Sprites and elves have been spotted dancing in the upper atmosphere of Jupiter. These aren鈥檛 mystical beings, but two types of flashes of light called transient luminous events (TLEs), and it is the first time they have been seen on a planet other than Earth.
The unpredictable flashes were spotted by accident, when a team led by Rohini Giles at the Southwest Research Institute in San Antonio, Texas, was looking through ultraviolet images collected by NASA鈥檚 Juno spacecraft as it orbits Jupiter.
Juno rotates to allow its various instruments 鈥� including an ultraviolet imaging spectrometer 鈥� to capture information about the planet. 鈥淲e happened to notice that there was a tiny bright flash that was present in one spin, but not in the next,鈥� says Giles. It lasted just a millisecond or two.
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The researchers created an algorithm to spot similar flashes in their existing data and found a total of 11 with similar properties.
The flashes couldn鈥檛 have been caused by lightning, which has been seen on Jupiter before, because they were too high in the atmosphere. This means they are likely to be TLEs 鈥� short flashes of plasma caused by electrical discharge at high altitudes.
On Earth, several types of TLE have been spotted, including those called elves and sprites, named after their mystical appearance. Sprites on Earth are red. They appear in a flash, lasting up to 2 seconds, that looks like a jellyfish shape in the sky with a ring around the top and tentacle-like streams underneath. But the mechanisms behind them remain a bit of a mystery.
鈥淎lthough there were eyewitness accounts from earlier, it wasn鈥檛 until 1989 that a sprite was photographed for the first time,鈥� says Giles, 鈥渟o TLEs are still a relatively new field of study, even on Earth.鈥�
Jupiter and Earth have different atmospheric compositions, electron distributions and magnetic fields, so comparing TLEs on the two planets can teach us how these came about. 鈥淚f we are able to observe TLEs on other planets, like Saturn, in the future, that will provide even more data points,鈥� says Giles.
On Earth, TLEs are thought to play a role in the global electric circuit that links the planet鈥檚 surface to the ionosphere through electric fields generated by constant thunderstorm activity. But Jupiter doesn鈥檛 have a conductive surface like Earth.
鈥淚t鈥檚 fascinating to see how the common processes in atmospheric electricity are reproducible at different planetary environments,鈥� says Karen Aplin, an atmospheric and space scientist at the University of Bristol, UK, who wasn鈥檛 involved in the study. 鈥淭hese could ultimately offer us ways to understand our own planet鈥檚 weather better.鈥�
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