The Juno spacecraft helped scientists study Jupiter's massive storms, which new research suggests can trigger the formation of hail-like 'mushballs' made of water and ammonia. Photo by NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill
Aug. 5 (UPI) -- Jupiter's atmosphere, like Earth's, is home to a dynamic water cycle driven by the movement of large storms.
New research suggests these storms are capable of producing hail-like stones made up of ammonia and water, according to a study published Wednesday in the journal JGR Planets.
"We've known since Voyager and Galileo that water storms develop in the planet because they are the only ones that can explain the strong convective clouds that have been observed to reach Jupiter's stratosphere," lead researcher Tristan Guillot, planetary scientists at the French National Center for Scientific Research, told UPI.
What scientists say they hadn't realized, until now, that these storms are capable of lofting water crystals so high into Jupiter's upper atmosphere -- to a region just 12 to 15 miles below the top of the planet's visible clouds.
Researchers came to this realization with the help of the Juno and two of the spacecraft's cameras, which helped scientists more precisely characterize the scale of Jupiter's lightning storms.
Juno instruments also helped scientists get a better sense of the abundance of ammonia inside Jupiter's atmosphere. The data collected by Juno's microwave radiometer showed Jupiter's ammonia is highly concentrated around the equator, but depleted and highly variable most everywhere else.
Researchers developed an atmospheric mixing model to study the relationship between Jupiter's storms and its ammonia distribution patterns, and to simulate the kinds of chemical phenomena Jupiter's massive storms might generate. Their analysis revealed the potential for the production of ammonia-rich hail -- or what they call "mushballs."
"We tested the model to account for what is going up and down in Jupiter and found that in order to account for Jupiter's low ammonia abundance at high latitudes, we had to include more storms there," Guillot said. "The frequency of these storms correlates with the frequency of lightning flashes as a function of latitude measured by Juno."
The simulations showed that Jupiter's massive storms push water crystals toward the planet's upper atmosphere, and the water ice comes into contact with ammonia. This, according to researchers, acts as an antifreeze, melting the water ice and allowing the water and ammonia to mix.
"We developed a model for Jupiter and realized that these special ammonia-water hailstones would form, grow and fall rapidly, therefore transporting the ammonia -- and water -- to great depth in the planet, explaining the deficit of ammonia to great depths observed by Juno everywhere except at the equator," Guillot said.
So far, the model remains theoretical, and doesn't quite generate data in agreement with all of Juno's observations. Guillot said his colleagues hope to continue refinement of the model, in addition to more detailed observations of Juno's atmosphere, will narrow the gap between the model's predictions and the observational data.
Though the energies of most space agencies have largely been concentrated on the exploration of rocky objects like Mars, moons and asteroids, the latest findings suggest the solar system's many exotic atmospheres are ripe for surprising discoveries.
"There's still a lot of mysteries -- among them how deep do condensates sink to in giant planets" Guillot said. "A full characterization of clouds and atmospheric dynamics, for example, by an orbiter and a probe would give us the keys to understand planets with hydrogen atmospheres. When we're trying to make sense of observations of exoplanets, this is essential."