Our planet has many fields: corn fields, gravitational fields, and magnetic fields. However, for decades, scientists have been unable to measure Earth’s electric field. That is, until now.
Earth’s electric field was first hypothesized 60 years ago when scientists flying over the north and south poles detected that particles were leaving the atmosphere into space at supersonic speeds. It was predicted that some weak field had to be drawing these particles out, but detecting such a field was too technologically advanced for the time.
The discovery was made by a NASA’s Endurance mission, a part of which was a suborbital rocket launched from Svalbard, Norway, just a few hundred miles from the North Pole, in May 2022. Nineteen minutes later, the rocket crashed down in Greenland, having successfully measured the electric field over the north pole. Since then, the data has been analyzed by NASA scientists, who recently published their results.
The field is in one of the upper layers of our atmosphere, called the ionosphere. Positively charged ions and negatively charged electrons in the atmosphere are tethered together by an electric field between them. The field is described as being bidirectional or “ambipolar,” with the heavy ions pulling the electrons down with them as they fall with gravity and the lighter electrons lifting the ions as they try to escape into space. Some of these ions are lifted high enough to escape into space, causing the stream of particles at the poles that were measured decades ago.
The field is extremely weak, only 0.55 volts, a lower voltage than your watch battery. For this reason the miniscule changes in potential have to be felt over miles, as Endurance was able to measure. This required a special device, which was invented specifically for the Endurance mission. The team, led by Glyn Collinson of NASA’s Goddard Space Flight Center in Maryland, developed a new instrument called a photoelectron spectrometer. This device measures the energy spectra of electrons in the upper atmosphere, which can be compared to previous calibrations to measure the electric field. Despite the field being so weak, it is still powerful enough to propel ions into space, which have been measured in this experiment.
Further research will involve looking into how the electric field could have shaped the development of life on Earth, the formation of water, and allow us to learn more about other planets. Any planet with an atmosphere should have an electric field, even a weak one, so this recent discovery opens a new area of research in planetary science. Scientists are specifically looking at what this new data can illuminate about the differences between Earth and Venus. The European Space Agency discovered in 2016 that Venus had a strong 10-volt electric field, which likely removed positively charged oxygen particles from the atmosphere and prevented water from forming. Further investigations will be done to study why Earth’s electric field is substantially weaker, and why water was still able to form. This field is as fundamental to Earth as our gravitational or magnetic field, and reanalyzing our planet’s history with this newfound context will be an upcoming challenge for scientists.
