Astronaut Thomas Pesquet took a photograph on October 8 from the International Space Station that captured something exceedingly rare. The photo seen below clearly shows a bright blue-white luminous event on the horizon of the Earth. Pesquet took the single frame showing the blue luminous event from a longer time-lapse.
While the photograph looks like some sort of explosion, it was not, and most people on the ground would probably have never noticed the event occurred. What Pesquet captured is called a “transient luminous event,” which is similar to lightning but strikes upward in the upper atmosphere of the planet. Another name for the event is upper-atmospheric lightning.
Transient luminous events are a group of related phenomena typically occurring during thunderstorms. While similar to lightning, they occur significantly higher than normal lightning and work differently. Different types of events that fall into the transient luminous event category include “blue jets” occurring in the lower stratosphere, triggered by lightning. For such an event to occur, lightning must propagate through a negatively charged area of thunderstorm clouds before reaching a positive region below.
If that occurs, lightning strikes upward, which causes a blue glow from molecular nitrogen. A phenomenon known as red SPRITES also exists. Red SPRITES is an electric discharge typically red in color that occurs high above a thunderstorm cell and is triggered by lightning from below. One interesting aspect of what Pesquet captured is that scientists weren’t convinced they existed only a few decades ago.
Pilots had observed phenomena of the sort before science agreed the phenomena existed. Today, we know not only do transit luminous events exist, but they also influence the climate. It’s unclear what type of event we see in the photograph taken by Pesquet aboard ISS. It is worth noting that phenomena of this type are very difficult to capture in photographs from the ground.