Thunderstorms on Jupiter are so strong that ammonia-rich hail, known as “mouse balls” can fall from the sky.
New observations by NASA’s Juno spacecraft on the gas giant planet could have implications for our understanding of giant planetary atmospheres in general, which are for the most part made of gas and are subject to much higher pressure than what we are on earth are known.
These observations also suggest that Jupiter has “shallow lightning”, which occurs in clouds with ammonia and water. This is very different from Earth, where lightning strikes in water clouds, according to a statement from NASA.
Related: Pictured: Juno’s great views of Jupiter
“Juno’s close-up flybys of the cloudheads showed us something surprising – smaller, shallow flashes – emerging at much higher altitudes in Jupiter’s atmosphere than previously thought possible,” leads Heidi Becker, Juno’s radiation monitoring researcher at NASA’s Jet Propulsion Laboratory in California, said in the same statement. Becker is also lead author of a new paper in Nature, one of three new studies describing Juno’s work.
Thunderstorms on Jupiter and Earth have one thing in common: these natural phenomena move water in the atmospheres of both planets. When NASA’s Voyager spacecraft first detected lightning at Jupiter in 1979, it was thought that both planets had similar types of lightning.
Voyager saw lightning in Jupiter’s cloud tops, suggesting that the phenomenon originated in deep water clouds. However, Juno’s new observations on night flashes on Jupiter reveal a more subtle story.
On Jupiter, thunderstorms are thought to form about 31 miles (50 km) below the visible bands and storms on the planet, where temperatures are close to the freezing point of water. Some of these storms are so powerful that they feed crystal water ice in the upper atmosphere of the planet.
“At these altitudes, ammonia acts as an antifreeze, lowering the melting point of water ice and allowing the formation of a cloud of ammonia-water liquid,” Becker added in the same statement. “In this new state, falling drops of ammonia-water liquid can collide with the rising crystals of water-ice and electrify the clouds. This was a big surprise, because ammonia-water clouds do not exist on earth.”
The shallow lightning may also show why ammonia appears to be missing (or removing) from Jupiter’s atmosphere, and why ammonia appears in various concentrations in Jupiter’s atmosphere.
“Previously, scientists knew there were small pockets of missing ammonia, but no one realized how deep these pockets went or that they covered most of Jupiter,” said Scott Bolton, chief researcher at Juno at the Southwest Research Institute in San Antonio, in same statement.
“We have trouble explaining the depletion of ammonia with ammonia-water rain alone,” Bolton added, “but the rain could not go deep enough to match the observations. I realized that a solid, like a hailstone, can go deeper and “When Heidi discovered shallow lightning, we knew we had evidence that ammonia mixes with water high in the atmosphere, and thus lightning was a key part of the puzzle.”
The “mushballs” and trampled ammonia are further described in work published in the Journal of Geophysical Research: Planets in Two Parts, Available over here en over here. When ice crystals combine with ammonia (a solid substance in the atmosphere of Jupiter), the ammonia creates an “antifreeze” effect and converts the ammonia from ice to liquid.
As the mushrooms fall into Jupiter’s lower atmosphere, they drag ammonia and water down with them, before finally evaporating in the warmer temperatures. “That explains why we don’t see much of it in these places with Juno’s microwave radiometer,” said Tristan Guillot, a Juno co-researcher at the University of Côte d’Azur in Nice, France, and lead author of the two-part paper on ammonia and the mushrooms, said in the NASA statement.
“When it did, the ammonia was not really missing; it was just being transported down while mantling itself by mixing with water,” Bolton added. “The solution is very simple and elegant with this theory: When water and ammonia are in a liquid state, they are invisible to us until they reach a depth where they evaporate – and that’s pretty deep.”
Juno arrived at Jupiter almost exactly four years ago, on July 4, 2016 better understand the origin and evolution of the planet. Juno’s findings inform not only our understanding of planets of solar system, but also exoplanets of gigantic giants, especially those of a similar size and formation history as planets in our solar system.
Editor’s note: This article was updated with new information, video and images from NASA.
Follow Elizabeth Howell on Twitter @howellspace. Follow us on Twitter @Spacedotcom and on Facebook.
