Eerie green flash: Unusual lightning observed on Jupiter

NASA's Juno spacecraft has detected unusual lightning bolts on Jupiter.

Lightning strikes have been observed in the high atmosphere of the gas giant Jupiter, ignited in huge ammonia clouds.

Although lightning has been detected in the planet's atmosphere before, this is the first time it has been observed in the highest cloud layers, alongside a bright green flash.

The newly discovered lightning originated in a physical environment where the formation of lightning was previously thought to be impossible.

The water droplets needed as charge carriers should not actually exist in Jupiter's high atmosphere, since temperatures below minus 70°C are far too cold for liquid water. However it occurred due to the clouds of the gas planet containing a lot of ammonia.

This gas acts like an antifreeze on the ice crystals, causing them to melt. The resulting solution of ammonia and supercooled water becomes a charge carrier when it collides with solid ice crystals, causing electrical voltage to be discharged.

Unlike on Earth, the high-altitude thunderstorms on the gas planet do not occur at the equator, only at high latitudes around the north polar region.

A NASA animation simulates flight through the massive thunderstorms in Jupiter's high atmosphere. It shows the scattered light from the newly discovered flashes of light in the clouds and delves into the planet's gigantic atmospheric jet.

It continues through Jupiter's turbulent cloud masses, past the spray of ammonia rainwater and lightning. Real footage from the Juno camera was combined with a computer-generated animation.

Researchers also discovered that the ammonia-water solution on Jupiter creates a special type of hail. Like on Earth, this is shell-shaped and grows through updrafts and downdrafts in the clouds.

The turbulence compresses the semi-liquid ammonia-water solution into a kind of slush, which is repeatedly covered by a thin crust of water ice.

When these slush balls become too large and heavy they fall into deeper layers of the atmosphere, similar to hail in the Earth's atmosphere.

The Juno spacecraft was launched in 2011 and reached the gas giant in 2016 for its mission originally estimated to last 20 months in orbit around Jupiter. The mission has already been extended twice and will continue until at least 2025.

In addition to the planet itself, the probe is also taking aim at Jupiter's icy moons. Researchers suspect that beneath the kilometre-thick ice crusts of these moons are entire oceans of liquid water, in which life could even have developed.