltage differences across vast distances. The mission launched from Svalbard, a remote Norwegian island near the North Pole that was chosen for its unique magnetic field lines that extend out into space.

“The field is generated by electrons, which have some thermal pressure that allows them to rise to higher altitudes on open field lines,” a co-author and space physicist at the University of Leicester, Suzanne Imber, said, according to the Mail.