Jupiter is a planet of storms, but also a planet of mysteries. How can an expanse of the gas giant swirling with cyclones also be a desert?
Expect everything from a planet famous (or infamous) for things like its Great Red Spot and a strange, stormy pentagon that could pass for a formation of UFOs. Jupiter’s “ hot spots ” (first captured by NASA’s Galileo probe) have been a mystery that has remained in the dark until now. Now the Juno probe has had a different look. It used to be thought to be local deserts. What Juno beamed back suggests that these hot spots, which glow deceptively bright in the infrared, may not be that different from the rest of Jupiter – at least the part of Jupiter in which they exist. That entire area of the planet is a cosmic desert.
As it turns out, Galileo messed up without knowing. As it plunged into one of the hot spots in Jupiter’s northern equatorial region and discovered how dry and windy it was, astronomers back to Earth automatically assumed each hot spot was its own local desert. They go much deeper and further than that, if you ask Juno co-researcher Tristan Guillot.
“We see that the whole area has a low amount of ammonia and we realize that the hotspots may just disappear into the clouds,” Guillot told SYFY WIRE. “The storms we see in the JunoCam footage must have transported both ammonia and water deep down, not just where the hot spots are, but all around these latitudes.”
Juno has revealed that the hot spots have something to do with cracks in Jupiter’s thick clouds, which could allow the probe to see into the depths of Jupiter’s atmosphere, where it is hotter and drier than anywhere else. Another thing Juno saw was that a phenomenon known as shallow lightning was powered by these desert storms. For lightning to form, there must be a liquid in the atmosphere to enlarge particles and transfer charge. Shallow lightning is so strange because it can occur at atmospheric levels that are too cold to keep water in a liquid state. This is where ammonia comes into play. If you mix water and ammonia, you can keep water liquid so that lightning can ignite even in such a deep freezer.
It only gets weirder from here. Juno’s microwave instrument can no longer see water and ammonia when they join forces. Not only that, but they also produce alien hailstones that aren’t as scientific as mushballs. Giant storms created by water condensing much deeper in the atmosphere give rise to the formation of mushball. Shallow lightning literally illuminates where these storms form, something that could ultimately aid in understanding how heat travels within the planet. If humans could actually live on Jupiter, shallow lightning would be a terrible sign of mushballs incoming.
“Mushballs show that Jupiter’s atmosphere is very different than expected,” said Guillot. “Rather than being convectively unstable and homogeneously mixed, we now envision the deep atmosphere as moderately stable, with ammonia and water increasing as you go deeper.”
When mushballs get heavy enough, they fall through the atmosphere, leaving an area almost devoid of ammonia and water. They have to melt and evaporate to make the ammonia and water gas again, making them visible to Juno again. Guillot sees the behavior of ammonia and water in Jovian storms as analogous to slowly adding milk to water without mixing the liquids. The milk sinks to the bottom of the glass, just as water and ammonia sink through Jupiter’s atmosphere during a storm. The difference is that unlike a glass, Jupiter has no bottom – or surface that we know of. How deep ammonia and water can sink is something that needs further investigation. It could hypothetically sink all the way. Nobody knows.
What the Juno team needs to do now is figure out how efficient the mushball formation really is, and how it should be applied to Juno data. The probe has already given the Juno team an idea of how much water is hiding deep in Jupiter’s atmosphere. For a more accurate estimate, they will need to understand how water makes its way to the depths of other regions. Juno may demystify that as it gradually moves towards Jupiter’s north pole, which is thought to have vastly different properties that Guillot and his colleagues could tell about bizarre Jupiter weather.
“Our research has far-reaching implications,” he said. “All the planets in our solar system, as well as exoplanets, have a very bright atmosphere. The same process can occur when elements in these atmospheres condense. Understanding what is happening in Jupiter will be critical when we apply our models to interpret exoplanetary spectra that will soon be measured by the James Webb Space Telescope. “