There are spirits high above us, with colors coming from space

In June 2019, scientists in Spain went looking for ghosts haunting the skies above the Mediterranean Sea. These green-tinted strings, which danced above pink-red lightning at extremely high altitudes during thunderstorms, had only been discovered in May of that year. What were they? The only way to know was to catch one.

But that would prove to be a difficult task. These ghosts are aptly named: they are difficult to see with the naked eye and appear only a heartbeat tens of kilometers above the ground.

“Seeing a ghost is very difficult,” he said Maria Passas-Varoa researcher at the Institute of Astrophysics of Andalusia in Spain.

But on September 21, 2019, they finally caught one with a specialized camera: a green ghost flickering at the crown of a jellyfish-shaped maelstrom of fuchsia lightning, 50 miles above the sea. And after painstakingly untangling the different wavelengths of light emitted by the ghost, the scientists revealed its elemental composition.

This is evident from a study published in the journal on Tuesday Nature communicationrevealed Dr. Passas-Varo and her colleagues that the ghost’s pale emerald skin color arose in part from excited oxygen, similar to the green glow of auroras; Nitrogen also plays a role.

But the biggest contribution was made by another element: iron. That was a surprise because the metal was ultimately brought in from space.

A better understanding of ghosts and other short-lived lightning-like entities could help scientists interpret the difficult-to-parse chemistry and physics of Earth’s upper atmosphere.

“There are layers of metals dancing” in and above thunderstorms, said Dr. Passas-Varo.

Ghosts are a type of transient luminous event, or TLE, which was first described by scientists in 1989. TLEs may include blue jets, firing upward from thunderclouds, as well as crimson lightning in the upper atmosphere which can come in many forms such as carrots and jellyfish, and is known as a whip.

TLEs “are like fireworks,” said Dr. Passas-Varo. And little is definitively known about them — especially about ghosts, the first of which was spotted atop a sprite storm over Oklahoma in May 2019.

To capture their own minds, her team pointed a spectrographic camera – a camera that can use light to determine chemistry – at the upper layers of the atmosphere from an observatory in Castellgalí, Spain. All they could do was wait for sprite thunderstorms to appear, cross their fingers and hope that at least one sprite would be briefly decorated with a ghost, and that their camera was pointed in the right spot.

Finally, they found one fluttering around on a jellyfish ghost.

“It was a matter of luck,” said Dr. Passas-Varo.

This was powered largely by extraterrestrial iron, not atmospheric oxygen. The camera also revealed the presence of nickel, sodium and silicon. The complex chemical soup responsible for this ghost even added a yellow-orange hue to the green glow.

All of these elements often come from micrometeoroids and deep space dust grains that almost continuously enter the upper atmosphere. This means that ghosts can effectively be seen as interplanetary visitors.

Still, some researchers said not too many conclusions should be drawn from the new paper’s findings.

“The metallic traces are interesting, but I warn you that this was just a single event,” he said Chris Vagasky, a lightning researcher at the University of Wisconsin-Madison who was not involved in the new work. To see if all the ghosts are iron-powered ghosts, he added: “It would be nice to see the results of multiple ghosts.”

He has no doubt that the search for ghosts and other TLEs will continue – largely because these phantoms are inherently seductive.

“It’s really incredible to think that there is so much more happening during a thunderstorm than what you can see or hear,” said Dr. Vagasky.