Scientists have recorded the first direct measurement of a faint electric field in Earth's upper atmosphere, termed the ambipolar electric field. This discovery, made during NASA's Endurance mission launched in May 2022 from Svalbard, Norway, could significantly influence our understanding of atmospheric dynamics and life-supporting conditions on Earth.
Led by Glyn Collinson from NASA's Goddard Space Flight Center, the mission has confirmed the existence of this weak electric field, measured at just 0.55 volts. It plays a crucial role by maintaining the balance of charged particles, preventing them from escaping into space.
When sunlight interacts with atmospheric atoms, it ejects negatively charged electrons, which drift away. The remaining heavier positively charged oxygen ions create a faint electric field that helps keep the atmosphere stable. This field also energizes lighter particles, such as hydrogen, facilitating their escape from Earth's gravitational influence—a phenomenon known as the polar wind.
Published in the journal Nature, the findings provide new insights into Earth's atmospheric evolution and its capacity to support life. David Brain, a planetary scientist at the University of Colorado Boulder, notes that comparing electric fields across different planets may illuminate why Earth remains habitable while others, like Mars and Venus, do not.
In response to these findings, NASA has approved a follow-up mission called Resolute, aimed at further studying planetary electric fields and their effects on atmospheric escape and habitability.