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Jupiter鈥檚 lightning is whistling and it鈥檚 pointing the way to the gas giant鈥檚 stores of water.

鈥淭here鈥檚 a lot that we don鈥檛 understand about Jupiter鈥檚 lightning, but from what we have observed it looks fairly similar to what we have on Earth,鈥� says William Kurth at the University of Iowa, who was part of two studies that mapped the lightning strikes happening across Jupiter between 2016 and 2017.

Kurth says that these lightning maps might help us figure out where the water is within Jupiter, and how much of it there is, because lightning in gas giants is believed to come from clouds of water.

When the Galileo probe dove into Jupiter鈥檚 atmosphere in 1995, it found much less water than we expected. 鈥淣ow it鈥檚 become evident that the probe fell into a dry spot in the atmosphere,鈥� says Kurth. 鈥淚t鈥檚 like some alien beings landing in the Sahara desert to find out how much water Earth has. It鈥檚 the totally wrong answer.鈥�

From the lightning maps, it seems like most of that 鈥榤issing鈥� water is in Jupiter鈥檚 northern hemisphere, with some in the south and almost none around the equator. The clouds are moved around by convection within Jupiter, so this could indicate that this churning is somehow directing heat preferentially towards the poles. 鈥淭hat鈥檚 another surprise,鈥� says Kurth.

Whistling dixie

Lightning strikes are made of powerful electrical currents flowing out of charged clouds. As it moves, the current creates the visible light that we might see during a storm. It also emits a range of radio waves. On Earth, those waves are emitted across the radio spectrum, but past Jupiter probes have only detected lightning-related radio waves at frequencies a million times lower than the highest-frequency lightning we see here.

It鈥檚 as if Jupiter鈥檚 emissions were sung out by a choir of only basses. At the time, researchers thought the high-frequency radio waves might be blocked by Jupiter鈥檚 ionised upper atmosphere, or maybe that the lightning strikes were slower-moving on Jupiter, in which case they would only produce lower-frequency waves.

But the Juno probe was able to look at lightning on Jupiter from a much closer vantage point than previous spacecraft. In its first 8 orbits around the planet, Juno鈥檚 microwave radiometer detected 389 lightning signals at the higher frequencies we see in signals from Earth鈥檚 lightning.

Another instrument aboard Juno detected more than 1600 lower-frequency lightning strokes, called whistlers because of their decreasing pitch as they travel. The lightning flash rate calculated from this data was about 1-30 flashes per square kilometre per year, much higher than previous estimations and closer to Earth鈥檚 lightning rate of about six flashes per square kilometre per year.

The choir of Jupiter鈥檚 lightning isn鈥檛 as sparse as we thought 鈥� and it鈥檚 not all basses. It鈥檚 got just as much range as lightning on Earth.

Read more: Fiery exoplanet may see a trillion lightning flashes in an hour