On July 6, 1989, scientists at the University of Minnesota were testing a low-light video camera intended for an entirely different rocket mission when, by pure accident, they captured two brief, glowing shapes hovering far above a distant thunderstorm. It was the first confirmed photographic evidence of something witnesses had been describing, in scattered and largely disbelieved accounts, for at least two centuries: massive, silent flashes of red light bursting far above storm clouds, at the very edge of space itself.
Background: Two Centuries of Disbelieved Sightings
Red sprites belong to a broader category scientists call Transient Luminous Events, or TLEs, brief electrical light displays that occur in Earth's upper atmosphere, roughly 50 to 90 kilometers up in the mesosphere, directly above active thunderstorms. The earliest documented sighting comes from an 1886 report by Toynbee and Mackenzie, with even looser anecdotal accounts stretching back as far as the 1730s. Remarkably, in 1925, Nobel laureate physicist C.T.R. Wilson proposed a theoretical explanation for the phenomenon involving electrical breakdown in the upper atmosphere, an idea that turned out to be broadly correct decades before anyone could actually confirm it.
The Accidental First Photograph
The breakthrough came almost entirely by chance. Researchers at the University of Minnesota were testing low-light camera equipment meant for an upcoming rocket flight when they happened to capture two brief glowing blobs above a nearby storm, the first confirmed photographic evidence of the phenomenon, published by researcher Davis Franz and colleagues in 1990. The discovery immediately raised an obvious question within the scientific community: given how large and vivid these events apparently were, why had no one properly documented them before? Researchers soon realized cameras aboard NASA's own space shuttle missions had already unknowingly recorded similar flashes years earlier, without anyone recognizing what they were looking at.
Naming and Understanding the Mechanism
Physicist Davis Sentman of the University of Alaska Fairbanks coined the name "sprite," drawing on the whimsical, elusive connotations of the mythical fairy creature, later formalized into a backronym: Stratospheric/mesospheric Perturbations Resulting from Intense Thunderstorm Electrification. Unlike ball lightning's still-contested physics, sprites' underlying mechanism is now understood with considerable precision. An unusually powerful positive cloud-to-ground lightning strike leaves behind a residual electric field reaching far up into the thin air of the mesosphere. That field accelerates free electrons, which collide with nitrogen molecules in the rarefied upper atmosphere, exciting them and producing a brief reddish glow as the molecules relax back to their normal state, a fundamentally different physical process from an ordinary lightning bolt, closer in mechanism to a fluorescent tube discharge than to a spark.
A Larger Family of Sky Phenomena
Sprites turned out to be only the most common member of a broader family of Transient Luminous Events discovered in the years following 1989, including blue jets, which shoot upward from storm cloud tops into the stratosphere, and ELVES, rapidly expanding rings of light. Researchers gave many of these playful, fairy-tale-inspired names, reflecting both their fleeting, otherworldly appearance and, by more than one scientist's own admission, an occasional sense of humor within the field. Sprites remain by far the most frequently observed and easiest to spot from the ground under sufficiently dark skies, far from light pollution.
Modern Citizen Science
NASA has since launched Spritacular, a crowdsourced citizen-science project built specifically to collect public sprite photography. As NASA atmospheric physicist Burcu Kosar has explained, countless striking images have been captured informally and shared online for years without ever reaching the scientific community that could actually use them, a gap the project is now working to close through ongoing public collaboration.
Weather & Sky Mysteries at a Glance
| Phenomenon | What's Observed | Leading Explanation | Status |
|---|---|---|---|
| Ball Lightning | Glowing sphere appearing during storms, lasting seconds | Vaporized soil silicon, confirmed by 2014 field spectroscopy | Partially explained; solid-object permeability unresolved |
| Red Sprites | Brief, high-altitude reddish electrical flashes above storms | Electron collisions with nitrogen, triggered by strong lightning below | Well understood; related TLE subtypes still being mapped |
| Morning Glory Clouds | Rare, massive rolling cloud formations | Specific atmospheric conditions over northern Australia | Understood in general terms; hard to predict precisely |
| St. Elmo's Fire | Glowing, crackling light on pointed objects during storms | Corona discharge from strong electric fields | Well explained scientifically |
| Brown Mountain Lights | Unexplained lights reported over a North Carolina ridge | Disputed; multiple partial explanations proposed | Unresolved |
Theories and Explanations
The quasi-electrostatic field mechanism, confirmed. Decades of follow-up research since 1989 have refined and confirmed the core explanation: a powerful positive lightning strike's residual electric field accelerates electrons that excite nitrogen molecules high in the mesosphere, producing the characteristic red glow.
The full TLE family, still being mapped. While sprites themselves are well understood, the precise relationship between sprites and related phenomena like blue jets, ELVES, and gigantic jets, including the exact conditions that determine which type occurs, remains an active area of ongoing atmospheric research.
Broader atmospheric effects, still under study. Researchers continue investigating what influence sprites and other TLEs may have on upper-atmosphere chemistry, electrical properties, and even radio signal propagation, questions without full scientific consensus on their overall significance yet.
Possible sprites on other worlds. Some researchers have explored, through theoretical modeling and laboratory experiments, whether similar electrical discharges could occur in the atmospheres of Venus or gas giant planets like Jupiter, a genuinely speculative extension of Earth-based sprite research.
The Curious Connection
Red sprites offer a sharp contrast to this series' opening entry on ball lightning. Where ball lightning's core mechanism remains genuinely contested even after a landmark 2014 field observation, red sprites' underlying physics has been understood with steadily increasing precision since shortly after their accidental 1989 discovery. Both phenomena belong to the same broad category, strange, brief electrical events in Earth's atmosphere, yet pointing real scientific instruments at the sky produced two very different outcomes: one mystery substantially solved, the other still only partially explained.
That contrast is exactly the pattern this series will keep exploring, alternating between atmospheric phenomena science has largely figured out and others that continue to resist full explanation, much like ball lightning's own stubborn unsolved details.
Frequently Asked Questions
What are red sprites?
Red sprites are a type of Transient Luminous Event, brief reddish electrical flashes that occur in Earth's upper atmosphere, roughly 50 to 90 kilometers up, directly above powerful thunderstorms.
When were red sprites first confirmed?
Scientists at the University of Minnesota captured the first confirmed photographic evidence of sprites on July 6, 1989, by accident, while testing camera equipment for an unrelated rocket mission.
What causes red sprites?
An unusually powerful positive cloud-to-ground lightning strike leaves behind a residual electric field that accelerates electrons high in the mesosphere, causing them to collide with and excite nitrogen molecules, producing the characteristic red glow.
Why are they called "sprites"?
Physicist Davis Sentman coined the name for its whimsical, elusive connotation, later formalized into a backronym for Stratospheric/mesospheric Perturbations Resulting from Intense Thunderstorm Electrification.
Can you see red sprites from the ground?
Yes, under sufficiently dark skies far from light pollution, sprites can be seen as brief flashes above distant thunderstorms, and NASA's Spritacular project now encourages members of the public to photograph and submit their sightings.